ALBERT

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉China is the world’s largest coal producer and consumer. Despite extensive studies on coal-burning pollution, the effect of raw coal pollutants caused by transportation and turnover on soil along the road received little attention. The main purpose of the study was to clarify the biogeochemical response of soil ecosystems to raw coal pollution.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The raw coal and unpolluted soil from the coal distribution area in Xuanhua, China were collected for the incubation experiments. Combined with the determination of soil physicochemical properties, including pH, electric conductivity, soluble ions, dissolved organic carbon, and available heavy metals, the biogeochemical responses of soil to raw coal pollution, such as soil enzyme activities (β-glucosidase, alkaline phosphatase, and Urease), microbial community composition, and soil respiration, were systematically studied. In addition, a q-PCR analysis of the urease was performed to clarify the inhibitory mechanism of urease by coal pollution. Furthermore, a simple field investigation was carried out to confirm the incubation results.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Raw coal pollution not only changed the soil physicochemical properties but also made the available Zn, Ni, and Co accumulate significantly. A positive priming effect in soil with the low-dose raw coal addition was trigged, but soil respiration rate and soil enzyme activity, such as β-glucosidase and alkaline phosphatase, were inhibited to different degrees with the increased pollution. Urease activity also decreased under the higher coal contamination, which was due to inhibition of 〈em〉ureC〈/em〉 gene expression. In addition to the slight soil acidification caused by coal pollution, microbial communities and diversity was also found to be affected. The relative abundances of the microorganisms related to urease, alkaline phosphatase, and β-glucosidase changed accordingly. The incubation results are in good agreement with the field survey results.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Low-dose raw coal pollution can trigger the soil positive priming effect. However, as the coal pollution increased, the β-glucosidase, alkaline phosphatase, and urease in the soil were inhibited to varying degrees. The compounding effects of soil acidification, increased electric conductivity, and the accumulation of available heavy metals such as Zn, Ni, and Co are the key causes for the biogeochemical response of soil to coal pollution.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Humic substances are the relatively stable and recalcitrant pool of soil organic carbon in the agricultural system. Humic acid (HA) is an active part of soil humic substances. However, little information exists on how structural characteristics of HA evolved with fertilization years in Black Soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soil samples were collected in 1997, 2002, 2008, and 2012 from the Long-term Fertilization Station of Black Soil. The methods of 〈sup〉13〈/sup〉C-nuclear magnetic resonance spectroscopy, elemental composition analysis, and infrared spectroscopy were employed to analyze the structure of HA.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Long-term fertilization had no significant (〈em〉P〈/em〉 〉 0.05) effect on the ratio of O and S to C in HA. The ratio of H to C in HA increased with fertilization years after the application of organic manure (M) single or combined with chemical NPK fertilizers. The ratios of aliphatic C to aromatic C, and alkyl C to O-alkyl C in soil HA increased by 7.72% and 20.3%, respectively, in MNPK and M treatments, whereas NPK treatment declined the ratio of aliphatic C to aromatic C by 2.67% compared with CK treatment.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The HA structure tends to become aliphatic and simplified with years of organic manure combined with NPK fertilizers. To save costs, organic manure was only applied once within the period of crop rotation and was combined with NPK every year to satisfy crop demands for soil nutrients.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Soil organic carbon (SOC) in mountainous regions is characterized by strong topography-induced heterogeneity, which may contribute to large uncertainties in regional SOC stock estimation. However, the quantitative effects of topography on SOC stocks in semiarid alpine grasslands are currently not well understood. Therefore, the purpose of this research study is to determine the role of topography in shaping the spatial patterns of SOC stocks.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soils from the summit, shoulder, backslope, footslope, and toeslope positions along nine toposequences within three elevation-dependent grassland types (i.e., montane desert steppe at ~ 2450 m, montane steppe at ~ 2900 m, and subalpine meadow at ~ 3350 m) are sampled at four depths (0–10, 10–20, 20–40, and 40–60 cm). SOC content, bulk density, soil texture, soil water content, and grassland biomass are determined. The general linear model (GLM) is employed to quantify the effects of topography on the SOC stocks. Ordinary least squares regressions are performed to explore the underlying relationships between SOC stocks and the other edaphic factors.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉In accordance with the present results, the SOC stocks at 0–60 cm show an increasing trend in respect to the elevation zone, with the highest stock being approximately 37.70 g m〈sup〉−2〈/sup〉 in the subalpine meadow, about 2.07 and 3.41 times larger than that in the montane steppe and montane desert steppe, respectively. Along the toposequences, it is revealed the SOC stocks are maximal at toeslope, reaching to 14.98, 31.76, and 49.52 kg m〈sup〉−2〈/sup〉, which are also significantly larger than those at the shoulder by a factor of 1.38, 2.31, and 1.44, in montane desert steppe, montane steppe, and subalpine meadow, respectively. Topography totally is seen to explain about 84% of the overall variation in SOC stocks, of which 70.61 and 9.74% are attributed to elevation zone and slope position, while the slope aspect and slope gradient are seen to plausibly explain only about 1.84 and 0.01%, respectively.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The elevation zone and the slope position are seen to markedly shape the spatial patterns of the SOC stocks, and thus, they may be considered as key indicating factors in constructing the optimal SOC estimation model in such semiarid alpine grasslands.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Multivariate statistical analysis was used for the correlation of 〈sup〉238〈/sup〉U, 〈sup〉232〈/sup〉Th, and 〈sup〉40〈/sup〉K equivalent activities to geochemical data from soil samples collected at depths from 0 to 20 and 20 to 40 cm in an agricultural area.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A total of 154 soil samples were used for determining radionuclide equivalent activities, pH, clay and organic matter contents, and available phosphorous, potassium, calcium, magnesium, copper, zinc, iron, and manganese concentrations.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Activities ranged from 31.0 to 124 Bq kg〈sup〉−1〈/sup〉 for 〈sup〉40〈/sup〉K, 2.50 to 20.9 Bq kg〈sup〉−1〈/sup〉 for 〈sup〉238〈/sup〉U, and 0.40 to 17.1 Bq kg〈sup〉−1〈/sup〉 for 〈sup〉232〈/sup〉Th. At depths from 0 to 20 cm, clay and organic matter contents ranged from 14.0 to 88.0 and 0.60 to 4.60%, respectively. Available phosphorous, potassium, calcium, magnesium, copper, zinc, iron, and manganese concentrations ranged from 1.80 to 80.0, 36.0 to 667, 40.1 to 1923, 12.1 to 328, 0.80 to 26.1, 0.50 to 23.5, 29.0 to 112, and 30.0 to 76.0 ppm, respectively. The pH at the same depths ranged from 5.70 to 7.20. At depths of 20 to 40 cm, these ranges were from 14.0 to 92.0 and 0.50 to 4.30%, and 1.00 to 60.0, 24.0 to 364, 60.1 to 2024, 12.2 to 328, 0.70 to 28.8, 0.50 to 21.3, 2.50 to 148, and 2.30 to 100 ppm, respectively. The pH at these depths ranged from 5.70 to 7.30.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Important correlations were found between radionuclide equivalent activities and geochemical data at both depths by multivariate statistical analysis.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉In contaminated streams, understanding the role of streambank and streambed source contributions is essential to developing robust remedial solutions. However, identifying relationships can be difficult because of the lack of identifying signatures in source and receptor pools. East Fork Poplar Creek (EFPC) in Oak Ridge, TN, USA received historical industrial releases of mercury that contaminated streambank soils and sediments. Here, we determined relationships between the contaminated streambank soils and sand-sized streambed sediments.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Field surveys revealed the spatial trends of the concentrations of inorganic total mercury (Hg) and methyl mercury (MeHg), Hg lability as inferred by sequential extraction, particle size distribution, and total organic carbon. Statistical tests were applied to determine relationships between streambank soil and streambed sediment properties.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Concentrations of Hg in streambank soils in the upper reaches averaged 206 mg kg〈sup〉−1〈/sup〉 (all as dry weight) (〈em〉n〈/em〉 = 457), and 13 mg kg〈sup〉−1〈/sup〉 in lower reaches (〈em〉n〈/em〉 = 321), while sand-sized streambed sediments were approximately 16 mg kg〈sup〉−1〈/sup〉 (〈em〉n〈/em〉 = 57). Two areas of much higher Hg and MeHg concentrations in streambank soils were identified and related to localized higher Hg concentrations in the streambed sediments; however, most of the streambank soils have similar Hg concentrations to the streambed sediments. The molar ratio of Hg to organic carbon, correlation between MeHg and Hg, and particle size distributions suggested similarity between the streambank soils and the fine sand-sized fraction (125–250 μm) collected from the streambed sediments. Mercury in the fine sand-sized streambed sediments, however, was more labile than Hg in the streambank soils, suggesting an in-stream environment that altered the geochemistry of sediment-bound Hg.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study revealed major source areas of Hg in streambank soils, identified possible depositional locations in streambed sediments, and highlighted potential differences in the stability of Hg bound to streambank soils and sediments. This work will guide future remedial decision making in EFPC and will aid other researchers in identifying source–sink linkages in contaminated fluvial systems.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The relationship between soil macropore and plant roots warrants special attention because it influences the behavior of water in soil. However, the influence of shrub roots on soil macropores in shrub-encroached grasslands is poorly understood. The objectives of this study were to quantify soil macropores and root architecture in a shrub-encroached grassland in northern China, and to reveal the relationship between shrub roots and soil macropore.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉In this study, treatments were performed that corresponded to three successional states of the shrub 〈em〉C. microphylla〈/em〉 L. with three different shrub densities. At each site, three undisturbed soil cores were excavated under the shrub canopies, and a Philips medical scanner was used to simultaneously visualize and quantify the soil and root architectures.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Strong positive correlations between root volume, length, and surface area and the solid surface/solid volume ratio were found, and greater root growth was noted in more porous soil. The results highlighted that the soil macropore characteristics corresponded well with the root characteristics of the soils for the three treatments. Soil macroporosity and macropore volume increased with increasing shrub root network density. In addition, the influence of plant roots on soil macropores increased with increasing shrub encroachment. The study confirmed that the large number of macropores found in the soils under shrubs was attributed to the great degree of root development there.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The greater degree of macroporosity under shrubs was attributed to the larger root network density, which might cause greater amounts of water to be concentrated in the deep soil layer by macropore flow under shrub patches. The influence of plant roots on soil macropores increased with increasing shrub encroachment.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Biological nitrogen fixation (BNF) plays an important role in nitrogen cycling by transferring atmospheric dinitrogen to the soil. BNF is performed by symbiotic and asymbiotic nitrogen-fixing microorganisms. However, the abundance, activity, and community structure of diazotrophs under different nitrogen fertilizer application rates and how root exudates influence diazotrophs remain unclear.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉〈sup〉15〈/sup〉N-N〈sub〉2〈/sub〉 and 〈sup〉13〈/sup〉C-CO〈sub〉2〈/sub〉 labeling, DNA-based stable isotope probing (SIP), and molecular biological techniques were used in this study. The abundance, activity, and structure of symbiotic and asymbiotic diazotrophs under different nitrogen fertilizer applications in paddy soil were investigated.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉We found that the nitrogen fixation capacity in milk vetch (〈em〉Astragalus sinicus〈/em〉 L.) and 〈em〉nifH〈/em〉 gene abundance in the root nodules were significantly higher in the low-nitrogen treatment than in the control (zero) and high-nitrogen treatments. Nitrogen-fixing bacteria were abundant in the soils with a high biodiversity. Soil 〈em〉nifH〈/em〉 gene sequences were dominated by 〈em〉α〈/em〉-, 〈em〉β〈/em〉-, and 〈em〉δ〈/em〉-〈em〉proteobacteria〈/em〉, as well as by 〈em〉Cyanobacteria〈/em〉. The relative abundance of 〈em〉α〈/em〉-〈em〉proteobacteria〈/em〉 was lower, and the relative abundance of 〈em〉Cyanobacteria〈/em〉 was higher under high nitrogen. Incubation of soil with 〈sup〉13〈/sup〉CO〈sub〉2〈/sub〉 and subsequent DNA-SIP analysis demonstrated that OTU65 from 〈em〉α〈/em〉-〈em〉proteobacteria〈/em〉 was relatively more abundant in heavy fractions of the 〈sup〉13〈/sup〉C-labeled soils than that in the unlabeled soils, indicating that 〈em〉α〈/em〉-〈em〉proteobacteria〈/em〉 may prefer rhizodeposition carbon to other organic carbon. However, OTU24 and OTU73 from 〈em〉δ〈/em〉-〈em〉proteobacteria〈/em〉 had relatively high abundances in light fractions both in the 〈sup〉13〈/sup〉C-labeled and unlabeled samples, indicating that 〈em〉δ〈/em〉-〈em〉proteobacteria〈/em〉 may prefer other soil organic carbon to rhizodeposition carbon.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The results suggested that soil N availability and rhizodeposition strongly modified the microbial communities of nitrogen-fixing bacteria. Moderate nitrogen application increased the symbiotic biological N fixing activity in the 〈em〉Astragalus sinicus〈/em〉 L. rhizosphere. The BNF activity in the legume-rhizobia system is regulated by the exchange of organic C and N nutrient between the host plant and N-fixing bacteria.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The potential for using biochar to reclaim degraded urban land into productive land needs to be verified to address the incipient loss of agricultural land.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A pot experiment was conducted to evaluate the effect of wheat straw biochar (with four application rates including 0, 0.5%, 1%, and 2% 〈em〉w〈/em〉/w biochar to soil) on selected soil properties and crop growth (paddy rice was grown followed by wheat) in a compacted urban homestead soil (Anthrosol). Nitrogen use efficiency and ammonia volatilization were determined using stable isotope methodologies.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Wheat straw biochar amendments elevated the soil pH, total C, and C/N ratio, and significantly lowered (〈em〉P〈/em〉 〈 0.05) the soil bulk density by 12.0–17.7% with doses of 1–2%. Increasing doses of biochar (1–2%) increased ammonia volatilization by 91.4–107.0% during the flooded rice season, which resulted in significantly lower (〈em〉P〈/em〉 〈 0.05) rice yield. This was reflected in the reduction of fertilizer 〈sup〉15〈/sup〉N use efficiency, which was 32.6–76.0% lower (〈em〉P〈/em〉 〈 0.05) than the control. However, the following wheat yield was significantly increased (〈em〉P〈/em〉 〈 0.05) by 23.0% with 2% biochar amendment, while there were no differences in ammonia volatilization between biochar amendments and the control.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Application of wheat straw biochar to a reclaimed urban Anthrosol increased seasonal flooded rice ammonia volatilization; however, no effect on ammonia volatilization was detected from the following aerobically grown wheat. The soils had a lower bulk density following biochar amendment and improved pH, which may have resulted in the higher wheat yield.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Altitudinal gradients have been recognized as a natural experiment to assess the structure and functions of above - and below-ground ecosystem under global climate change. Nutrient stoichiometry is tightly linked both the above-and below-ground functioning, but how the altitudinal gradients affect nutrient stoichiometry among plant and soil systems remains unclear.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soil samples were collected at 17 sites along an altitudinal gradient from 1362 to 3320 m in the North Slope of Taibai Mountain. These samples represent three different climate zones, including a warm temperate zone, a cold temperate zone, and an alpine cold zone. Soil moisture (SM), soil temperature (ST), and the concentrations of carbon (C), nitrogen (N), and phosphorus (P) in soil and leaves were determined.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The C and N in soil and leaves were higher at medium altitudes than that at low or high altitudes, while P concentrations increased significantly as altitude increased. The C: N ratio in soil and leaves was not significantly affected by altitudinal gradients, but the C: P and N: P ratios were lower at high altitudes. In particular, the leaf N:P ratio at high altitudes was less than 12, suggesting an increase in N limitation along altitudinal gradients. Moreover, except the C: N ratio, soil C: N: P stoichiometry was significantly related to leaf C: N: P stoichiometry, and both showed closed relationships with ST and SM.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉These results suggest that stoichiometric characteristics appear to be closely linked with climatic factors, and improved knowledge of C: N: P stoichiometry patterns along altitudinal gradients will be indispensable to a comprehensive understanding of the influences of climate change on ecosystems.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Ammonia oxidation is the rate-limiting step in nitrification. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) are the key drivers of the nitrogen cycle. Chinese milk vetch (MV) has the potential to substitute for part of chemical fertilizer, but it remains unclear how MV is able to replace N fertilizer. The purpose of this study was to investigate the rice yield, soil properties, potential nitrification activity (PNA), abundances, and community structures of ammonia oxidizers in a paddy soil under MV combinations of different rates of chemical fertilizer.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉This study was conducted at a long-term Experimental Station of the Fujian Academy of Agricultural Sciences, Fuzhou, China. The treatments included a control (without fertilization), NPK (chemical fertilizer), MF80 (MV plus 80% NPK), MF60 (MV plus 60% NPK), and MF40 (MV plus 40% NPK). Soil samples were collected after the rice harvest. We determined the soil physico-chemical properties and PNA. The abundances and community structures of AOB and AOA were assessed using their ammonia monooxygenase (〈em〉amoA〈/em〉) genes. Quantitative PCR was used to determine the gene abundance, and Illumina Miseq sequencing was used to explore the diversity of AOB and AOA.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉MV significantly increased the soil organic matter and PNA in comparison to the NPK. The available nitrogen content was higher in the MV treatments than in the control and NPK. Compared to the NPK, the application of MV increased the AOB abundance but decreased that of AOA. The abundance of AOA was higher in the control and NPK, but lower in the MV treatments than that of AOB. PNA was significantly positively correlated with the AOB abundance. The primary dominant OTU of the AOB group was 〈em〉Nitrosospira〈/em〉. MV significantly affected the AOB community, while no impact on the AOA community was observed. Principal coordinate analysis showed that the MV treatments were significantly distinct from those of the control and NPK. Redundancy analysis indicated that the soil OM, TN, AN, pH, and PNA were significantly correlated to the AOB community structure.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study demonstrated that MV combined with reduced chemical fertilizer would contribute to the improvement of soil fertility and PNA, resulting in rice yield comparable to that of the NPK. MV had a stronger effect on the AOB community than did chemical fertilizer. AOB played a more important role than AOA in the ammonia oxidation in this soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉One of the most fragile agro-ecosystems in Iran is represented by dry farming lands on steep hillslopes that occupy ca. 54% of the national agricultural lands. Therefore, in order to reduce loss of fertile soil from these lands, it is important to apply effective soil conservation strategies. This study used cesium-137 (〈sup〉137〈/sup〉Cs) and excess lead-210 (〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉) measurements to assess the effectiveness of soil conservation practices in controlling soil erosion in Kouhin, Qazvin Province of Iran.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soil samples were collected from two adjacent hillslopes with and without conservation agriculture practices. The managed site benefited from conservation practices, including controlled grazing, terraces, and contour farming for 50 years. The unmanaged site was under cultivation without agricultural conservation practices. At the managed site, both 〈sup〉137〈/sup〉Cs and 〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉 activities were measured. Only 〈sup〉137〈/sup〉Cs activity was measured for the unmanaged site.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Conservation practices performed at the managed site were effective in minimizing soil erosion, i.e., net soil erosion rates provided by 〈sup〉137〈/sup〉Cs measurements were only 4.6 Mg ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉 at the managed site, compared to 12 Mg ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉 for the unmanaged site. By using the 〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉 approach, net soil loss and sediment delivery ratio in the managed site were 12.3 Mg ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉 and 60%, respectively.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Soil redistribution magnitudes established from 〈sup〉137〈/sup〉Cs inventories are associated with a period extending from 1963 to the time of sampling, while those obtained from 〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉 measurements are related to the past 100 years. However, 〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉 measurements are expected to be more sensitive to erosive events that occurred during the last 15 to 20 years and this could reflect the higher estimate of erosion rate provided by this radionuclide for the managed site. The increasing trend seems to suggest a possibility that the higher soil losses estimated by the 〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉 measurements are a result of increasing climate variability during the last two decades. However, further investigation would be needed to confirm this hypothesis.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉River channel sediments have been widely used to trace current and historical pollution in fluvial systems, although they are not the only media employed for that purpose. The current practice in such use of sediments from sampling strategy, sample pre-treatment and geochemical data processing frequently includes unsubstantiated and redundant steps (e.g., sieving by sub-millimetre meshes) and neglects certain relevant aspects (insufficient attention to what is actually sampled). The aim of this work was to improve that state and to remove redundant steps that make research more time-consuming and potentially introduce biases.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The work presents data obtained in the identification of pollution sources in a small catchment with three tributaries (the Ploučnice River, the Czech Republic). The sediments were manually sampled in river channels in sites of recent accumulation of fine solids transported by the river. The samples were pulverised and analysed by X-ray fluorescence spectroscopy. The sediments are composed mostly of silt and sand with most chemical elements, including risk elements “diluted” by quartz and detritic organic matter, which are perfectly suited for geochemical normalization to correctly process compositional data. We avoided statistical tools based on Gaussian distribution, such as means and standard deviations, and instead used median-based statistics better fitting the known properties of geochemical datasets.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Sediment sieving to sub-millimetre-size fractions was replaced by geochemical normalization best with Fe and possibly with Rb and Ti, with Al showing implausible performance. The normalization produces grain-size invariant compositional data. The performance of geochemical normalization and downstream variations of risk element concentrations (Pb and Zn) were tested by median-based criteria. Median smoothing of normalized risk element concentrations produced easily interpretable downstream variations of the pollution extent that were independent of grain-size effects and were robust towards the occasional presence of outliers.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Channel sediments are suitable for fluvial pollution monitoring if biased routines are avoided. The paper can inspire specialists who plan to perform environmental monitoring and desire to simplify their work and produce robust and unbiased estimates of pollution sources in fluvial systems under anthropogenic pressure. A similar approach could be tested for monitoring of pollution by further elements and hydrophobic organic compounds, except for the need to choose another normalizing element or TOC.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aims of this study are to investigate historical PAH deposition through the analysis of PAHs in bulk peat cores and reveal the different distribution of PAHs in 〈em〉Sphagnum〈/em〉 and 〈em〉Ledum〈/em〉 peat from peat cores.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Peat cores from Jingjiang peatland are collected, and 〈em〉Sphagnum〈/em〉 peat samples are manually separated from bulk peat. The remaining bulk peat samples are defined as “〈em〉Ledum peat〈/em〉.” 〈sup〉137〈/sup〉Cs is used to date the peat cores. PAH contents as well as physicochemical property of 〈em〉Sphagnum〈/em〉 and 〈em〉Ledum〈/em〉 peat are determined.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The PAH deposition rates measured in the bulk peat cores range from 3.5 to 12.8 ng cm〈sup〉−2〈/sup〉 year〈sup〉−1〈/sup〉, which are different in both absolute values and trends from those of nearby sediment cores. Concentrations of PAHs in 〈em〉Sphagnum〈/em〉 and 〈em〉Ledum〈/em〉 at the surface are similar, indicating the accumulation ability by adsorption and uptake between two species of plants are similar. However, at depths of 5–30 cm, concentrations of PAHs in 〈em〉Sphagnum〈/em〉 peat are higher than those in 〈em〉Ledum〈/em〉 peat, which can be attributed to their different PAH accumulation abilities or to different PAH degradation rates. An increase in PAHs/TOC ratios with depth in 〈em〉Sphagnum〈/em〉 peat indicates that PAHs are resistant to degradation in 〈em〉Sphagnum〈/em〉 peat. While a significant positive correlation between C/N and PAHs in 〈em〉Ledum〈/em〉 peat suggests that PAHs may be degraded during peat decomposition in 〈em〉Ledum〈/em〉 peat.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study finds a difference in PAH concentrations between 〈em〉Sphagnum〈/em〉 and 〈em〉Ledum〈/em〉 peat. The results suggest that peat quality rather than microbials results in a difference in both PAH accumulation and degradation in peat cores.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The objective of this study was to evaluate the mutual relations between the soil organic matter (SOM) fractions: fulvic acids (FA), humic acids (HA), humins (HN), black carbon (BC) and the polycyclic aromatic hydrocarbons (PAH) accumulation level in agricultural soils influenced by historical and actual anthropopressure. The research allowed to indicate which fractions of SOM are the major sequestration sinks for PAHs after they are naturally introduced into the soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soil samples were collected from the upper layer of agricultural soils (〈em〉n〈/em〉 = 41), and basic physicochemical properties (pH〈sub〉KCl〈/sub〉, total carbon, total nitrogen and clay content) were determined. The SOM was characterised by the total organic carbon content and humic substances, including HA, FA and HN, determined by an adapted method recommended by the International Humic Substances Society. The extracts of HA and FA were analysed for carbon content using a liquid CN analyser, while HN constituted the soil carbon in the residue after FA and HA extraction. The content of BC was analysed by dry combustion at 375 °C for 24 h (CTO375); the remaining carbon was determined via combustion in an elemental analyser.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉In all soils, significant positive relations between PAH concentrations and TOC content (〈em〉r〈/em〉 = 0.73, 〈em〉p〈/em〉 〈 0.001) as well as HN (〈em〉r〈/em〉 = 0.71, 〈em〉p〈/em〉 〈 0.001) and BC (〈em〉r〈/em〉 = 0.86, 〈em〉p〈/em〉 〈 0.001) were noted. Relations among PAHs, HN and BC were statistically significant only in soils with TOC content ≥ 12 g kg〈sup〉−1〈/sup〉, while they were not observed for soils with TOC content 〈 12 g kg〈sup〉−1〈/sup〉. The links between HN and PAHs were stronger for low-molecular (two and three rings)-weight PAHs (〈em〉r〈/em〉 = 0.77, 〈em〉p〈/em〉 〈 0.05) than for high-molecular (≥ four rings) PAHs (〈em〉r〈/em〉 = 0.68, 〈em〉p〈/em〉 〈 0.05). Contrary to HN, the BC faction showed higher correlations with high-molecular-weight PAHs (〈em〉r〈/em〉 = 0.92, 〈em〉p〈/em〉 〈 0.001). FA and HA showed no significant relationship with hydrocarbons.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Different SOM fractions might possess divergent binding capabilities and dissimilar binding strengths to PAHs. The different proportions and sorption capacities of BC and HN in relation to PAHs of different molecular weight are the result of varying structure, i.e. polar and non-polar functionalities in sorption domains and pore-size structures of these fractions. The high correlation between BC and higher-molecular PAHs may be a result of their co-emission, while the stronger relationships between HN and lower-molecular PAHs are directly related to their higher mobility and easier diffusion to stable SOM fractions.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Following ground-based skidding operations, understory vegetation and litter layer are commonly damaged or displaced by the movement of machines and timber on the machine operating trails, thus leaving the area vulnerable to increased runoff flow and sediment yield. One of the interim options available to suppress runoff and soil loss is the application of litter mulch directly after mechanized harvesting operations. The goal of the study is to assess the effects of broadleaves litter mulch on runoff and sediment yield immediately after rainfall events on a severely compacted skid trail in a mixed forest in Hyrcanian forests, northern Iran.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The study included six treatments (undisturbed area, untreated trail, and four levels of litter rate; 0.42, 0.81, 1.31, and 1.69 kg m〈sup〉2〈/sup〉 referred to as LR1, LR2, LR3, LR4, respectively) and two levels of trail gradient (10% and 20%), replicated in three plots (7 m long × 1 m width).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The highest runoff values of 1.54 and 1.33 mm were measured at trail gradients of 20 and 10% for the untreated trail, respectively. The litter mulch application resulted in runoff decreasing by 49%, 67%, 75%, and 79% in the LR1, LR2, LR3, and LR4 treatments, respectively. The highest values of runoff coefficient were measured in the untreated trail (U; 4.6%), followed by LR1 〉 LR2 〉 LR3 ≈ LR4 treatments. Sediment yield in the untreated treatment was 7.32 g m〈sup〉−2〈/sup〉 on the 10% gradient trail and 6.15 g m〈sup〉−2〈/sup〉 on the 20% trail gradient. Sediment yield values in the LR1, LR2, LR3, and LR4 treatments were decreased by 76%, 85%, 90%, and 93%, respectively, compared to the untreated treatment.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉By increasing the litter rate, runoff and sediment yield responses significantly decreased as the rainfall increased. The net differences between the tested litter rates and the runoff and sediment yield reductions were higher with increasing rainfall intensity.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Intercropping of chili pepper (〈em〉Capsicum annuum〈/em〉 L.) with corn (〈em〉Zea mays〈/em〉 L.) is one of the main valuable intercropping patterns. However, the potential contribution of arbuscular mycorrhizal (AM) fungal hyphal networks is still poorly understood. The purpose of this work was to resolve the changes of AM fungal propagation and colonization in the pepper/corn intercropping systems due to the constitution of hyphal networks and the networks’ effects on plant nutrient uptake and interspecific competitive relations.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉An 18-week pot experiment on an unsterilized soil was carried out to test mycorrhizal performance and P acquisition of chili pepper and sweet corn (〈em〉Zea mays〈/em〉 L. 〈em〉var〈/em〉. 〈em〉rugosa〈/em〉 Bonaf.) in two compartments, which were absolutely separated (Sep) by polyvinyl chloride (PVC) layer or semi-separated (Semi-Sep) by nylon mesh (30 μm) screen that only allows the passage of AM fungal hyphae but not plant roots. Root mycorrhizal colonization rates and the biomasses and P concentrations of shoots, roots, and fruits of pepper and corn were all measured. The total P acquisition of each crop per pot and the acquisition ratio of one to two crops were assessed. Soil pH, organic C, total P, available P, AM fungal abundance, and acid phosphatase activity were also tested.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉In the Sep system, root mycorrhizal colonization, P acquisition amount, shoot biomass, and rhizosphere AM fungal abundance of corn were all higher (〈em〉P〈/em〉 〈 0.05) than those of pepper, but soil available P concentration was lower (〈em〉P〈/em〉 〈 0.05) in corn compartment than in pepper one. Compared with Sep, Semi-Sep had higher (〈em〉P〈/em〉 〈 0.05) mycorrhizal colonization rates with both intercrops and higher (〈em〉P〈/em〉 〈 0.05) soil acid phosphatase activity and AM fungal abundance in corn and pepper compartments, respectively. Semi-Sep decreased (〈em〉P〈/em〉 〈 0.05) soil available P concentrations with both compartments, but did not narrow the difference of soil available P concentration between compartments, suggesting there was no gradient diffusion of soil available P between compartments. Semi-Sep increased (〈em〉P〈/em〉 〈 0.05) the P acquisition ratio and fruit yield of pepper, but not corn.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Constitution of hyphal networks increased mycorrhizal colonization with both intercrops, and corn supplied part of photosynthetic C for increasing AM fungal propagules in pepper compartment by gradient expansion since AM fungi formed better symbioses with corn. Hyphal networks increased pepper fruit yield via improving P distribution to pepper, but acquired relatively higher P from corn compartment via elevating the soil acid phosphatase activity, suggesting enhanced P competitive ability of pepper against corn upon hyphal networks.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Intercropping can increase crop production and maintain soil organic matter levels in soil. The underlying mechanisms are associated with above- and below-ground nutrient (e.g., nitrogen) availability, uptake, and use efficiency. The aims of this study were to identify the effect of the N availability improvement on yield of intercrops and to explore soil N transformation rates in rhizosphere soil of wheat/faba bean intercrops, as compared with their sole crops.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉In a field experiment, crops productivity was measured and rhizosphere soils of intercropped and monocropped wheat/faba bean were collected to examine changes of soil gross N transformation rates via a nitrogen-15 (〈sup〉15〈/sup〉N) incubation study.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Intercropping significantly increased the productivity. Grain yields of intercropped faba bean and wheat were 11.4 and 34.2% higher than those of the corresponding monocrops, respectively. The gross and net rates of organic N mineralization and nitrification, as well as the gross mineral N immobilization rates were considerably greater in intercropping compared to the sole cropping system. The results suggested that the increased grain yield during intercropping was related to an improved capacity of N supply and conservation in soils via an intensification of the mineralization-immobilization turnover (MIT) and intercropping enhanced mineral N availability.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our findings demonstrated that wheat/faba bean intercropping was able to significantly increase the productivity of both companion crops under subtropical condition. The environmental implication of NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 leaching and runoff under monocropping conditions could be alleviated by adopting an intercropping management.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The geochemistry of pore waters from sediments deposited in the semi-enclosed bay of the Zrmanja River estuary, encompassing two small interconnected basins, the Novigrad Sea and the Karin Sea, was investigated. The conducted research aimed to identify diagenetic processes occurring in surficial bottom sediments and to assess the impact of these reactions on trace element concentrations in the overlying water.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Sediment pore waters were extracted from sediment cores in a nitrogen atmosphere. Multielemental analysis of prepared samples was performed by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). All samples were analysed for the total concentration of 15 elements (As, Ba, Co, Cr, Fe, Li, Mn, Mo, Ni, Rb, Sb, Sr, Ti, U and V).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Results indicate enrichment of sediment pore waters in the majority of measured elements relative to the estuary water. Degradation of organic matter and dissolution of Mn-Fe-oxyhydroxides under suboxic and anoxic conditions were identified as principal sources of dissolved cations in the studied pore waters. While sediments from the Novigrad Sea act as a permanent geochemical sink, the estimated fluxes for the Karin Sea sediments indicate transfer of certain elements from the sediment back to the water column, amounting to ~ 0.3 μg m〈sup〉−2〈/sup〉 day〈sup〉−1〈/sup〉 for Co, Ti and U; ~ 0.7 μg m〈sup〉−2〈/sup〉 day〈sup〉−1〈/sup〉 for As; between 1 and 5 μg m〈sup〉−2〈/sup〉 day〈sup〉−1〈/sup〉 for Mo, Ni and Ba; and ~ 70 μg m〈sup〉−2〈/sup〉 day〈sup〉−1〈/sup〉 for Fe and Mn.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉In the Zrmanja River estuary, the observed differences in the sediment pore water geochemistry and the role of the sediments in terms of mass exchange at the sediment-water interface could not be solely attributed to the sediment particle characteristics, but are considered to be a combined effect of organic matter input and local hydrogeological setting.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Here, the roles of sediment components in perfluorooctane sulfonate (PFOS) adsorption onto aquatic sediments and relevant adsorption mechanisms were investigated in terms of adsorption isotherms and influences of TiO〈sub〉2〈/sub〉 nanoparticles (NPs) contamination.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Due to the complexity of the sediments, instead of randomly selecting different component sediments, the selective dissolution method was used to better explore the effects of sediment compositions, such as sediment organic matter (SOM) and ferric oxides (dithionite–citrate–bicarbonate [DCB] Fe), and TiO〈sub〉2〈/sub〉 NPs pollution on PFOS adsorption. Mathematical equations (Freundlich, Langmuir, and Temkin) were used to describe the adsorption behavior of PFOS on different sediments and adsorption mechanisms of multiple pollutant interactions. Moreover, the characterization methods of zeta potential, nitrogen (N〈sub〉2〈/sub〉) adsorption–desorption, and scanning electron microscopy (SEM) analysis, as well as Fourier transform infrared (FT-IR) spectroscopy, explained effects of the sediment components and TiO〈sub〉2〈/sub〉 NPs on PFOS adsorption properties in view of physicochemical theories.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The adsorption isotherms of PFOS on six tested sediments were all nonlinear (Freundlich model, 〈em〉R〈/em〉〈sup〉2〈/sup〉 〈em〉=〈/em〉 0.992~1.000). The Freundlich sorption affinities (〈em〉K〈/em〉〈sub〉F〈/sub〉) of PFOS on S (original sediments), S1 (sediment organic matter (SOM)-removed S), and S2 (ferric oxides (DCB Fe)-removed S1) were 0.232, 0.179, and 0.120, respectively. Both SOM and DCB Fe influenced the physicochemical properties of the sediments, e.g., zeta potential, specific surface area, and permanent negative charge. The addition of TiO〈sub〉2〈/sub〉 NPs increased the 〈em〉K〈/em〉〈sub〉F〈/sub〉 of PFOS for S, S1, and S2 by approximately 9.9%, 14.5%, and 26.7%, respectively, by increasing the zeta potential and specific surface area (〈em〉S〈/em〉〈sub〉BET〈/sub〉, 〈em〉S〈/em〉〈sub〉ext〈/sub〉, and 〈em〉S〈/em〉〈sub〉micro〈/sub〉) and by changing the water and oil properties of the three sediments. However, the addition of TiO〈sub〉2〈/sub〉 NPs decreased the linearity of the sorption isotherm (1/n). FT-IR spectroscopy showed that hydrophobicity, ion exchange, surface complexation, and hydrogen bonding interactions (non-fingerprint region) could all play a role in PFOS sorption onto tested sediments. However, the hypothesis of hydrogen bonding to promote PFOS adsorption on sediment layer silicates (fingerprint region) should be studied further.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The content of both SOM and DCB Fe affected the physicochemical properties of sediment. Both SOM and DCB Fe showed a positive relationship with sorption of PFOS on sediment. The addition of TiO〈sub〉2〈/sub〉 NPs increased PFOS sorption by altering the sediment surface properties. Hydrophobic interactions certainly impelled and ligand and ion exchange and hydrogen bonding (non-fingerprint region) could promote PFOS sorption on the sediments.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Soil and water erosion from high rock fragment content disturbed soil accumulation severely threatens ecological security. Evaluation of the quantitative influence of rock fragment content on soil erosion processes was the basic research for soil and water conservation.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Field simulation scouring experiments were conducted on the disturbed soil accumulation experimental plot. A 10 × 1-m〈sup〉2〈/sup〉 plot with 28 gradients was established on Changwu Experimental Station in the Loess Plateau, China. Tap water was applied at the top of the plot with the four different flow discharge rates of 1.3 × 10〈sup〉−4〈/sup〉, 1.7 × 10〈sup〉−4〈/sup〉, 2.1 × 10〈sup〉−4〈/sup〉 and 2.5 × 10〈sup〉−4〈/sup〉 m〈sup〉3〈/sup〉 s〈sup〉−1〈/sup〉 to simulate surface runoff processes. The experimental plots underlying surfaces were filled with different rock fragment content of 20%, 40% and 0%. The soil used in these experimental plots was a silty loam from the disturbed soil accumulation formed by expressway construction in the loess plateau areas. The disturbed soil accumulation site was located near the G70 Fujian–Yinchuan expressway and the vegetation cover was very low. The mean diameter of rock fragments was 22 mm in these experiments, and the rock fragments were unsmooth, angular crushed stone taken from the quarry in the Changwu County.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that rock fragment content of 20% and 40% could significantly decreased runoff and sediment (〈em〉P〈/em〉 〈 0.05), although there was no significantly different between 20 and 40%. The rock fragments decreased mean flow velocity by 43 to 55% in mean flow velocity compared to the pure soil. Furthermore, the flow was laminar flow in the rock fragments slope. The rock fragments significantly decreased flow shear stress (52–89%), stream power (63–89%), unit stream power (41–59%), runoff kinetic energy (67–88%) and unit energy of the water-carrying section (81–89%) compared with the pure soil. With increased rock fragment content, the rill erodibility decreased. The rill erodibility was estimated to be 1.4 × 10〈sup〉−3〈/sup〉 s m〈sup〉−1〈/sup〉, 0.7 × 10〈sup〉−3〈/sup〉 s m〈sup〉−1〈/sup〉 and 0.5 × 10〈sup〉−3〈/sup〉 s m〈sup〉−1〈/sup〉, under the condition of pure soil, rock fragment content of 20% and 40%, respectively.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Low rock fragment content (〈 40%) in disturbed soil accumulation significantly decreased runoff and sediment. With the rock fragment content increased, the rill erodibility was decreased. Appropriate rock fragment content could be used to control soil erosion on disturbed soil accumulation in practice. The important parameters from this study will be helpful for disturbed soil accumulation erosion prediction model establishment.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Ammonia oxidation is an important process in the removal of ammonia generated from feed and metabolic wastes in aquaculture systems. Considering the biogeochemical importance of ammonia oxidation in bioaugmented zero water exchange aquaculture systems, the diversity and abundance of bacterial and archaeal ammonia-oxidizing communities were analyzed in three selected ponds at different time intervals during the culture period, to unravel the key environmental factors influencing their distribution in the system.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The diversity and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in three tropical bioaugmented zero water exchange (ZWE) shrimp culture systems were analyzed using ammonia monooxygenase A (〈em〉amo〈/em〉A) gene from the sediment metagenome during different phases of culture. The environmental factors associated with the variability in bacterial and archaeal 〈em〉amo〈/em〉A gene abundance and diversity were elucidated using RDA and Pearson correlation analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Ammonia-oxidizing archaea (AOA), 〈em〉Nitrosopumilus〈/em〉 sp., 〈em〉Nitrosospharea〈/em〉 sp., and ammonia-oxidizing bacteria (AOB), 〈em〉Nitrosomonas〈/em〉 sp., were the dominant ammonia-oxidizing communities in the ZWE ponds studied. AOA shared 41 OTUs, and the maximum distribution was influenced by dissolved oxygen in the system, whereas AOB shared 4 OTUs. The copy numbers 〈em〉amo〈/em〉A gene determined using qPCR showed that the AOA 〈em〉amo〈/em〉A gene was 10- to 100-fold abundant than AOB 〈em〉amo〈/em〉A gene. Gene abundance of AOA was positively related to total organic carbon (TOC) and salinity of sediments, and the temperature had a negative impact on bacterial 〈em〉amo〈/em〉A gene abundance. The dissolved oxygen and TOC had a negative and redox potential a positive impact on the diversity of AOA, whereas pH had a negative impact on the diversity of AOB.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The ammonia-oxidizing archaeal communities dominated the bioaugmented zero water exchange aquaculture systems compared to bacteria based on the abundance and diversity analysis using 〈em〉amo〈/em〉A gene sequence-based OTU analysis and gene copy numbers. Dissolved oxygen, total organic carbon, and Eh of the sediments contributed to the distribution and abundance of AOA group in the ZWE ponds. This study points to the importance of environmental management in these culture systems for maintaining ammonia-oxidizing populations for optimal ammonia removal. The relative contribution of the archaea and bacteria to ammonia oxidation in these systems is to be further resolved along with that of anammox and comammox bacteria, which would help to develop appropriate biostimulation or bioaugmentation strategies for the management of these sustainable aquaculture production systems.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Phosphorus (P) pollution is a significant environmental problem in lakes, especially in lakes highly impacted by human activities, e.g., Honghu Lake. Years of farming activities have led to a complex occurrence of P in the sediment which has not been studied in detail. Iron redox cycling is a key mechanism controlling P adsorption–desorption behavior, and its study is an effective means of assessing P dynamics, which could provide basic theoretical data for the control of internal phosphorus in such lakes.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The high-resolution ZrO-Chelex DGT (ZrO-Chelex diffusive gradients in thin films) and HR-Peeper (high-resolution dialysis sampler) techniques were used to assess labile P, labile Fe, and soluble reactive P (SRP) in five sediment samples from four functional areas of Honghu Lake. The temperature, pH, and dissolved oxygen levels of water samples were measured in situ using a portable water quality analyzer, and the dissolved organic carbon (DOC) concentration was analyzed with a TOC analyzer after 0.45 μm membrane filtration. Total Fe concentrations were determined using the phenanthroline colorimetric approach. Sediment porosity was calculated based on weight loss after drying for 6 h at 105 °C.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉One-dimensional changes in labile P and Fe in different functional areas of the lake were quite heterogeneous, and there was a significant linear correlation between labile P and Fe near the sediment–water interface (SWI). Sediment samples HH-2 and HH-5 exhibited positive P diffusion flux (〈em〉F〈/em〉) and tended to be a P source, while sites HH-1, HH-3, and HH-4 tended to take in P from overlying water. The ratio (R) of labile P to SRP was used as an indicator of potential soluble reactive P release from sediments into the surrounding water and initially increased at four sampling sites, then decreased deeper in the sediment except at site HH-4.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The results indicated that the tendency of P released from sediments or uptake from overlying water was distinct in different functional areas and that iron redox cycling was a key mechanism controlling P dynamics in the sediments of Honghu Lake. Thus, the iron–phosphorus relationship can provide an accurate assessment of P release processes in a surface water environment.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Iron plaque (IP) formation via radial oxygen loss (ROL) of wetland plant has been predominantly recognized as the reason for heavy metal sequestration in the rhizosphere. However, the same contribution of the microbes living in a potential rhizoplane biofilm matrix has not been comprehensively elucidated. In this review, we proposed a conceptional model of the wetland plant rhizoplane biofilm and summarized the possible pathways therein for heavy metal precipitation and iron-sulfur cycle termination.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉After an introduction of the effects of IP and microbes on the phytoremediation of heavy metal-contaminated wetland, the distribution of rhizospheric bacteria and different metal speciations resulted from wetland plant ROL were demonstrated. Based on the studies of microflora in the rhizosphere and IP, coupled with the ROL nature, we proposed an existence of rhizoplane biofilm with a special structure that could contribute to the rhizospheric iron-sulfur cycle termination by the production of heavy metal precipitates (metal sulfides).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The ROL leads to the diffusion of oxygen with a decreasing gradient from the root surface (rhizoplane) to the bulk soil, allowing the formation of an unconventional rhizoplane biofilm comprising an aerobic inner layer and an anaerobic outer layer. Thus, aerobic bacteria, e.g., iron-oxidizing bacteria (IOB) and sulfur-oxidizing bacteria (SOB), as well as anaerobic bacteria, e.g., iron-reducing bacteria (IRB) and sulfate-reducing bacteria (SRB), are favored in the inner layer and outer layer of the rhizoplane biofilm, respectively. In the inner layer, ferrous sulfide is oxidized by IOB and SOB to Fe〈sup〉3+〈/sup〉 and SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉. Fe〈sup〉3+〈/sup〉 is thereafter bound with oxygen into iron (hydro)oxides, aggregating into a barrier of iron plaque for heavy metal sequestration and O〈sub〉2〈/sub〉 diffusion. Excessive SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉 diffused to the outer layer is reduced to S〈sup〉2−〈/sup〉 by SRB, forming sufficient metal sulfide precipitates that on one hand immobilize those heavy metal ions released by H〈sup〉+〈/sup〉, and on the other hand serve as a barrier for preventing the contact of ferrous sulfide from O〈sub〉2〈/sub〉. Hence, further oxidization of ferrous sulfide is terminated.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This rhizoplane biofilm co-existing with IP contributes to the rhizosphere element circulation. Further investigation and demonstration of its composition, structure, and function will help us better interpret the survival strategy and bioremediation potential of wetland plants in flooded mining areas, such as mine tailing ponds in tropical and sub-tropical regions with abundant rainfall.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉We conducted this project to develop a feasible method for mapping tropical peat lands of Bengkalis Island—as a test site—in Indonesia.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The method based on limited availability of field measurements and a wide range of remotely sensed spatial datasets like radar elevation product, MODIS, and Landsat imageries. We applied land use category based sampling to extend existing field data of peat thickness. New peat thickness data was collected by boring and simultaneous electrical resistivity tomography (ERT). Based on remotely sensed and field data sets, peat maps were compiled by simulated spatial annealing. Peat map statistics were derived after 500 runs including mean, median, minimum, maximum, and percentile values.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The resulted maps represent the limiting values of expected peat thickness using 90% confidence level. Results showed that ERT is suitable for determining peat layer thickness. Using independent samples, we found that peat thickness predictions tend to overestimate peat thickness by ca. 2 m in general.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉According to predictions, the peat volume of Bengkalis Island is estimated to be in the range of 3.28–3.58 km〈sup〉3〈/sup〉.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The field capacity (FC) and permanent wilting point (PWP) are important soil hydraulic properties that determine the maximum available water for plants, and they are crucial parameters for biophysical models and irrigation management. However, previous estimates of the FC and PWP failed to consider their spatial correlations at the regional scale. Therefore, we estimated the FC and PWP using the state-space equation by considering the spatial correlations between soil properties.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉We estimated the FC and PWP using a first order autoregressive state-space equation based on the elevation (Elev), bulk density (BD), soil texture (Clay, Silt, Sand), soil organic carbon (SOC), and land use (LU) with a data set obtained from 104 in situ sampling sites across the entire Hexi Corridor.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results indicated that the distributions of the FC and PWP exhibited moderate variations in the Hexi Corridor, with values of 0.127 ± 0.060 and 0.075 ± 0.034 g/g (mean ± 1 standard deviation (SD)), respectively. According to 〈em〉t〈/em〉 tests, the autocorrelation coefficients for FC, PWP, Elev, LU, Silt, Sand, and SOC as well as the cross-correlation coefficients between FC, PWP, and pertinent variables were significant with one lag distance (approximately 40 km) (〈em〉p〈/em〉 ˂ 0.05). Calculations of the coefficient of determination (〈em〉R〈/em〉〈sup〉2〈/sup〉) and root mean square error (RMSE) showed that the state-space models performed better at estimating FC and PWP than multiple linear stepwise regression models (SMLRs). Bivariate state-space equations based on Silt and LU were the optimal models for estimating FC (〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.999, RMSE = 0.002 g/g) and PWP (〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.997, RMSE = 0.002 g/g). According to the coefficients in the optimal state-space models, soil texture and LU were the dominant factors that affected the spatial variability in FC and PWP. After neglecting the spatial correlations between variables, the SMLRs showed that BD and soil texture were the best variables for estimating FC and PWP.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The state-space approach is recommended as a useful tool for quantifying larger-scale spatial patterns in soil properties.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The purpose of this study was to compare effects of two biostimulating substances (compost and bird droppings) on the proliferation of microorganisms, enzymatic activity, and resistance of spring barley in soil exposed to tebuconazole fungicide. Both biostimulating substances were also assessed for their efficacy in tebuconazole degradation in soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A pot vegetation experiment was performed with soil belonging to the Eutric Cambisols to test the effect of tebuconazole on the biological activity of soil. Its adverse effect on the biological properties of soil was minimized through the use of biostimulating substances (compost and bird droppings), the effect of which was expressed with the IF〈sub〉C/BD〈/sub〉 index. The 〈em〉RCh〈/em〉 index was used to determine the effect of tebuconazole on the proliferation of soil microorganisms and enzymes, the BA〈sub〉21〈/sub〉 index was used to express soil fertility based on the activity of soil enzymes, whereas the RS index—to express the resistance of spring barley to the administered doses of tebuconazole. Finally, analyses were conducted to determine the efficacy of soil amendment with biostimulating substances in tebuconazole degradation.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Study results demonstrate that tebuconazole caused significant changes in the proliferation of the tested groups of microorganisms, in the activity of soil enzymes, and in spring barley yield. It was especially noticeable in pots in which the soil was exposed to its highest dose, i.e., 2.499 mg kg〈sup〉−1〈/sup〉. Soil supplementation with bird droppings had a positive effect on the development of soil microorganisms and on the enzymatic activity in the soil. In turn, compost addition to soil exerted various effects on the biological properties of soil. Both biostimulating substances failed to improve spring barley yield. Tebuconazole degradation was more intense in the soil fertilized with bird droppings than with compost.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Results of this study suggest that tebuconazole can affect the stability and health status of soil ecosystems by modifying their biological properties. The high sensitivity of soil microorganisms and enzymes to stress conditions makes them reliable environmental bioindicators. The strive for eliminating the adverse impact of fungicides on soil microbiome through the use of appropriate remediation methods, like, e.g., biostimulation, is of greater concern from the ecological perspective.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Mining areas are low-quality habitats for macro- and microorganisms’ development, mainly due to the degradation of the soil quality by metal pollution. The present work aimed to analyze the influence of metal contamination and of plant species on the rhizospheric microbial communities of four indigenous metallophytes (〈em〉Ononis natrix〈/em〉, 〈em〉Haloxylon scoparium, Peganum harmala〈/em〉, and 〈em〉Aizoon canariense〈/em〉) growing along a metal contamination gradient in Kettara mine near Marrakech, Morocco.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉In pyrrhotite mining areas (Kettara mine, Morocco), rhizosphere soil samples were collected from four predominant indigenous metallophytes (〈em〉O. natrix〈/em〉, 〈em〉H. scoparium〈/em〉, 〈em〉P. harmala〈/em〉, and 〈em〉A. canariense〈/em〉) growing along a metal contamination gradient (ZC, control zone; Z1, high metal contamination; Z2, moderate metal contamination; Z3, low metal contamination). Microbial communities were analyzed by using microbial counts and by denaturing gradient gel electrophoresis (DGGE). The physicochemical properties (pH, conductivity, total organic carbon, nitrogen, P Olsen, and metal concentrations) of soils were also determined.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The physicochemical analysis revealed that rhizospheric soils from Z1, Z2, and Z3 were relatively poor in nutrients as they presented low levels of total organic carbon and nitrogen, organic matter and available P. Moreover, these rhizospheric soils showed high concentrations of metals, especially Cu and Pb, which significantly reduced the abundance of the different groups of soil microorganisms (bacteria, fungi, and actinomycetes) and the activity of soil dehydrogenase. The analysis of bacterial communities by DGGE revealed that bacterial diversity was not negatively affected by metal contamination being higher in the most contaminated area (Z1).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Overall, the microbial abundance, the composition, and the diversity of rhizospheric bacterial communities were more influenced by the environmental factors in sampling zones than by plant cover. Microbial counts and enzymatic activity were both systematically affected throughout the metal gradient, evidencing as good indicators of the harmful effects of anthropogenic disturbances in soils. 〈em〉H. scorparium〈/em〉 and 〈em〉P. harmala〈/em〉 proved to be good candidates for the development of phytotechnological programs aiming the revegetation of mining degraded areas.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Climate changes have significant impacts on crop yield, and also on crop quality related to food safety and human health. This study investigated the influences of atmospheric carbon dioxide (CO〈sub〉2〈/sub〉) enrichment on cereal metal accumulation in soil-crop system.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Field rotation experiments of rice (〈em〉Oryza sativa〈/em〉) and winter wheat (〈em〉Triticum aestivum〈/em〉) were conducted by simulating elevated CO〈sub〉2〈/sub〉 concentrations (e[CO〈sub〉2〈/sub〉]) in 12 open-top chambers (OTCs). The treatments included the ambient [CO〈sub〉2〈/sub〉] (CK), 80 ppm (T1) and 200 ppm (T2) above ambient condition, respectively. Different parts of above-ground plant samples were analyzed for metal concentrations (Cu, Zn, Fe, Mn; Ca, Mg) at the key growth stages, assisted with analyses of soil pH, metal bioavailability, and transfer factors (TFs).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The result patterns were opposite for rice and wheat. After the increased transport from rhizospheric soil solution due to the metal mobilization by declined pH, most metals increased their distributions in rice grain, husk, and stem than leaf. While for winter wheat, though soil metal bioavailability was also increased, their distributions in grain, husk, and stem were decreased owing to possible carbohydrate dilution effect or cation competition, except some macro metals distributed more in leaf.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Since results of metals and crops are not always consistent among various reports, the mechanisms of essential/toxic metal transport in soil-crop system affected by climate change and its impacts on human health deserve further studies.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Elevated CO〈sub〉2〈/sub〉 and nitrogen (N) addition both affect soil microbial communities, which significantly influence soil processes and plant growth. Here, we evaluated the combined effects of elevated CO〈sub〉2〈/sub〉 and N addition on the soil–microbe–plant system of the Chinese Loess Plateau.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A pot cultivation experiment with two CO〈sub〉2〈/sub〉 treatment levels (400 and 800 μmol mol〈sup〉−1〈/sup〉) and three N addition levels (0, 2.5, and 5 g N m〈sup〉−2〈/sup〉 year〈sup〉−1〈/sup〉) was conducted in climate-controlled chambers to evaluate the effects of elevated CO〈sub〉2〈/sub〉 and N addition on microbial community structure in the rhizosphere of 〈em〉Bothriochloa ischaemum〈/em〉 using phospholipid fatty acid (PLFA) profiles and associated soil and plant properties. Structural equation modeling (SEM) was used to identify the direct and indirect effects of the experimental treatments on the structure of microbial communities.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Elevated CO〈sub〉2〈/sub〉 and N addition both increased total and fungal PLFAs. N addition alone increased bacterial, Gram-positive, and Gram-negative PLFAs. However, elevated CO〈sub〉2〈/sub〉 interacting with N addition had no significant effects on the microbial community. The SEM indicated that N addition directly affected the soil microbial community structure. Elevated CO〈sub〉2〈/sub〉 and N addition both indirectly affected the microbial communities by affecting plant and soil variables. N addition exerted a stronger total effect than elevated CO〈sub〉2〈/sub〉.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The results highlighted the importance of comprehensively studying soil–microbe–plant systems to deeply reveal how characteristics of terrestrial ecosystems may respond under global change.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉This study aimed to investigate the benefits of retaining harvest residues on the dynamics of soil C and N pools following clear-cut harvesting of a slash pine plantation in South East Queensland of subtropical Australia.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Immediately following clear-cut harvesting, macro-plots (10 × 10 m) were established on a section of the plantation in a randomised complete block design with four blocks and three treatments: (1) residue removal (RR〈sub〉0〈/sub〉), (2) single level of residue retention (RR〈sub〉1〈/sub〉) and (3) double level of residue retention (RR〈sub〉2〈/sub〉). Soils were sampled at 0, 6, 12, 18 and 24 months following clear-cutting and analysed for total C and N, microbial biomass C (MBC) and N (MBN), hot water–extractable organic C (HWEOC), hot water–extractable organic N (HWEON), NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉–N and NO〈sub〉〈em〉x〈/em〉〈/sub〉〈sup〉−〈/sup〉–N.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The study showed that although soil total C decreased in the first 12 months following clear-cutting, harvest residue retention increased soil total C and N by 45% (〈em〉p〈/em〉 〈 0.001) and 32% (〈em〉p〈/em〉 〈 0.001), respectively, over the 12–24 months. NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉–N, HWEOC, HWEON and MBC showed initial surges in the first 6 months irrespective of residue management, which declined after the 6th month. However, residue retention significantly increased HWEOC and HWEON over the 12–24 months (〈em〉p〈/em〉 〈 0.001).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study demonstrated that harvest residue retention during the inter-rotation period can minimise large changes in C and nutrient pools, and can even increase soil C and nutrient pools for the next plantation rotation.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Rapid industrialization in China accelerated environmental pollution by xenophores and trace metals particularly cadmium. Numerous studies have been conducted to address soil contamination using organic and inorganic amendments under pot or incubation conditions, but few were performed under field conditions, particularly in the wheat-growing areas. This study aims to investigate the effectiveness of pre-applied soil amendments for Cd immobilization, changes in soil pH, and metal uptake by wheat.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉In this study, 12 treatments, i.e., control (CK), lime, DaSan Yuan (DASY), DiKang No. 1 (DEK1), biochar, Fe-biochar, Yirang, CaMgP, and green stabilizing agents (GSA-1, GSA-2, GSA-3, and GSA-4), were evaluated for Cd immobilization in incubation and field experiments. Changes in soil pH and available metal content with amendments were monitored from 30 to 150 days of incubation. Single extraction method and DTPA-extractable and sequential extraction procedures were employed to assess the variations in available Cd contents of field soil. The impact of soil amendments on Cd uptake and bioaccumulation in food part of wheat was measured at harvesting stage in a contaminated site.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Lime treatment increased soil pH by 32% and reduced available Cd to 0.213 mg kg〈sup〉−1〈/sup〉, as compared to CK (control) in the incubation experiment (0.343 mg kg〈sup〉−1〈/sup〉). Effects of the amendments on wheat growth, soil pH, and Cd phytoavailability were reported. Wheat biomass was highest in treatment GSA-2 (13,880 kg ha〈sup〉−1〈/sup〉) and GAS-4 resulted in an increase in grain yield (5350 kg ha〈sup〉−1〈/sup〉). Soil pH of the treated field at harvesting stage increased up to 6.50, 6.50, and 6.47 by application of GSA-4, GSA-2, and lime, respectively. Cadmium contents in wheat grain were declined significantly in the treatments of GSA-2, GSA-4, and lime.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Results of this study revealed a significant decrease in available Cd concentration with the application of amendments. Composite amendments were more effective in terms of metal uptake and bioaccumulation in wheat. In addition, our results indicate the effectiveness of composite amendments in stabilizing Cd in contaminated soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Acid rain events in Yuebei, a region of northern Guangdong Province, China, have been increasing due to rapid urbanization in recent years. A three-year study was conducted to assess the effect of rainfall on losses of dissolved calcium (Ca〈sup〉2+〈/sup〉) from limestone soils in a karst area in Yuebei.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soil leachate was collected from 61 events that produced more than 100 ml leachate per event during a 3-year period.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Each rainfall event caused on average a loss of 8.5 × 10〈sup〉−4〈/sup〉 g Ca〈sup〉2+〈/sup〉 kg〈sup〉−1〈/sup〉 soil with a Ca〈sup〉2+〈/sup〉 loss of 2.16 × 10〈sup〉−5〈/sup〉 g kg〈sup〉−1〈/sup〉 per mm of rain. Cumulative net Ca〈sup〉2+〈/sup〉 loss from the soil for the 61 events monitored was 0.05 g kg〈sup〉−1〈/sup〉. In terms of Ca-loss per mm rain, the largest net Ca〈sup〉2+〈/sup〉 loss from the soil occurred with mild acid rain (pH 4.5–5.6), followed by non-acid rain (pH 5.6–6.29) and severe acid rain (pH 〈 4.5). Net Ca〈sup〉2+〈/sup〉 losses through natural rainfall were significantly larger than those induced by simulated rainfall with distilled water (control) or rainwater from the karst depression area of an adjacent talus slope. Total water soluble Ca〈sup〉2+〈/sup〉 content in the soil continuously decreased due to acid rain, with a total reduction of 0.36 g kg〈sup〉−1〈/sup〉 during the three-year experimental period. Net Ca〈sup〉2+〈/sup〉 losses from the soil were positively correlated with leachate Ca〈sup〉2+〈/sup〉 concentration and rainfall and negatively correlated with rainwater pH.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The losses of Ca〈sup〉2+〈/sup〉 from the soil can increase the risk of acidifying soils in the flat karst area in Yuebei, which may also affect the adjacent regions through changing the chemistry of groundwater and surface water.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Collapsing gully erosion is a specific form of soil erosion that is widely distributed in the hilly granitic region of tropical and subtropical southern China and resulted in extremely rapid water and soil loss. The aim of this study was to investigate the correlations between soil physicochemical and shear properties and the clay mineralogical of different profiles of the non-eroded soils (without soil erosion) and collapsing gully soils in Changting County, Fujian Province, southeastern China.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A total of 32 sampling soils collected from four pedons of non-eroded and collapsing gully soils were subjected to conventional soil analyses for physicochemical properties. The soil shear strength of collected soils was measured using a triaxial shear apparatus according to the unconsolidated-undrained (UU) method. The clay mineralogical of different profiles soils was examined with an X-ray diffraction (XRD) analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that non-eroded soils had superior physicochemical characteristics. The cohesive force of the non-eroded soils was generally greater than that of collapsing gully soils. The XRD patterns of the clay fraction indicated that kaolinite, illite, hydroxy-interlayered vermiculite (HIV), and gibbsite were the dominant clay minerals in the studied soils. Pearson’s correlation analysis showed that the cohesive force of the studied soils had significant and positive correlations with CEC, exchangeable Al〈sup〉3+〈/sup〉 + H〈sup〉+〈/sup〉, Fe〈sub〉d〈/sub〉, Al〈sub〉d〈/sub〉, and Fe〈sub〉t〈/sub〉; the correlation coefficients (〈em〉R〈/em〉 value) for cohesive force were greater than those of internal friction angle. The stepwise multiple linear regression analyses indicated that exchangeable Al〈sup〉3+〈/sup〉 + H〈sup〉+〈/sup〉 and Al〈sub〉d〈/sub〉 were the dominant factors affecting cohesive force.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Compared with collapsing gully soils, non-eroded soils had superior physicochemical and shear properties, indicating that non-eroded soils were better able to resist soil erosion. The findings obtained in the present study were of fundamental significance in understanding the correlation between shear strength and the soil physicochemical properties in the non-eroded soils and collapsing gully soils of tropical and subtropical China.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The effect of organic matter on the As bioavailability in soils and thus on phytoremediation processes is still controversial. The objective of the present study was to evaluate the combined effect of compost and microorganisms from rhizosphere on the tolerance of barley and wheat plants to soil polluted with different concentrations of As for the application on phytoremediation strategies.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A greenhouse experiment was performed using soil artificially contaminated with As at two doses. A compost obtained from sewage sludge composted with pruning waste was used (40 t/ha) as amendment. Plants were grown until the end of their growing cycle. Arsenic uptake and plant physiological and biochemical parameters as well as As availability and physicochemical properties in soil samples were analyzed. The impact of compost addition on the structure and diversity of the microbial communities of the rhizosphere was also evaluated using PCR-DGGE.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Compost application induced a different behavior in both species. Compared to wheat and irrespective of As doses, in compost amended soils, barley plants showed an enhanced As translocation to the aerial part. The different bacterial communities structure found for each species, according to the PCR-DGGE cluster analysis, suggested that specific rhizobacteria of barley may have increased As bioavailability, and would therefore enhance its translocation to aerial parts.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Both species could be used for phytoremediation proposes of As-polluted soils, and specifically, barley would be an interesting option for phytoextraction due to its higher biomass and high As translocation when compost is applied to As-polluted soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Urbanization is an important process that changes land use pattern and the sustainability of agroecosystems in the urban-rural transition zone. Through intensified anthropogenic activity, urbanization magnifies trace element (TE) inputs into soils and alters the balance of soil element fluxes. This study aims to investigate the effects of urbanization on the spatial dynamics of soil HMs in peri-urban zones and the distinct behaviors of TEs in response to urban sprawl.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉An area (15 km × 16 km) in the Chinese northeastern black soil region was selected to represent a typical urban-rural transition feature that received heavy impact by urbanization in last decade. Two hundred topsoil samples were taken from locations dominated by Phaeozem soils and analyzed for total Zn, Cu, As, Pb, Cd, Cr, Ni, and Hg. Principal component analysis (PCA) was used to distinguish the probable sources of TE inputs into the soils. The overall TE pollution of soils was evaluated by the Nemerow comprehensive pollution index. Inverse distance weighting algorithm combined with autocorrelation analysis was used to analyze the spatial patterns of soil TE distribution.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The mean concentrations of the studied TEs, with the exception of Hg and As, were higher than their background values, and their concentrations were always higher in the part closer to the urbanized area. Soil pollution assessment shows that the overall pollution status was moderate, but for Cd and Cu, numerous hotspots were identified due to the overuse of agrochemicals. PCA showed that Cu, Zn, Pb, and Cd as the first component were due to urbanization and agronomic practices, whereas As, Ni, and Cr as a second group were primarily of lithogenic origin, partly due to urbanization, and Hg was related to the atmospheric deposition of industrial waste gas.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Increasing urban sprawl in the study area resulted in higher TE concentrations in the southern part of the region than the northern part, confirming the positive effect of urbanization on excessive soil TE accumulation. Although the pollution status was not yet serious, with the current rate of urban growth, arable soils in the peri-urban area will continuously be contaminated and control measures must be taken to prevent the cumulative impact on human health.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Stream sediment can control phosphorus (P) in the water column at baseflow. Two common laboratory analyses of sediment P are the equilibrium phosphate concentration at net zero sorption (EPC〈sub〉0〈/sub〉) and P fractionation. Good sample handling ensures representative results, but oftentimes, studies rely on air-dried or freeze-dried samples, which alters sediment biogeochemistry. How and to what extent this influences EPC〈sub〉0〈/sub〉 and P fractionation remains unclear. We therefore examine pretreatment effects on sediment EPC〈sub〉0〈/sub〉 and P fractionation.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉We collected fine sediments (〈 2 mm) from streams in the Tukituki River and Reporoa Basins in New Zealand (〈em〉n〈/em〉 = 31 sediments). Subsamples were then either kept fresh, frozen then lyophilized (freeze-dried), or dried at 40 °C for 2 weeks (air-dried). Measurements of EPC〈sub〉0〈/sub〉 and P fractionation were made in triplicate. The sequential P fractionation scheme determined five different P pools: NH〈sub〉4〈/sub〉Cl (labile P), NaOH reactive P (RP; metal oxide-bound P) and unreactive P (URP; organic P), HCl (Ca-mineral P), and residual P. Along with statistical comparisons between fresh results and the two pre-treatments, we explored correlations between pre-treatment effects and sediment physicochemical characteristics.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The sediments had generally low EPC〈sub〉0〈/sub〉 (majority 〈 0.020 mg P L〈sup〉−1〈/sup〉), and uncertainty in EPC〈sub〉0〈/sub〉 increased with concentration magnitude. While there were sediment-specific changes in EPC〈sub〉0〈/sub〉 with pre-treatment, there was no consistent bias caused by pre-treatment. However, the differences between the fresh and air-dried sediment EPC〈sub〉0〈/sub〉 were larger and more variable than between fresh and freeze-dried sediment. For P fractionation, the Tukituki sediments were enriched in HCl-P, while Reporoa sediments had more NaOH-RP and NaOH-URP. Despite large sediment-specific changes, the overall effects of freeze- and air-drying sediment were increased NH〈sub〉4〈/sub〉Cl-P (estimated average effect, 〈span〉 〈span〉\( \widehat{\theta} \)〈/span〉 〈/span〉 = + 0.63 and + 3.7 mg P kg〈sup〉−1〈/sup〉), no significant changes for NaOH-RP, contrasting changes in NaOH-URP (− 3.4 and + 3.3 mg P kg〈sup〉−1〈/sup〉), and decreased HCl-P (− 40 and − 33 mg P kg〈sup〉−1〈/sup〉).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We found that drying sediment significantly influenced EPC〈sub〉0〈/sub〉 and P fractions (especially the NH〈sub〉4〈/sub〉Cl-P fraction). Air-drying was particularly error-prone and should be avoided. The use of freeze-drying to preserve samples for later analyses and improve ease of handling may be used with appropriate consideration of the research objectives and the error introduced by freeze-drying. However, we recommend using fresh sediments for analyses whenever possible, as they best represent natural conditions.〈/p〉 〈/span〉

Description: 〈p〉This article has been retracted by the Editors-in-Chief.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The research aimed to determine the transport velocities of aniline (AN) and nitrobenzene (NB) in sandy sediment so as to predict the pollution plume in sandy aquifer. The transport velocities of organic compounds in aquifer depend on various factors. This research also evaluated the effects of compound type, single or mixture solute systems, pore-water velocity (〈em〉v〈/em〉), and pH on the transport velocities of AN and NB. These results will facilitate more precise determination of transport velocities.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Column experiments containing sorption and desorption periods were conducted using typical sandy sediment from JiangHan Plain, China. Special emphasis was placed on the variation of compounds, solute systems, 〈em〉v〈/em〉 from 4.5 to 10 cm h〈sup〉−1〈/sup〉, and pH from 5 to 8.5. The transport curves of AN and NB were simulated using different sorption models coupled in HYDRUS-1D and the partition coefficient, 〈em〉K〈/em〉〈sub〉d〈/sub〉, was determined by inverse solution. The retardation coefficient (〈em〉R〈/em〉) and transport velocity (1/〈em〉R〈/em〉) were calculated based on 〈em〉K〈/em〉〈sub〉d〈/sub〉 and the basic properties of the column. The transport velocities of AN and NB in various experimental conditions were compared and discussed.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The linear non-equilibrium two-site (L2Site) sorption model coupled in HYDRUS-1D best described the sorption of AN and NB during the transport process in the sandy sediment. The 1/〈em〉R〈/em〉 values of AN and NB were 0.47–0.67 m and 0.16–0.21 m, respectively. AN transported three times faster than NB in both single and mixture systems. Lower 〈em〉v〈/em〉 enhanced the transport of AN but displayed limited impact on the transport of NB in single solute system. In mixture solute system, the 1/〈em〉R〈/em〉 values of AN tended to decrease and NB increase at lower 〈em〉v〈/em〉, which suggested an interference between AN and NB transports. Both transport velocities of AN and NB potentially increase with pH.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉AN and NB can transport 0.47–0.67 m and 0.16–0.21 m, respectively, when groundwater flows 1 m at various experimental conditions. The transport velocities of AN and NB depend on the type of compounds, single or mixture solute system, 〈em〉v〈/em〉, and pH. All the factors should be considered when we determine the parameter, transport velocities, for prediction of pollution plume.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Amendment of animal manures into eroded soils is an important approach to improving nutrient status and increasing the concentration of soil organic carbon (SOC). However, the contribution of the manure carbon to SOC and its variation along soil profile has not been quantified.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉We simulated soil erosion in a mollisol by removing the top soils of 0-, 5-, 10-, 20-, and 30-cm depth and compared SOC in soil profiles 10 years after either chemical fertilization alone or combined with cattle manure application.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Increasing erosion depth decreased SOC concentration and weakened soil aggregation. Compared to the chemical fertilization only, the addition of cattle manure significantly increased SOC accumulation and soil aggregation, which mainly occurred in 0–40-cm depths. The greatest effect of manure application was observed in the 10-cm erosion treatment. The application of cattle manure increased the 〈sup〉13〈/sup〉C abundance in aggregates and bulk soil in the top 40 cm of soil profile. Using the natural 〈sup〉13〈/sup〉C abundance method, we quantified the contribution of the cattle manure to SOC at 0–40-cm depths ranging from 1.1 to 8.4% across erosion treatments.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The greatest contribution of the manure-C to SOC occurred in surface layer with 10 cm of soil removal. The application of animal manures was recommended for restoring severely eroded soils.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Metallic nanomaterials (MNM) like cobalt oxide (〈em〉nano〈/em〉-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) are currently attracting enormous interest owing to their unique size and shape-dependent properties and potential applications in various sectors. The aims of this study were to assess the toxicity of 〈em〉nano〈/em〉-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and to propose a risk limit through the estimation of a Predicted No Effect Concentration (PNEC) for this MNM to soil biota.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉For this purpose, a battery of sub-lethal ecotoxicological tests was performed to assess the influence of this MNM on four plant species (endpoints: germination and growth) and two invertebrate species (endpoints: avoidance and reproduction) following standard protocols. Further, biochemical endpoints (acetylcholinesterase [AChE], catalase [CAT], glutathione-S-transferase [GST] activity, and lipid peroxidation [LPO]) were also assessed in 〈em〉Eisenia andrei〈/em〉, one of the invertebrate species tested, in order to contribute for refining the PNEC value.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The recorded data showed a significant inhibition in the germination of 〈em〉L. lycopersicum〈/em〉 and in the growth of 〈em〉Z. mays〈/em〉, even at the lowest concentration tested (269.3 mg kg〈sup〉−1〈/sup〉 soil〈sub〉dw〈/sub〉 of 〈em〉nano-〈/em〉Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉). Concerning the soil invertebrates, the results showed only significant avoidance (〈em〉p〈/em〉 〈 0.05) by 〈em〉E. andrei〈/em〉 in the soil contaminated with the highest concentration tested (1000 mg kg〈sup〉−1〈/sup〉 soil〈sub〉dw〈/sub〉 of 〈em〉nano-〈/em〉Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉), while no significant ecotoxicological effect on reproductive outputs of both species was recorded. However, the data reported for AChE, CAT, GST, and LPO showed significant effects at the range of concentrations tested in 〈em〉E. andrei〈/em〉. Thus, we recorded, the occurrence of oxidative stress and the enhancement of lipid peroxidation, on this invertebrate species.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The data obtained in this study supports the proposal of a PNEC value of 9.1 mg kg〈sup〉−1〈/sup〉 soil〈sub〉dw〈/sub〉 for 〈em〉nano-〈/em〉Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 in soil. The integration of data from biochemical endpoints allowed the refinement of the PNEC value and to obtain a more protective threshold.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Sex effects may cause significant changes in rhizosphere microbial community composition and soil properties. Although dioecious plants are widespread, little is known about rhizosphere microenvironmental differences in response to dioecious plants.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉This study characterized microbial species by next-generation sequencing and evaluation of soil properties in the rhizosphere of male and female 〈em〉Populus cathayana〈/em〉 plants located in non-saline area (control site), salt lakeside (low salt), salt mountain (middle salt), and salt factory (high salt) areas.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉A total of 5 phyla, 18 classes, 57 orders, 108 families, and 211 genera of fungi were observed in the rhizosphere of 〈em〉P. cathayana〈/em〉, while 18 phyla, 35 classes, 69 orders, 149 families, and 329 genera of bacteria were observed in the rhizosphere of 〈em〉P. cathayana〈/em〉. With increasing salinization, the microbial community diversity in the rhizosphere of 〈em〉P. cathayana〈/em〉 first increased and then decreased, especially in the fungal community. Site and sex had significant effects on microbial communities and caused adjustments in microbial community structure. Redundancy analysis (RDA) showed that available K, ammonium nitrogen (NH4-N), and nitrate nitrogen (NO3-N) as well as Na〈sup〉+〈/sup〉 and Cl〈sup〉−〈/sup〉 contents and the electrical conductivity (EC) were the main factors affecting the microbial community in the rhizosphere of 〈em〉P. cathayana〈/em〉 in the Chaka Salt Lake ecosystem.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This is the first study focusing on microbial communities and soil properties in the rhizosphere of male and female 〈em〉P. cathayana〈/em〉 plants with different degrees of salinity. In addition, potential differences in the preferences of the microbial communities between the two sexes exist.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Rhizosphere and fertilization might affect soil microbial activities, biomass, and community. This study aimed to evaluate the impacts of 〈em〉Phyllostachys edulis〈/em〉 (moso bamboo) rhizospheres on soil nutrient contents and microbial properties in a moso bamboo forest with different fertilizer applications and to link soil microbial activities with abiotic and biotic factors.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The experiment included three treatments: (1) application of 45% slag fertilizer (45%-SF); (2) application of special compound fertilizer for bamboos (SCF); and (3) the control without any fertilizer application (CK). Simultaneously, bulk soils and 0.5, 2.5, 4.5, and 6.5-year-old (y) bamboo rhizosphere soils were selected. Soil nutrient contents were analyzed. Microbial activities were evaluated based on the activities of soil enzymes including β-glucosidase, urease, protease, phosphatase, and catalase. The total microbial biomass and community were assessed with the phospholipid fatty acids (PLFAs) method.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉In the CK and SCF treatments, organic matter contents of rhizosphere soils were significantly higher than those of bulk soils. Soil β-glucosidase, urease, protease, phosphatase, and catalase activities in rhizosphere soils were higher than those of bulk soils, with the sole exception of β-glucosidase of 0.5 y rhizosphere soil in the 45%-SF treatment. Compared with the CK treatment, fertilizer applications tended to increase soil total PLFAs contents and changed soil microbial community. Moso bamboo rhizospheres did not significantly increase the total microbial biomass. In the SCF treatment, the Shannon index of bulk soil was significantly lower than those of rhizosphere soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our results suggested that both rhizospheres and fertilizer applications could change the soil microbial community structures and that moso bamboo rhizosphere could increase microbial activity rather than biomass in the forest soils with different fertilizer applications.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Pyrolysis is the most effective method to completely remove antibiotics and immobilize heavy metals from livestock feces. However, the effect of the pyrolysis temperature on antibiotic removal at laboratory and pilot scales is still unclear.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The pyrolysis technique was used to convert pig manure (PM) and chicken manure (CM) into biochar at different temperatures from 300 to 700 °C in a laboratory-scale test. The performance of antibiotic removal and heavy metal immobilization in livestock feces was studied, and the optimal temperature of 600 °C was selected for the pilot-scale verification.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that the removal of the antibiotics tylosin (TYL), tetracycline (TC), chlortetracycline (CTC), doxycycline (DOXY), sulfamethazine (SMZ), sulfadiazine (SDZ), and sulfamethoxazole (SMX) was satisfactory, and all seven typical antibiotics were completely removed at 600 °C. In addition, the heavy metals zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd), and arsenic (As) in the manure were well immobilized, and higher temperatures (above 600 °C) favored their immobilization. The results of heavy metal immobilization and antibiotic removal of the pilot-scale test were similar to those of the laboratory-scale test.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Laboratory- and pilot-scale experiments showed that the current study provided a safe method and technology for treating and recycling livestock feces into biochar via the pyrolysis process.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Serious soil salinization, including excessive exchangeable sodium and high pH, significantly decreases land productivity. Reducing salinity and preventing alkalization in saline-sodic soils by comprehensive improvement practices are urgently required. The combinations of aluminum sulfate with different types of fertilizer at different rates were applied on rice paddy with saline-sodic soils of the Songnen Plain in Northeast China to improve soil quality and its future utilization.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Experiments were carried out in a completely randomized block design. Twelve treatments with aluminum sulfate at the rates of 0, 250, 500, and 750 kg hm〈sup〉−2〈/sup〉 with inorganic, bio-organic, and organic-inorganic compound fertilizers were performed. Soil pH, electronic conductivity (EC), cation exchangeable capacity (CEC), exchangeable sodium percentage (ESP), total alkalinity, sodium adsorption ratio (SAR), soil organic carbon (SOC), available nutrients, soluble ions, rice growth, and yield in the saline-sodic soils were measured across all treatments. The relationships among the measured soil attributes were determined using one-way analysis of variance, correlation analysis, and systematic cluster analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The pH, EC, ESP, total alkalinity, SAR, Na〈sup〉+〈/sup〉, CO〈sub〉3〈/sub〉〈sup〉2−〈/sup〉, and HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 in saline-sodic soil were significantly decreased, while CEC, SOC, available nitrogen (AN), available phosphorus (AP), available potassium (AK), K〈sup〉+〈/sup〉, and SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉 were significantly increased due to the combined application of aluminum sulfate with fertilizer compared with the fertilizer alone. The most effective treatment in reducing salinity and preventing alkalization was aluminum sulfate at a rate of 500 kg hm〈sup〉−2〈/sup〉 with organic-inorganic compound fertilizer. This treatment significantly decreased the soil pH, EC, ESP, total alkalinity, SAR, Na〈sup〉+〈/sup〉, and HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 by 5.3%, 28.9%, 41.1%, 39.3%, 22.4%, 23.5%, and 35.9%, but increased CEC, SOC, AN, AP, AK, K〈sup〉+〈/sup〉, SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉, rice height, seed setting rate, 1000-grain weight, and yield by 77.5%, 115.5%, 106.3%, 47.1%, 43.3%, 200%, 40%, 6.2%, 43.9%, 20.3%, and 42.2%, respectively, compared with CK treatment in the leaching layer.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The combined application by aluminum sulfate at a rate of 500 kg hm〈sup〉−2〈/sup〉 with organic-inorganic compound fertilizer is an effective amendment of saline-sodic soils in Songnen Plain, Northeast China. These results are likely related to the leaching of Na〈sup〉+〈/sup〉 from the soil leaching layer to the salt accumulation layer and desalination in the surface soil, and the increase of SOC improved the colloidal properties and increased fertilizer retention in soil. In addition, the environmental impact of aluminum sulfate applied to soil needs to be further studied.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The concentrations and distribution of arsenic (As) in two different soil types (Vertisols and Entisols) of Central Mexico impacted by mine activities and irrigation with As-rich groundwater are analyzed in order to determine their impact on the soil quality, and to contribute reliable data that may help to assess the environmental risk that represents the progressive accumulation of As in the arable soils of Guanajuato.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Two Entisol and two Vertisol profiles located in the Guanajuato state (Mexico) were described and sampled from ~ 1.20-m-deep pits. Soils are irrigated with As-rich deep and shallow groundwaters that were sampled from irrigation boreholes. Additionally, a Vertisol profile located in a parcel not impacted by irrigation was sampled and used as a control soil. Minerals were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with dispersive X-ray spectrometry (EDS). Geoaccumulation indexes (Igeo) were calculated to evaluate As enrichment with respect to a control soil and the Upper Continental Crust (UCC). Anions and cations of groundwater were analyzed by high-performance liquid chromatography (HPLC) and by inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. As in soils was determined by ICP-AES.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Near total As concentrations are higher in Entisols (mean As value = 7.20 mg/kg) than in Vertisols (mean As = 1.02 mg/kg). As concentrations in the control soil are lower (0.34 to 0.70 mg/kg). The in-depth distribution of As in Vertisol profiles reveals that the higher As concentrations are found in the uppermost horizons (10 cm) and they tend to decrease with depth. In Entisols, As concentrations do not follow a vertical trend. Igeo values of As indicate moderate to heavy As contamination in Vertisols and moderate contamination in Entisols. SEM-EDS analyses revealed the presence of some potential As-bearing minerals such as magnetite and abundant Fe oxides and Ti-Fe coatings precipitated onto feldspar grains, particularly in Entisols.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Irrigation of Vertisols with As-rich groundwater determines As concentrations in the uppermost horizons that exceed the natural background of the region (0.4 mg/kg). In depth, clay grain-sized particles inhibit the downward migration of As, while Fe oxides and organic matter scavenge As by adsorption. As concentrations in Entisols are higher, and the in-depth distribution of this element is controlled by periodic contributions of As-bearing minerals delivered from mine prospects located at the river’s catchments.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Suspended matter (SM) in streams is usually considered of minor importance in Danish environmental management. However, SM has some ecological effects as it may (1) clog fish spawning grounds and (2) act as an important agent for transport and exposure of biota to chemical substances, such as phosphorus and toxic inorganic (e.g. heavy metals) and organic (e.g. pesticides) substances.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A large national data set of 〉 100,000 water samples analysed for SM and loss on ignition was investigated for spatial concentration patterns, sediment yields and temporal trends. Moreover, the importance of SM as a transport agent for phosphorus and heavy metals in streams was investigated through a correlation analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The mean suspended matter concentration (SMC) (including organic matter) amounted to 12 mg l〈sup〉−1〈/sup〉, with an organic content of 4.9 mg l〈sup〉−1〈/sup〉 (41%). A clear difference in SMC temporal trends over the sampling period was found between geographical regions. Sediment yields were calculated for all major catchments revealing low sediment yields (1–15 t km〈sup〉−2〈/sup〉 year〈sup〉−1〈/sup〉) compared to neighbouring countries and showed clear geographical patterns. Statistically significant relationships were established between SMCs, suspended sediment concentrations (SSCs) (excluding organic matter) and organic matter concentrations (OMCs) and particulate phosphorus (PP) concentrations, and again spatial patterns appeared. However, it was clearly shown that SMC/SSC/OMC could not be used as a robust, nationwide, indicator for PP concentrations. Analyses of the relationship between SMC and particle-bound heavy metal concentrations generally revealed weak correlations except for Pb and Ni (median 〈em〉R〈/em〉〈sup〉2〈/sup〉 〉 0.3).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Relatively low SM concentrations and sediment yields were found. SM is, in some geographical regions, an important transport agent for PP. Clear geographical patterns occurred in the relationships between SMC/SSC/OMC and both river water discharge and PP, as well as for sediment yields and for temporal trends in SMC.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Moss covers a vast area from the polar to the tropics on a global scale and has important regulatory effects on the biogeochemical processes in the soil. Previous studies had shown that moss on soil could reduce soil temperature in the warm period and plays an important role in the stability of the soil carbon pool in the context of global warming. The cooling effect of soil temperature by moss may be due to its ability to accelerate soil water evaporation. Most vascular plants achieve limited homeothermy by transpiration, but moss has no organs which can regulate transpiration. Can moss also regulate soil water evaporation as the transpiration of vascular plants? The objective of this study was to determine the differences in temperature and evaporation between moss-covered and bare soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A year-round mesocosm experiment was carried out to investigate soil temperature and evaporation with and without moss. We used a high time-resolution instrument which could simultaneously monitor soil temperature beneath moss layers, photosynthetically active radiation, and near-surface air temperature (20 cm above the soil) in a 10-min interval. In the meantime, we used a chamber method to monitor soil evaporation and heat flux inside the mesocosms simultaneously.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉We found that the evaporation of the moss increased drastically when near-surface air temperature exceeded 30 °C, which kept maximum soil temperature around 30 °C. This finding was different from many previous studies which reported that the evaporation of moss was always greater than bare soil or similar to open water surface. The phenomenon we found may be important for moss, which allowed moss to minimize the loss of water at high temperature and maintain a relatively constant temperature. It is known that moss is a C〈sub〉3〈/sub〉 plant, and the high-temperature threshold for the photosynthesis of C〈sub〉3〈/sub〉 vascular plants is also around 30 °C. Thus, the temperature-regulating behavior could improve the net carbon gain for moss and benefit for its survival. To our best knowledge, there is no research reporting this phenomenon. In the context of global warming, the temperature-regulating behavior of moss is very important for its controls on soil carbon dynamics and its other ecological functions, especially at lower latitudes with higher soil temperature.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our result showed that moss can also achieve limited homeothermy through soil water evaporation similarly as the vascular plant through transpiration, and the temperature threshold was around 30 °C. This homeothermy led to the decoupling of soil temperature and near-surface air temperature. How mosses elevate water evaporation in response to high temperature remains to be a challenge for future research.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Although wetlands are one of the major ecosystems on the earth, information about the bacterial communities in different types of wetlands, especially in northeast China, has not yet been fully described. The aim of this study was to compare bacterial community compositions between sediment and water in different types of wetlands of northeast China.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉In this study, sediment and water samples were synchronously collected from different types of wetlands in northeast China. The bacterial communities were analyzed with Illumina MiSeq sequencing targeting the 16S rRNA gene.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that the dominant phyla (relative abundance 〉 5%) across all sediment samples were 〈em〉Proteobacteria〈/em〉 and 〈em〉Chloroflexi〈/em〉, while those across all water samples were 〈em〉Proteobacteria〈/em〉, 〈em〉Actinobacteria〈/em〉, and 〈em〉Bacteroidetes〈/em〉. Bacterial community composition was distinctly different among wetlands at the phylum and genus levels, and the indicator species for different sediment and water samples also varied greatly. The alpha diversity of bacterial community was higher in sediment samples than in water samples, and the lowest alpha diversity was detected in two coastal wetlands, both in sediment and in water samples. A heatmap analysis at the genus level and principal coordinate analysis revealed that all bacterial communities in sediment or in water samples were separated into distinct groups according to wetland type, and the communities in two coastal wetlands were highly similar to each other both in sediment and water samples, respectively. Bacterial communities in sediment were mainly affected by the available K content, followed by total C and total N, soil pH, etc., while in water, the communities were mainly affected by total P, total K, etc.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The results revealed that bacterial community compositions between sediment and water samples were significantly different, and the communities in two coastal wetlands were more similar than those in other wetlands. The wetland sediment samples demonstrated higher community alpha diversity than the water samples, and alpha diversity was lowest in both the sediment and water of two coastal wetlands. Moreover, bacterial communities in sediment and water were driven by different environmental factors.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Biochar has shown to be a great product to control the bioavailability of potentially hazardous elements (PHE) in contaminated soils. Despite the advantages associated with the application of biochar in agricultural soils, relatively few studies have focused on the effects of biochar amendments on soil chemical properties, accumulation of arsenic, cadmium, zinc, and lead in rice tissues, and their availability in soil systems.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The field experiment was conducted at the paddy soils in Hunan Province, China. The soil texture was sandy clay loam. Wheat-derived biochar was applied once to the experimental plots at the rates of 0, 10, 20, 30 and 40 t ha〈sup〉−1〈/sup〉, and referenced as A0, A10, A20, A30, and A40, respectively. For PHE determination, soil samples and plant samples were digested with a mixed solution of HCl:HNO〈sub〉3〈/sub〉 (4:1, 〈em〉V〈/em〉:〈em〉V〈/em〉) and HCl:HClO〈sub〉4〈/sub〉 (4:1, 〈em〉V〈/em〉:〈em〉V〈/em〉), respectively, and the arsenic, cadmium, zinc, and lead in the digest solution were measured by ICP-MS (Thermo Fisher Scientific, USA). The soil available fraction of PHE (arsenic, cadmium, zinc, and lead) was extracted by diethylenetriamine pentaacetic acid (DTPA) and measured by inductively ICP-MS.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Biochar amendment increased chemical properties of soil organic matter, pH, electrical conductivity, cation exchange capacity, nitrate nitrogen, and available phosphorus. Soil DTPA extractable arsenic, cadmium, zinc, and lead concentrations were significantly reduced. Arsenic, cadmium, zinc, and lead in rice shoots, and arsenic, cadmium, and zinc in roots significantly decreased after amendment. Concentrations in rice tissues positively and negatively correlated with the soil available fraction of PHE and soil chemical properties, respectively. Soil electrical conductivity negatively correlated with the soil available fraction of PHE. Concentrations of arsenic, zinc, cadmium, and lead in rice roots declined relative to increases of cation exchange capacity (arsenic, zinc), available phosphorus (cadmium), and nitric nitrogen (lead) content. Similar relationships were observed between cation exchange capacity and PHE in shoots.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Biochar creates avoidance of PHE through regulating chemical properties through biochar sorption capacity. Cation exchange capacity, available phosphorus, and nitric nitrogen were the principle factors affecting roots uptake of arsenic, zinc, cadmium, and lead. Biochar soluble salts could decline availability of metals/metalloids in soils through precipitation. Wheat-derived biochar application is an alternative safe product to immobilize PHE in rice paddy soils by restricting the risk of PHE.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The purposes of this paper are to investigate the geochemical characteristics of rare earth elements (REEs) in the surface sediments of Jiulong River, southeast China, to probe the provenance compositions of the sediments, and to analyze the potential anthropogenic influence on REEs in the sediments. REEs and Sr-Nd isotopes were selected as the tools because REEs can be used to identify the anthropogenic effects on sediments and Sr-Nd isotopes have been widely known as powerful tracers for provenance analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Fifty-three samples of surface sediments (0~5 cm) were collected from Jiulong River. The concentrations of REEs and Sr-Nd isotopic compositions in the surface sediments were determined by inductively coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS), respectively. The chondrite-normalized and WRAS-normalized REEs patterns, enrichment factor, plots of La-Th-Sc and La/Yb-∑REE, and plots of ε〈sub〉Nd(0)〈/sub〉 vs 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr and ε〈sub〉Nd(0)〈/sub〉 vs δEu are presented.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The mean concentration of ΣREEs in the surface sediments of Jiulong River was 254.25 mg kg〈sup〉−1〈/sup〉. The mean values of ΣLREEs (227.6 mg kg〈sup〉−1〈/sup〉), ΣHREEs (26.64 mg kg〈sup〉−1〈/sup〉), and (La/Yb)〈sub〉N〈/sub〉 ratios (9.24) suggested an enrichment of LREEs compared to HREEs. Negative Eu anomalies were observed in the surface sediments. The distribution patterns of REEs in the surface sediments from different areas of Jiulong River were remarkably similar. The values of 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr, 〈sup〉143〈/sup〉Nd/〈sup〉144〈/sup〉Nd, and ε〈sub〉Nd(0)〈/sub〉 were 0.714091~0.733476, 0.511875~0.512271, and − 14.88~− 7.16, respectively. The plots of ε〈sub〉Nd(0)〈/sub〉 vs 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr, ε〈sub〉Nd(0)〈/sub〉 vs 1/[Nd], and ε〈sub〉Nd(0)〈/sub〉 vs δEu indicated that the sediments in Jiulong River were mainly derived from natural geological processes and the REEs might be also influenced by anthropogenic activities such as Fujian Pb-Zn deposit, coal ash, and industrial sludge.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The REEs in the surface sediments at different sites are similar in geochemical characteristics, with a right-inclined distribution pattern and higher enrichment of light REEs (LREEs) compared to heavy REEs (HREEs), and a negative Eu anomaly but no evidence of Ce anomaly. The sediments in Jiulong River were mainly derived from natural geological processes (granite and magmatic rocks), and the REEs in the sediments were also influenced by anthropogenic activities (Fujian Pb-Zn deposit, coal ash, and industrial sludge).〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The addition of maize residue nitrogen (N) to the soil strongly influences soil N accumulations, but the specific contributions of maize residue N to soil aggregates based on long-term fertilization remain largely unknown. This study involved a 360-day laboratory incubation experiment to determine the dynamics of N derived from maize straw in Mollisol soil aggregates applying different long-term fertilization treatments.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉In 2015, three soil samples from different fertilizers treatments were collected from the upper layer of soil (0–20 cm) of the field at a long-term Mollisol (〈em〉Luvic Phaeozem〈/em〉) experimental site established in 1980 in Gongzhuling, Jilin Province, China. The fertilizer treatments included no fertilizer (CK); a combination of nitrogen, phosphorous and potassium fertilizers (NPK); and NPK combined with manure (MNPK). Three treatments of soils were incubated for 360 days at 25 °C, with or without 〈sup〉15〈/sup〉N-labeled maize straw and destructively collected on days 45, 90, 135, 180 and 360. Soil samplings were separated into two aggregate fractions (macroaggregates, ≥ 0.25 mm; microaggregates, 〈 0.25 mm) using the wet sieving method.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The higher amounts of maize straw–derived N were incorporated into the macroaggregate on day 90 in the three treatments (average of 65.4%) and into the microaggregate in the MNPK (11.5%), NPK (9.5%), and CK (6.7%) treatments on days 360, 360, and 45, respectively. The maize straw–derived N remaining in the soil aggregates (macroaggregate and microaggregate) was in the order of NPKM 〉 NPK 〉 CK after 360 days of incubation.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The results revealed that the combined application of chemical fertilizer and organic manure had higher capacity to retain maize straw–derived N, and more of it was retained in macroaggregates in the beginning. The addition of straw residue accelerated the formation of macroaggregates in the soils with lower C/N ratios.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of the research was to determine the potential of dissolved humic substances extracted from leonardite to mobilize Cu and Pb from multi-metal contaminated soils with the scope of finding an efficient washing solution as a possible substitute for conventional washing agents used to extract heavy metals from polluted soils around mining areas.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The efficiency of dissolved humic substances extracted from leonardite to extract Cu and Pb from multi-metal contaminated soil collected from “Larga de Sus” mine (Romania) was determined under batch conditions by single-step extraction. All extraction experiments were conducted in a stirrer with orbital rotation-oscillation and thermostat cupola at 100 oscillations/min and oscillation amplitude of 32 mm. The influence of stirring time (120, 240, 360, 720, 1440, 2400 min), concentration of humic solution (2% and 5%), and soil:solution ratio (mass:volume (m/V)) of 1:8, 1:10, and 1:16 on the Cu and Pb removal efficiency was investigated. The heavy metal concentration from soil and extractant solution was determined through atomic absorption spectrometry.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The Cu and Pb removal process from soil using dissolved humic substances proceeded relatively quickly. In investigated experimental conditions, the best Cu and Pb removal efficiencies were observed after 360 min of stirring when 60.3% of Cu and 48% of Pb were extracted from soil (2% humic washing solution). The removal efficiency of Cu increased with increasing the soil:solution ratio and humic solution concentration, at shorter stirring times. In the case of Pb, an important improvement of the mobilization with an increasing soil:solution ratio or humic solution concentration was not observed, along with investigated stirring time. A soil:solution ratio of 1:8 was sufficient to reduce the Cu concentration in the studied soil below the intervention threshold established by Romanian legislation, after 360 min of stirring.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The mobilization of Cu and Pb from multi-metal contaminated soil using dissolved humic substances is strongly dependent on stirring time, soil:solution ratio, and concentration of humic washing solution. Nevertheless, the results of the present study demonstrate that dissolved humic substances extracted from leonardite are fairly effective washing agents for soils polluted with Cu, Pb, multiple heavy metals, and other pollutants in high concentrations.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Soil aggregates play a crucial role in the sequestration of soil organic carbon (SOC). Returning crop residues to soil is known to strongly influence soil C stocks, but the specific contribution of crop residues to soil aggregates influenced by long-term fertilization remains largely unknown. This study investigated the effects of long-term fertilization on the distribution of 〈sup〉13〈/sup〉C-labeled maize straw residue in different aggregate size fractions and their retention in soils over a 1-year incubation.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The dynamic variation and the distribution of maize straw-derived 〈sup〉13〈/sup〉C in soil aggregates were monitored using a 〈sup〉13〈/sup〉C stable isotope mass-balance approach. The following three fertilization treatments were selected: (1) without fertilization (CK), (2) mineral fertilizer (NPK), and (3) cow manure with mineral fertilizer (NPKM). Soil samples were collected from the surface layer (0–20 cm) of a long-term field experiment of Mollisols (〈em〉Luvic Phaeozem〈/em〉) in 2015 at Gongzhuling, Jilin Province, China, which was established in 1980. Soils were incubated for 360 days at 25 °C, with or without 〈sup〉13〈/sup〉C-labeled maize straw and destructively collected on the days of 45, 90, 135, 180, and 360. Soil aggregates were separated into two fractions (macroaggregates, 〉 250 μm; microaggregate, 〈 250 μm) by wet sieving.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The NPK treatment retained the most of maize straw 〈sup〉13〈/sup〉C in macroaggregates (28.49%), but more maize straw 〈sup〉13〈/sup〉C was incorporated in microaggregates for NPKM soil (4.02%) than NPK and CK on day 45. The highest amount of maize straw 〈sup〉13〈/sup〉C was incorporated in macroaggregate on the days of 90, 135, and 180, and in microaggregate on the days of 135, 45, and 135 for CK, NPK, and NPKM, respectively. Organic manure-amended soil tended to sequester more maize straw 〈sup〉13〈/sup〉C in the microaggregate fractions as compared with the NPK and CK treatments throughout the incubation. The maize straw 〈sup〉13〈/sup〉C remaining in both of macro- and microaggregates followed the order of NPKM 〉 NPK 〉 CK for all soil aggregates after the 360-day incubation.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our results illustrated that long-term application of manure with mineral fertilizer helps to stabilize or increase the retention of exogenous C in the soil aggregates.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Molecular markers in environmental geochemistry include natural product or pollutant chemicals in sediments that are indicative of discharge sources or emission pathways. Four classes of molecular marker compounds, including fatty acids, sterols, PCBs, and PAHs, in surficial sediments (top 2 cm) collected along a downstream transect of the Potomac River within the US mid-Atlantic region were analyzed and correlated with potential pollution discharge sources in close proximity to the sampling sites.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Thirty-five surficial sediment samples were collected using a petite Ponar grab sampler along a 320-km longitudinal transect of the Potomac River (mid-Atlantic USA), a major tributary of Chesapeake Bay, ranging from the upland fluvial river to its confluence with the Bay. The sediments were collected along the transect at approximately equidistant points. The marker chemicals were extracted from sediments using microwave-assisted extraction and quantified on a dry weight basis by gas chromatography or gas chromatography-mass spectrometry. Sediment moisture, texture, and organic carbon and nitrogen content were also determined.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Fatty acids and sterols were well correlated with ecological factors in the Potomac River, while the sterol ratio epi+brassicasterol/stigmasterol showed moderate spatial correlation with nearby waste treatment plants (WTPs) and city locations, especially in the upland and tidal freshwater river. The fecal sterol coprostanol also showed moderate spatial correlation with some WTPs in both the upland and tidal river. PCB and PAH concentrations were primarily correlated with urban and large military installations. PCBs in sediments appeared to be predominantly derived from Aroclors while PAHs showed a strong pyrogenic origin. Retene and perylene were unique markers for PAHs in sediment and were indicative of aged organic matter in sediments.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The marker chemicals had utility in identifying pollution emission sources and pathways in the Potomac River. For PCB pollutants, sediment profiles reflected localized source emissions from industrial sites. PAHs showed a downstream plume effect derived from urban Washington, DC. Fatty acids and sterols were most useful for identifying ecological shifts (i.e., terrestrial versus aquatic origin), but showed spatial correlations with wastewater treatment plants and cities.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Deep soil moisture has been considered to be critical for plant survival in water-limited ecosystems. The limited precipitation on the semi-arid Loess Plateau is the only water source for soil moisture and is unevenly distributed throughout the year. Characterizing the seasonal changes in deep soil moisture in relation to land use types and structures is important for the sustainability of vegetation restoration in this region.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A total of 27 experimental sites along seven transects were selected in the Jiegou catchment on the semi-arid Loess Plateau. These sites were covered by five land use types: native grassland, traditional farmland, abandoned farmland, and 5-year and 7-year 〈em〉Robinia pseudoacacia〈/em〉 (RP) forestlands. Soil moisture measurements were conducted during three seasons (spring, summer, and fall) at soil depths of 0 to 5 m in 0.2-m increments, and 2025 disturbed soil samples were collected to determine the gravimetric soil moisture content using the oven-dry method (24 h at 105 °C). The depth-averaged soil moisture was compared among different seasons and land use types using one-way ANOVA and significance tests.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Among the seasons, the depth-averaged soil moisture had the following order: fall 〉 spring 〉 summer. In the shallow layers (above 2 m), soil moisture in summer was significantly lower than that in spring and fall (〈em〉p〈/em〉 〈 0.05). The vertical distribution characteristics of soil moisture (0–5 m) were similar among the land use types during each season but different among the seasons for each land use type. In general, the depth-averaged values of soil moisture among the land use types were on the order of native grassland 〉 farmland 〉 forestland. This finding indicated that afforestation drastically decreased deep soil moisture, particularly in summer. Furthermore, the different land use structures significantly influenced the spatial distribution of deep soil moisture during each season.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study highlights the seasonal changes in both shallow and deep soil moisture under various land use types, which provides insights into the sustainable use of deep soil moisture and rational land use management on the semi-arid Loess Plateau of China.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of this meta-analysis was to investigate the interactive effects of environmental and managerial factors on soil pH and crop yield related to liming across different cropping systems on a global scale.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉This study examined the effects of liming rate, lime application method, and liming material type on various soil chemical properties and crop yield based on data collected from 175 published studies worldwide since 1980.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The most important variables that drive changes in soil pH and crop yield were liming rate and crop species, respectively. Soil conditions, such as initial soil organic matter and soil pH, were more important for increasing soil pH in field-based experiments, while lime material type and application method were more important for improving crop yield. To effectively neutralize soil acidity, the optimum liming duration, rate, and material type were 〈 3 years, 3–6 Mg ha〈sup〉−1〈/sup〉, and Ca (OH)〈sub〉2〈/sub〉, respectively. Averaged across different crop species, the application of CaO, CaCO〈sub〉3〈/sub〉, Ca (OH)〈sub〉2〈/sub〉, and CaMg (CO〈sub〉3〈/sub〉)〈sub〉2〈/sub〉 increased yield by 13.2, 34.3, 29.2, and 66.5%, respectively.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This meta-analysis will help design liming management strategies to ameliorate soil acidity and thus improve crop yield in agroecosystems.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉This study aims to investigate the combined rhamnolipid and saponin enhancing metals removal from the sludge.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The combined rhamnolipid and saponin was used to enhance metals removal from sludge in the multiple washing steps.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉High content of metals in the sludge led to the obstacle of sludge land application and nutrients recycling. The combined rhamnolipid and saponin enhancing metal removal from sludge was investigated in this study. Results indicated that metals removal efficiencies increased with mass ratio raising. After the multiple washing steps, Cu, Zn, Cr, Pb, Ni, and Mn removal efficiencies were 62%, 74%, 60%, 15%, 68%, and 64%, respectively. Meanwhile, metals fractions variations indicated that Pb exchangeable fraction, Mn reducible and oxidizable fractions, and Cu residual fraction obtained the highest removal efficiencies. Metal binding intensity increased, and metal mobility order was Zn 〉 Cr = Cu 〉 Ni = Pb 〉 Mn after the multiple washing steps. Preservation of fertilizing characteristics demonstrated that sludge would still be suitable for beneficial use in agriculture.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Combined rhamnolipid and saponin could be a replacement for inorganic, organic acids and less environmentally friendly refractory chelators. Copper, Zn, Cr, Ni, and Mn obtained better removal efficiencies than removal efficiency of Pb (15%), which were 62%, 74%, 60%, 68%, and 64%, respectively.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Biochar is one of the most widely used ameliorants for soil amendment, which is known as factor which rises crop yields and levels of soil biological activity. Nowadays, it is under investigated how biochar application affects the dynamics of the humic components and whole soil organic matter (SOM) and the processes of its alteration. This investigation is aimed to evaluate the influence of biochar on the content, composition, and transformation of humic acids (HAs) as the main component of the SOM.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The incubation experiment was carried out on three Podzol Antric soils, with varying amounts of initial total organic carbon. The incubation time was 90 days, using biochar gravimetric doses of 0.1 and 1.0%. The biochar was produced by fast pyrolysis of birch and aspen wood at 550 °С. Humus composition was analyzed for the organic matter fractions extracted with 0.1 M NaOH (containing HAs 1 + fulvic acids (FAs) 1) and 0.1 M Na〈sub〉4〈/sub〉P〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 (containing HAs 1 + FAs 1 + HAs 2 + FAs 2). Isolated HAs were characterized for their elemental composition (C, N, H, and S) and molecular composition with the use of solid-state 13C nuclear magnetic resonance (13C-NMR) techniques.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉We found that 0.1% of biochar amendment does not influence SOM mineralization, but 1.0% of biochar increases the mineralization by 15–18%. This process is accompanied by changes in the composition and properties of the HS. The increased proportion of HA aromatic fragments in biochar indicates an increasing of their stability. However, in soils with high humus content and a significant amount of insoluble matter, the processes of mineralization and the growth of HAs are taking place simultaneously. The replenishment of HAs could be the outcome of both the intensification of the transformation processes (mineralization and humification) of the more sustainable insoluble matter compounds and the humification of the biochar itself.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The influence of biochar on humification in Podzol Antric soils was revealed on the basis of incubation experiment. Both negative and positive changes under biochar in HS system were demonstrated. The active decrease of humus total contents and also the labile HS ought to qualify as negative changes. The increase of HA chemical maturity that leads to the stability of humus in whole as well as the intensive new HA formation thought to qualify as positive changes.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The bio-mitigation of acetochlor and improvement of fertility in soil using 〈em〉Rhodopseudomonas capsulata (R. capsulata)〈/em〉 in effluent was investigated in this research.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Acetochlor content and cytochrome P450 monooxygenase activity were tested using the HPLC method. 〈em〉EthB〈/em〉 gene regulation was measured by RT-PCR.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉It was observed that acetochlor was not degraded under the control group. The addition of effluent containing 〈em〉R. capsulata〈/em〉 and residual organics degraded acetochlor efficiently and re-mediated soil fertility. Acetochlor mitigation reached 100% after 5 days under the optimal group (2000 mg/L). Interestingly, the acetochlor began to be degraded after day 1 of inoculation. Further research indicated that 〈em〉EthB〈/em〉 gene was expressed after the first day of inoculation. Subsequently, the cytochrome P450 monooxygenase was synthesized to degrade acetochlor under 〈em〉EthB〈/em〉 gene regulation. Analysis revealed that 〈em〉EthB〈/em〉 and cytochrome P450 monooxygenase were inducible gene expressions and enzyme. The acetochlor as stimulus signal induced 〈em〉EthB〈/em〉 expression through signal transduction pathway. This process took 1 day for 〈em〉R. capsulata〈/em〉, as they were ancient bacteria. However, the organics in soil and the control group were deficient, which could not maintain 〈em〉R. capsulata〈/em〉 growth for over 1 day. The residual organics in effluent provided sufficient carbon sources and energy for 〈em〉R. capsulata〈/em〉 under four effluent groups.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The new method completed the remediation of acetochlor pollution and the improvement of soil fertility and soybean processing wastewater treatment simultaneously, as well as realizing the resource reutilization of wastewater and 〈em〉R. capsulata〈/em〉 as sludge.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The concentration and spatial distribution of many potentially toxic elements (PTEs) have not been studied in the mining areas of tropical soils in the Amazon. The objective of this study was to evaluate the concentrations and spatial distribution of Al, Bi, Fe, Li, Sn, Sr, Te, Ti, and V in an area influenced by artisanal gold (Au) mining and chemical attributes related to soil fertility.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The study area is located in Serra Pelada, on the east bank of the Brazilian Amazon, in the state of Pará. A total of 104 soil samples were collected with different forms of use: residential areas, agricultural, forest, and mining areas. 0.5 g of soil previously sieved at 0.15 mm was weighed to determine the pseudo total contents of the PTEs. The soil was mixed to 9 mL of concentrated 〈em〉HNO〈/em〉〈sub〉〈em〉3〈/em〉〈/sub〉 and to 3 mL of concentrated HCl; then, this solution was digested in microwave according to the EPA method 3051A (Test Methods for Evaluating Solid Waste 1–30, 2007). The digested extracts were filtered on blue filter paper and diluted with ultrapure water to the final volume of 50 mL. The pseudo total contents of Al, Bi, Fe, Li, Sn, Sr, Te, Ti, and V were determined by inductively coupled plasma optical emission spectrometry (ICP-OES).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The pseudo total concentrations of Al, Bi, Fe, Li, Sn, Sr, Te, Ti, and V were high, considering the natural occurrence in the soils. The levels of Li, Sn, Sr, Te, and V did not differ between them as forms of soil use, while the levels of Al, Bi, Fe, and Ti were higher in residential and/or agricultural areas. The spatial distribution maps of the elements showed that the material removed from the pit is not a major source of contamination. In the residential areas, the exploitation of the Au in the backyards provided greater surface accumulation. The accumulated geography index shown by Bi, Li, Sn, Sr, and Te varied from moderately contaminated to highly contaminated.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The pseudo total contents of the potentially toxic elements (PTEs) are high, characterizing a scenario of diffuse contamination and geoaccumulation of Bi, Li, Sn, Sr, and Te caused by anthropogenic activities. The mine pit opened during the initial exploration of the mine is not the only one contaminated by PTEs, the exploitation of tailings, backyards, and agricultural areas were other forms of environmental contamination.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Harbor sediments normally accumulate the pollutants from municipal and industrial activities in the estuarine zone. This work aimed to characterize the fractionation change of heavy metals in harbor sediments before and after chemical washing. Since the annual dredging around the Kaohsiung Harbor has increased over time, the influence of ex-situ acid washing on sediment quality needs to be evaluated.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Experimental parameters of acid washing included the solid loading (4–20%) and types (HCl, HNO〈sub〉3〈/sub〉, and citric acid) and concentrations (0.01–1 M) of acids. The fractionation of Cu, Zn, Ni, Cd, Cr, and Pb in the sediments at three estuaries, the Chienchen River, Canon River (Dock No.5), and Yanshui River, before and after washing processes were determined through sequential extraction.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The washing efficiencies of HCl, HNO〈sub〉3〈/sub〉, and citric acid were similar, being 80.1–83.7%, 27.6–30.9%, 20.7–23.9%, and 97.2–98.8% for Zn, Ni, Cr, and Cd, respectively. After 15 min of washing, HCl was found as a suitable washing agent, and particularly, more effective for Cu (65.3%) and Pb (79.4%) than other acids. The extraction process suggested that the acid washing of carbonate, the Fe-Mn oxide composite, and organic phases were highly correlated to their quantities in the sediments. However, the removal efficiency was inversely related to the metals in the residual phase.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Knowing the mobility and bioavailability of heavy metals based on fractionation of metals benefits the assessment of the potential risk of dredged harbor sediment after the washing procedure. This study provided evidence that acid washing, as a remediation method, could be versatile in removing heavy metals from mobile phases without causing mineralogical changes to the contaminated sediments of the harbor area.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Collapsing gullies, which involve considerable erosion and extreme landform changes, frequently occur in the granite region of Southern China. Capturing the evolution of collapsing gullies is useful and effective for predicting erosion amount and landform changes. However, the evolution of collapsing gullies is too complex to simulate using conventional models. The aim of this study is to modify the traditional cellular automata (CA)-Markov model for simulating the evolution of collapsing gullies and then quantify their morphology using landscape pattern metrics.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A hillslope eroded by collapsing gullies located in Longmen Town of the granite region of Southern China is used as a case study. Three digital elevation models (DEMs) were derived on 11 March 2017, 21 July 2017, and 2 December 2017 from a remotely piloted vehicle and global positioning system (GPS) real-time kinematics. Rainfall data for the corresponding time was recorded by a tipping-bucket rain gauge. Using these data, the CA-Markov model for simulating the evolution of collapsing gullies was developed, and then the most accurate one was chosen to predict the evolution on 2 December 2018. Evolution of the case study hillslope was interpreted and assessed using landscape metrics to capture the erosional trends of collapsing gullies.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The area differences of the modified CA-Markov model are lower than those of the traditional model while the kappa coefficients of the modified CA-Markov model are higher than those of the traditional model; that is, the modified CA-Markov model performs better for simulating and predicting the evolution of collapsing gullies. The kappa coefficients also demonstrate that both scouring and gravity impact collapsing gullies, and scouring force is more effective than gravity. Based on the evolution prediction, the erosion amount of collapsing gullies in the subsequent year is predicted to be 904.1 m〈sup〉3〈/sup〉. Spatial pattern analysis showed that the mid-lower part of a hillslope eroded by collapsing gullies will continue to be intensively eroded and the ground surface will become more fragmented.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The use of a modified CA-Markov model and landscape pattern metrics provide an improved and effective method for understanding the spatial and temporal variations of collapsing gullies landform and ground surface, as well as better capturing the erosional trends of collapsing gullies.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Phosphorus (P) in calcareous soil often needs to be replenished repeatedly. P-enriched biochar is expected to improve soil available P. However, the effect of acid biochar incorporated with other P activators on the P availability in calcareous soil is rarely reported.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉One soil incubation for 56 days was conducted to investigate the influence of individual application of acid biochar (B), phosphatase (E), 〈em〉Bacillus megaterium〈/em〉 (M), and their combined application (BE, BM, EM, BEM) on soil P availability, based on analysis of Olsen-P, water-soluble P, P forms, acid phosphomonoesterase (AcP), alkaline phosphomonoesterase (AlP) activity, and pH after 7, 14, 28, and 56 days of incubation.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Results indicated that individual application of B significantly increased soil Olsen-P and AcP compared with CK in the whole incubation period. Individual application of M significantly increased soil AcP and AlP on the 14th and 56th day of incubation, but decreased soil Olsen-P significantly in the whole incubation.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Individual application of B was the best measure for improving P availability in calcareous soil, followed by application of BM. But individual application of E or M was not recommended. Further investigations are required to investigate the influence of acid biochar on P availability in calcareous soil at the field scale.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Significant changes in the runoff and sediment load have been detected in many catchments of the Loess Plateau. These changes are expected to be influenced by the interplay of climate variability and human activities. Quantitatively evaluating these effects is crucial for framing climate variability adaptation measures and the assessment and management of regional water resources.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Based on the annual rainfall, runoff, and sediment load data taken over the period from 1974 to 2013 and using data from 112 flood events, this study investigates the runoff and sediment load variations at the annual scale and distinguishes the impacts of climate variability and human activities at the event scale. The Mann-Kendall test and Pettitt’s test are employed to detect the trends and abrupt change points of the annual runoff and sediment load. Rainfall and land surface conditions play a dominant role in the runoff and sediment yield of flood events. However, vegetation recovery, which benefits from the Grain-for-Green project and the construction of check dams has greatly changed the land surface condition, resulting in a reduction in streamflow energy, hydrological connectivity, and flood peaks. Therefore, for two flood events with similar rainfall conditions but different runoff and sediment yield, the differences in the runoff and sediment load within paired events may be attributed to the changes in the land surface condition induced by human activities.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that the annual runoff and sediment load has significantly decreasing trends (〈em〉p〈/em〉 〈 0.05). The abrupt changing point was detected in 1996, dividing the runoff and sediment load series into a baseline period (1974–1995) and a changing period (1996–2013). At the flood event scale, the hysteresis analysis showed that the counter-clockwise and figure-eight loops are the main patterns for both of the periods. The relationships between the runoff depth (〈em〉H〈/em〉) and sediment yield (SY) varied greatly in 2007–2013 compared with those during 1974–1989. Human activities accounted for an average of 47 and 81% for the changes in the runoff and sediment load, respectively, and the remainder was attributable to climate variability.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Human activities have a greater effect on the sediment load reduction in the Xichuan River catchment, while climate variability accounted for more of the runoff changes.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Dechlorane plus and its related compounds (DPs) are halogenated flame retardants. DP residues were widely detected in sediment because of its high hydrophobicity and extensive use in the electronics industry. In this study, Tenax extraction, a well-established method, was used to measure the effects of total organic carbon (TOC) content in sediment, aging time, and temperature on desorption behavior of DPs from sediment. Consequently, the bioavailability was estimated.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Three sediments (S1, S2, S3) with different TOC contents and particle-size distributions were collected from several different rivers and reservoirs in China. The sediments were spiked with a mix of DPs and extracted with Tenax resin. Desorption kinetics of DPs was obtained by measuring the amount of DPs that Tenax absorbed from sediments at 20 time points (1, 2, 3, 4, 6, 8, 10, 12, 24, 48, 72, 96, 144, 192, 240, 360, 480, 648, 816, or 1080 h). Then, the sediment (S1) with the highest TOC content was selected to study the effects of aging (14 days and 60 days) and temperature (30 °C and 50 °C).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Desorption kinetics were well described by a first-order three-compartment model. The content of TOC has different effects on the desorption of DPs. Desorption rates of dechlorane 602 (Dec 602) and Dec 604 decreased with the increase in TOC contents, while those of syn〈em〉-〈/em〉DP and anti-DP were the largest in S2, which has an intermediate TOC content. The desorption of Dec 603 in S1 and S2 were similar, which may be attributed to similar contents of clay and silt in those two sediments. With the decreasing temperature and increasing aging time, the rapid fractions (〈em〉F〈/em〉〈sub〉rap〈/sub〉) of DP, Dec 602, Dec 603, and Dec 604 decreased. The desorption of decachloropentacyclooctadecadiene (anti-Cl〈sub〉10〈/sub〉-DP) and undecachloropentacyclooctadecadiene (anti-Cl〈sub〉11〈/sub〉-DP) was unaffected by TOC contents, aging time, and temperature.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The contents of TOC have different effects on desorption of DPs. After aging, DPs release from sediment more slowly, and high temperatures will speed up this process. According to 〈em〉F〈/em〉〈sub〉rap〈/sub〉 and 〈em〉t〈/em〉〈sub〉99.9〈/sub〉 values, DP is a group of halogenated flame retardants with low bioavailability, and Dec 602 has the highest bioavailability for biota among DPs.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Gensburg Markham Prairie (GMP), a high-quality tallgrass prairie and wetland in the Chicago area, is surrounded by high-traffic highways and residential communities. Anthropogenic inputs are a concern given observed ecosystem degradation around the periphery of the prairie. To understand soil quality and the potential for habitat degradation in GMP, we evaluated concentrations of metals and phosphorus in soil profiles, identified possible sources of contamination, and assessed the likelihood that contamination would impact the prairie ecosystem.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉We collected 15 intact soil cores (to a depth of 120 cm) and 22 surface soil samples (0–10-cm depth), determined the soil type, and measured pH, organic matter, and concentrations of Pb, Cu, Zn, Mg, Fe, K, Ca, and P using ICP-OES. To quantify soil pollution, we calculated the element enrichment factor (EF) and single element pollution index (SEPI) for each sample. We also used principal component analysis (PCA) to interpret relationships between site variables, elemental concentrations, and sources of metals.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Heavy metals (Pb, Cu, and Zn) and P were found to accumulate in surface samples. The mean EF values for Pb, Cu, Zn, and P revealed significant enrichment of these elements in the soil profiles. However, SEPI analyses indicate that GMP soils have a low level of contamination. PCA revealed that concentrations are highest for samples with high organic matter content near the ground surface and that Pb, Cu, and Zn have common sources of pollution.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We observed enrichment of Pb, Cu, Zn, and P because of deposition from the urban built environment, but the enrichment levels are low enough that they are not expected to negatively impact the ecosystem of GMP. The detailed soil chemistry data constitute a spatial contamination map that can be used to assess potential long-term impacts on the ecosystem, such as reduction of plant growth and species diversity, and inform site management and biodiversity conservation efforts.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of this study was to screen plant species for remediation of oil-polluted soil in a semi-arid loess area.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Pot experiments were conducted to test six indigenous plant species: ryegrass (〈em〉Lolium perenne〈/em〉), tall fescue (〈em〉Festuca ovina〈/em〉), wheatgrass (〈em〉Agropyron cristatum〈/em〉), alfalfa (〈em〉Medicago sativa〈/em〉), erect milkvetch (〈em〉Astragalus adsurgens〈/em〉), and caragana (〈em〉Caragana korshinskii〈/em〉). Loessial soil was spiked with crude oil at five pollution levels (0, 0.5, 1, 2, and 4%, 〈em〉w〈/em〉/〈em〉w〈/em〉). We analyzed plant growth parameters at different stages, soil oxidoreductase activities, and oil degradation rate under different treatments.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Soil pollution by oil negatively affected the germination rate, plant height, and biomass of all six species while inhibiting soil dehydrogenase and catalase activities. These inhibitory effects increased with increasing oil pollution level, with 2% and 1% being the critical levels at which plant growth and soil oxidoreductase activities were significantly inhibited, respectively. Both oxidoreductase activities in the rhizosphere soil were significantly higher than those in the bulk soil, which led to a considerable increase in the degradation rate of total petroleum hydrocarbons (TPHs) in the rhizosphere. The plants showed varying remediation effects in the oil-polluted soil. Erect milkvetch and caragana showed potential for remediation of soil below the 0.5% pollution level, alfalfa for soil below the 1% pollution level, and ryegrass, tall fescue, and wheatgrass for soil below the 4% pollution level. The oil pollution level was negatively correlated with plant height, biomass, oxidoreductase activities, and TPH degradation rate for the six plants (〈em〉p〈/em〉 〈 0.01), whereas plant biomass was positively correlated with plant height and TPH degradation rate (〈em〉p〈/em〉 〈 0.01). Dehydrogenase activity was significantly positively correlated with catalase activity (〈em〉p〈/em〉 〈 0.01), while both of them were positively correlated with TPH degradation rate (〈em〉p〈/em〉 〈 0.05 and 〈em〉p〈/em〉 〈 0.01, respectively).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉In conclusion, the six indigenous plants exhibited different tolerances to oil pollution, among which ryegrass, tall fescue, and wheatgrass had the greatest potential for remediation of oil-polluted soil in the loess area.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The majority studies used the biochar or nanoparticles alone in metal-contaminated soils while less is known about the combined use of these amendments in metal-contaminated soils. We aimed to explore the efficiency of iron oxide nanoparticles (Fe NPs) and biochar on cadmium (Cd) uptake in rice in pot trial.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉An experiment was performed under ambient environmental conditions in a Cd-contaminated soil with and without biochar addition (1.0% 〈em〉w〈/em〉/〈em〉w〈/em〉), and different Fe NP concentrations (0, 10, 20, 30 mg/L) were foliar sprayed at different time intervals (at 3rd, 4th, and 5th weeks of nursery transplantation in the pots) during the plant growth. After harvesting, rice growth, photosynthesis, Cd and Fe contents in rice tissues, and soil bioavailable Cd and soil pH were measured.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Iron NPs enhanced the dry weights of rice tissues, chlorophyll concentrations, and gas exchange characteristics and the impact of NPs was further increased when the biochar was applied along with NPs. Iron NPs significantly decreased the intake of Cd in rice shoots by 31 and 42% and in rice roots by 26 and 39% with the foliar spray of Fe NPs (30 mg/L) without and with biochar, respectively. Foliar spray of Fe NPs reduced the total Cd accumulation by shoots, whereas the total Cd accumulation in the roots increased. The co-presence of Fe NPs and Cd enhanced the Fe concentrations in shoots of rice by 52 and 33% and in roots of rice by 32 and 21% when 30 mg/L Fe NPs were supplied with and without biochar, respectively. The effects of Fe NPs were higher with biochar application than without biochar except Fe concentrations in rice seedlings where the opposite trend was observed.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The increase in biomass, Fe concentrations in tissues, and decrease in Cd levels in plants clearly demonstrate that Fe NPs + biochar could be a promising technique for the utilization of Cd-contaminated soils in the future.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Microalgae, biochar, or organic manure (OM) can be used as soil amendments to enhance soil organic carbon (OC) content. In the present study, a mixture of all three was used to test whether they could further improve soil OC content and the soil’s ability to retain and fix carbon.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A laboratory incubation study was carried out to evaluate the efficacy of using microalgae, biochar, OM, or their mixture, as a soil amendment to improve OC in soil extract. Metabolic processes and soil microbial community structuring were analyzed to explore the mechanism by which the mixture increased the capacity of soil to act as a carbon sink.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉OC increased markedly (2.9 times its initial level) following the amendment of the soil with a treatment comprising microalgae, biochar, and the highest dose of OM. Microalgal metabolites were utilized by soil microorganisms as a carbon source. Biochar reduced the concentration of extracellular polysaccharides, whereas OM increased extracellular protein concentration. These metabolites affected the relative proportions of different groups of soil microorganisms, thereby increasing the proportion of 〈em〉Rhodobacter〈/em〉 and 〈em〉Runella〈/em〉, which exerted a positive synergistic effect on soil OC and increased the soil’s capacity to fix carbon.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉A mixture including microalga, biochar, and OM as a soil amendment improved the OC of soil extract, and its effect was greater than that of any of its components alone. The findings of this study can help in devising ways to increase the OC content and the CO〈sub〉2〈/sub〉-fixing capacity of the soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Soil salinization is a major restricting factor for crop growth and agriculture productivity in coastal areas. Exploring the evolution of soil salinization indicators and physicochemical properties and their relationships in a long-term scale can provide a basis for the restoration, utilization, and prediction of coastal salinized soil. This study aimed to investigate the impact of reclamation years on soil salinization indicators and physicochemical properties in reclaimed coastal tidal land, and analysis the linkage between soil salinization indicators and physicochemical properties after long-term reclamation.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soil sample sites were respectively collected from reclamation regions reclaimed in 1951, 1974, 1982, and 2007 according to typical land use types. Besides, the natural tidal flat was collected as control. Soil samples were divided into two parts to determine soil bulk density (BD), soil water content (SWC), soil particle size distribution (PSD), soil salt content (SSC), pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), organic matter (SOM), alkaline hydrolyzed nitrogen (AN), and available phosphorus (AP). One-way analysis of variations (ANOVA) was conducted to investigate the differences in soil properties within different reclamation years. The linkage between soil salinization indicators and soil physicochemical properties was analyzed by redundancy analysis and Monte Carlo permutation.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Compared with uncultivated tidal land, soil salinization indicators (SSC, pH, SAR, and ESP) significantly decreased after 30 years reclamation owing to the natural leaching and field management. Soil nutrients (SOM, TN, TP, AN, AP, CEC) apparently increased after reclamation of 30 years due to long-term fertilization. Moreover, SWC, BD, and SAND gradually decreased, whereas SILT and CLAY gradually increased after reclamation of 61 years. Soil salinization indicators were observed have a positive correlation with SAND and a negative correlation with SILT, CLAY, and soil nutrients.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Long-term reclamation could radically decreased soil salinization (SSC, pH, SAR, ESP) and apparently promoted soil nutrients accumulation (SOM, TN, TP, AN, AP, CEC). Furthermore, soil salinization indicators are closely related to soil physicochemical properties, and soil PSD and soil nutrients were considered as the key factors for the differences of soil salinization.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Information on root-zone soil water content (SWC) is essential for vegetation restoration, irrigation scheduling, and hydrological modeling. However, measurements of SWC within a variety of land uses may be time-consuming and labor-costing. This study tested whether SWC at a depth of a land use can be used to predict profile SWC of other land uses in terms of temporal stability analysis at a karst depression area in southwest China.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A total of 30 datasets of root-zone SWC from 0.1- to 0.5-m depths were collected by time domain reflectometry probes for three typical land uses from March 12 to November 8, 2015.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Results showed that the profile mean SWC and its associated standard deviation (SD〈sub〉P〈/sub〉) and coefficient of variation (CV〈sub〉P〈/sub〉) differed significantly (〈em〉P〈/em〉 〈 0.05) among the grassland, farmland, and forestland. The profile SWC was more temporally stable according to the apparently lower CV〈sub〉T〈/sub〉 in comparison with CV〈sub〉P〈/sub〉. The similarities of the vertical patterns of SWC were strong for the same land uses, while were relatively weak between the different land uses. The SWC measurements of the most temporally stable depth can be used to accurately predict profile SWC for both the same land use and other land uses.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study further expands the application of the temporal stability analysis and can aid water resource management in areas with diverse land uses.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Forest ecosystem acts as a significant sink and source of elements; however, the dynamics of trace elements (TEs) in soils of boreal zone are still poorly characterized. Data on relationships of TEs, major elements (MEs), soil properties, and parent rock geochemistry in boreal forest of Northeast Asia are scarce. Therefore, the objectives of this study were to evaluate the origination of TEs in forest soils and identify soil properties and ecosystem processes controlling accumulation and profile distribution of TEs.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Dystric Cambisols and underlying parent rocks have been sampled within hilly landscape covered by Gmelin larch (〈em〉Larix gmelinii〈/em〉 (〈em〉Rupr.〈/em〉) 〈em〉Rupr.〈/em〉) forests in Amur region (Russia). This paper considers 10-selected soil characteristics, total concentrations of 19 TEs, and 10 MEs measured by ICP-MS and RFA analysis. Factor analysis has been employed to highlight underlying relationships hidden in a complex data of element concentration and soil characteristics. Origination of TEs was assessed by using an enrichment factor (EF) considering concentration of TEs in soil in comparison to underlying parent rocks using Ti as a reference element.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉A group of biophile Zn, Mo, Sn, and Pb were enriched in the upper soil horizon, and depleted in mineral compared to parent rocks. Beryllium, Sc, Cr, Cu, Ga, Ge, Ta, Th, and U were depleted in both horizons. Ni and Cs show highest enrichment in both studied soil horizons. Frequently occurring forest fires affect soil characteristics and TEs dynamic only in the upper part of soil profile. Factor analysis revealed potential effect of exchangeable Na and soil pH on accumulation of the elements in the upper horizon, as a result of ash deposition by fire.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The studied TEs primarily originate from underlying parent rocks. Accumulation versus leaching of TEs in Dystric Cambisols might be element specific and affected by fire-derived ash. Our work shows that the upper horizon of forest soils could act as a significant sink of group of TEs. Therefore, long-term observations of TEs dynamic in soil profiles are needed to elucidate biogeochemical cycles in frequently burned forests of Northeast Asia. The present study for the first time has established an important wide data set of TEs concentration in Dystric Cambisols of natural boreal forests in the Russian Far East.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Calcareous soils are characterized by high pH and phosphorus (P) fixation capacity. Increasing application of P fertilizer recently has significantly improved soil P concentration, especially available P (Olsen-P) and inorganic phosphate (P〈sub〉i〈/sub〉) fractions. However, there are few data available on the ability of soils with different initial Olsen-P levels to continuously supply P (i.e., P desorption capacity) to crops without additional P fertilization and on which P〈sub〉i〈/sub〉 fraction exerts the greatest influence on P desorption capacity.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Five soils with different initial Olsen-P levels (0.5, 14.3, 38.4, 55.4, 72.3 mg kg〈sup〉−1〈/sup〉, hereafter refer as OP1, OP2, OP3, OP4, and OP5) but similar other soil properties were selected to evaluate the capacity of P desorption and its relationship with P〈sub〉i〈/sub〉 fractions. Soil P was sequentially extracted once daily for 16 consecutive days using Olsen solution.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The content and proportions of dicalcium phosphate fraction (Ca〈sub〉2〈/sub〉-P), octacalcium phosphate fraction (Ca〈sub〉8〈/sub〉-P), aluminum phosphorus fraction (Al-P), and iron phosphorus fraction (Fe-P) in P〈sub〉i〈/sub〉 increased significantly with the increase of initial Olsen-P (〈em〉P〈/em〉 〈 0.01). Applied P fertilizer was mostly stored as Ca〈sub〉8〈/sub〉-P in the soil. Soil P desorbed reached an equilibrium after 16 extractions for all soils, and P desorption capacity (12–358 mg kg〈sup〉−1〈/sup〉) showed a significant linear relationship with initial Olsen-P (〈em〉P〈/em〉 〈 0.01), with an increase of 4.2 mg kg〈sup〉−1〈/sup〉 desorbed P per 1 mg kg〈sup〉−1〈/sup〉 increase of initial Olsen-P. Ca〈sub〉2〈/sub〉-P exerted the conclusive effect on P desorption in the first four extractions, but Ca〈sub〉8〈/sub〉-P played a more important role in the 16 extractions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Ca〈sub〉8〈/sub〉-P was the greatest potential pool for P desorption after Ca〈sub〉2〈/sub〉-P was depleted. P desorption capacity was significantly linearly related to initial Olsen-P (〈em〉P〈/em〉 〈 0.01). Different fertilizer use strategies were developed based on P desorption capacity for soils with different initial Olsen-P levels. The present study provided basic data on how to reduce effectively the application amount of chemical P fertilizer.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Canal dredging and shaping produce considerable amounts of sediments whose reuse on- and off-site depends on their pollution level. This study explores the potential of a calcium chloride washing to remove potentially toxic elements (PTEs) from a freshly dredged calcareous sediment and to affect the aggregate stability of the washed sediment.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The ability of 0.5-M CaCl〈sub〉2〈/sub〉 washing to restore the sediment samples polluted with Cu and Zn dredged from a freshwater canal was assessed. The distribution of the two metals among the sediment geochemical phases, the potential availability to plants (DTPA), and the water aggregate stability of particles were evaluated on the washed samples and compared to control.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉In the most polluted sample (~200 and 500 mg kg〈sup〉−1〈/sup〉 of Cu and Zn, respectively), the washing decreased the amount of Cu by 26%, mainly in the sulfide/organic fraction, and of Zn by 10%, mainly in carbonates. A decrease in the dispersivity of clay fraction was observed due to the well-known effect of Ca〈sup〉2+〈/sup〉 ions on flocculation of colloidal clay particles. At large scale, the aggregates formed by the interaction between large particles and flocculated clay showed lower water stability with respect to the control, thus suggesting the need to improve the physical properties of the treated material. Noteworthy, after 1 year of dry storage from washing, the average percentage of potentially bioavailable (DTPA) Cu and Zn (23 and 13% of pseudo-total amount, respectively) dropped with respect to the control (40 and 19%) and a concomitant carbonate increase (+33%) was observed.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The CaCl〈sub〉2〈/sub〉 washing is a promising method to reduce Cu and, to a minor extent, Zn in wet calcareous sediments dredged from freshwater canals. However, there is still room for improvement. The PTE fractions remaining in carbonates and organic component of washed sediment clearly indicate the potential of combining mild acidic pH values with calcium chloride in the washing to enhance the PTE removal.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Loess landslides induced by irrigation are common geological disasters in the Loess Plateau, China. Long-term watering decreases the matric suction and soil strength of loess, thus causing the frequent occurrence of landslides. Therefore, studying the strength characteristics of unsaturated loess is of great significance for knowing how such landslides occur and, a step further, preventing them.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Undisturbed loess samples in Heifangtai Platform were collected to measure their soil water characteristic curves (SWCC) and a series of direct shear tests and triaxial shear tests were carried out with unsaturated loess. Moreover, the strength characteristics of the loess were discussed.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that in the direct shear test, the cohesion (〈em〉c〈/em〉) increased linearly with increasing matric suction whereas the suction internal friction angle (〈em〉φ〈/em〉〈sup〉〈em〉b〈/em〉〈/sup〉) was approximately constant. In the triaxial shear test, 〈em〉c〈/em〉 increased nonlinearly with increasing matric suction. The value of 〈em〉φ〈/em〉〈sup〉〈em〉b〈/em〉〈/sup〉 was a constant when matric suction was 0–100 kPa, but decreased as matric suction increased within the range of 100–200 kPa. The effective stress parameter (〈em〉χ〈/em〉) lay in the range from 0.5 to 0.8. When the matric suction was small, the shear strength calculated by Lu’s suction theory was almost the same as that obtained by Fredlund’s theory. With the increase of matric suction, the shear strength calculated by Fredlund’s theory gradually outperformed that of Lu’s suction theory. The shear strength calculated by the curve of moisture desorption was slightly larger than that of moisture absorption.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The variation trends of strength parameters with matric suction under the two tests were similar. The effective internal friction angles obtained by the triaxial shear test are slightly larger than those by the direct shear test. The suction internal friction angle (〈em〉φ〈/em〉〈sup〉〈em〉b〈/em〉〈/sup〉) was approximately a constant and smaller than 〈em〉φ〈/em〉´. The 〈em〉φ〈/em〉〈sup〉〈em〉b〈/em〉〈/sup〉 obtained by the direct shear test was slightly larger than that obtained by the triaxial test. Lu’s theory can be used to evaluate the stability of unsaturated soils on some loess slopes with high soil moisture content.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Chelate-assisted phytoremediation with biodegradable chelates has been considered to be a promising technique to enhance phytoremediation efficiency, while little information is available on phytostabilization. This study aims to assess NTA-assisted phytostabilization of Pb-contaminated soils by 〈em〉Athyrium wardii〈/em〉 (Hook.).〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A pot experiment was carried out to investigate the effects of different application days (1, 3, 5, 7, 10, 14, 21) of nitrilotriacetic acid (NTA) on plant growth, Pb accumulation, and Pb availability in rhizosphere soils of 〈em〉A. wardii〈/em〉 grown in soils contaminated with low (200 mg kg〈sup〉−1〈/sup〉) and high (800 mg kg〈sup〉−1〈/sup〉) concentrations of Pb.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉With the application of NTA, better growth for 〈em〉A. wardii〈/em〉 was observed when treated with NTA for 5–14 days for both low and high Pb soils, suggesting potential harvest time. Pb concentrations and Pb accumulation in underground parts of 〈em〉A. wardii〈/em〉 grown in low and high Pb soils increased with increasing application time of NTA generally. Similar changes were also found for bioaccumulation coefficients (BCFs) of 〈em〉A. wardii〈/em〉. The greatest remediation factors (RFs) for underground parts and whole plant of 〈em〉A. wardii〈/em〉 were observed for NTA application time of 7 and 5 days for low and high Pb soils, suggesting the greatest remediation efficiency. Furthermore, plant growth, BCF, and RF of 〈em〉A. wardii〈/em〉 grown in low Pb-contaminated soils were greater than those grown in high Pb-contaminated soils. Pb availability in rhizosphere soils of 〈em〉A. wardii〈/em〉 grown in low Pb soils was lower than those in high Pb-contaminated soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉It seems to be the optimum for 〈em〉A. wardii〈/em〉 to phytostabilize slightly Pb-contaminated soils with the application of NTA for 7 days as taking plant growth, Pb remediation efficiency, and environmental risk into consideration.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The objective of this study was to investigate the effects of amendment of different biochars on the physical and hydraulic properties of desert soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Biochars were produced with woodchip, rice straw, and dairy manure at temperatures of 300 and 700 °C, respectively. Each biochar at 5% (〈em〉w〈/em〉/〈em〉w〈/em〉) was mixed with desert soil, and the mixtures were incubated for 120 days.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The different biochar treatments greatly reduced soil bulk density and saturated hydraulic conductivity. Especially the rice straw biochar addition resulted in the lowest saturated hydraulic conductivities among the treatments. Biochar addition significantly increased water retention of desert soil at any suction. At the same suction and experimental time, the treatment with the rice straw biochar produced at the lower temperature resulted in higher water content than the other treatments. The biochar additions slightly enhanced formation of soil macro-aggregates in the early experimental time. However, the aggregate contents gradually decreased with time due to the lack of effective binding agents (e.g., soil organic matter and clay minerals).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The changes of hydraulic properties of desert soil were attributable to the biochar properties. The higher fine particle content, porosity, and surface hydrophilicity of rice straw biochars were the most beneficial properties to increase soil water retention and to reduce water flow in the desert soil. The improvement of hydraulic properties by biochar addition may provide a potential solution to combat desertification.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of this study was to determine the impacts of reduced aboveground and belowground C inputs on the community composition of soil microbes and enzyme activities in a seasonal context.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Litterfall removal, root exclusion, and stem girdling treatments under a subtropical conifer plantation growing on a coarse texture of sandy soil in southeast China were employed. One year after the initiation of the treatments, we measured the soil microbial biomass, community composition, and enzyme activities, including hydrolytic and oxidative extracellular enzymes on a seasonal basis. Soil inorganic N, dissolved organic C and N, and available P were also determined.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Seasonal variations of soil microbial composition and enzyme activities were attributed to soil temperature and moisture and soil nutrient availability. Girdling treatments significantly increased the abundances of gram-negative bacteria and actinomycetes in winter when soil temperature, moisture, and available nutrients were at the lowest level among the four seasons. Girdling alone and girdling combined with litter removal and root trenching significantly decreased the cellobiohydrolase, β-glucosidase, β-1,4-N-acetylglucosaminidase, and acid phosphatase activities in autumn. These hydrolytic enzyme activities were significantly correlated with soil moisture, NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉, DOC, and available P. We also found a significant relationship between hydrolytic enzyme activities and the ratio of gram-positive to gram-negative bacteria.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Plant belowground C allocation, soil temperature, and moisture drove the seasonal patterns of soil microbial composition and enzyme activities. Labile C input by root exudates is a key determinant of ecosystem functions mediated by soil microbes such as microbial decomposition processes.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉In this study, the pot experiments were performed to investigate that Pb and fluoranthene toxicity can be reduced and soil biological properties in co-contaminated soil can be improved by 〈em〉Oudemansiella radicata〈/em〉 (〈em〉O. radicata〈/em〉) combining with 〈em〉Serratia marcescens〈/em〉 (〈em〉S. marcescens〈/em〉).〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The soil used in this study was air-dried in 25 °C and sieved through a 2-mm mesh sieve, then was artificially contaminated with the different concentrations Pb. The microbial counts, the ligninolytic enzymes (Laccase and MnP), and soil enzymes (dehydrogenase and acid phosphatase) were analyzed by different methods. The Pb accumulation in mushroom and soils samples were analyzed by using the flame atomic absorption spectrometry (FAAS, SpectrAA-220Fs, United States Varian, Inc.). Fluoranthene content was analyzed using gas chromatograph-mass spectroscopy (GC–MS, Agilent 6890, USA).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Results showed that Pb and fluoranthene had a negative effect on soil biological properties and mushroom. 〈em〉S. marcescens〈/em〉 inoculation and 〈em〉O. radicata〈/em〉 cultivation mitigated the adverse impact and improved the soil biological characteristics. 〈em〉S〈/em〉. 〈em〉marcescens〈/em〉 inoculation could significantly increase the percentage of HOAc-extractable Pb and Pb concentration in 〈em〉O. radicata〈/em〉. Meanwhile, 〈em〉O. radicata〈/em〉 and 〈em〉S. marcescens〈/em〉 inoculation in soil could accelerate the removal of fluoranthene, and removal rate of fluoranthene was 86.39–91.95% in inoculated groups compared to 71.46–81.76% of non-inoculated groups (〈em〉P〈/em〉 〈 0.05). This study demonstrated that the interaction of 〈em〉O. radicata〈/em〉 and 〈em〉S. marcescens〈/em〉 was effective in promoting the bioremediation of co-contaminated soil with Pb and fluoranthene, and thus making it easier for us to detoxify the pollutants.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study investigated that potential of 〈em〉O. radicata〈/em〉 and 〈em〉S. marcescen〈/em〉 on the bioremediation of Pb-fluoranthene co-contaminated soil. The combined effect of 〈em〉O. radicata〈/em〉 and 〈em〉S. marcescen〈/em〉 could significantly promote the bioremediation of Pb-fluoranthene co-contaminated soil, especially for the twice inoculation of 〈em〉S. marcescen〈/em〉 groups. These results demonstrated that the presence of 〈em〉O. radicata〈/em〉 and 〈em〉S. marcescen〈/em〉 could significantly promote the bioremediation of Pb-fluoranthene co-contaminated soil, especially for the twice inoculation of 〈em〉S. marcescen〈/em〉 groups.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉How the stability of soil organic carbon (SOC) is affected by soil erosion is still not clear. The main purpose of this study was to characterize how SOC stability is affected by erosion and assess the effects of different soil properties on SOC stability.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soils from eroding and depositional sites in a typical small watershed in subtropical China were collected, and soil samples from four different depths (0–5, 5–10, 20–30, and 120–150 cm) were selected to represent the profile. Soil physicochemical properties as well as soil organic matter (SOM) chemical structure were measured. Thermal analysis and mineralization incubation experiments were performed to study the SOM stability. The effects of the soil properties on the SOM stability were evaluated via redundancy analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed that the eroding and depositional sites had different SOC contents but had similar organic functional groups. Furthermore, the OC in the eroded soils was more stable than that in the deposited soils, but this difference was only observed in the surface layers (0–5 and 5–10 cm). The selected variables (including soil texture, bulk density, pH, SOC, dissolved organic carbon (DOC), iron, soil aggregates, depth, erosion, and deposition) significantly explained the variations in SOC stability. A total of 91.4% of the variation in the thermogravimetry (TG)-T〈sub〉50〈/sub〉 (the temperature resulting in 50% of SOM loss) and 98.9% of the variation in the CO〈sub〉2〈/sub〉 emissions were explained by these variables. SOC alone contributed to 68% of the variation in the TG-T〈sub〉50〈/sub〉, whereas DOC individually contributed 93.9% of the variation in the CO〈sub〉2〈/sub〉 emissions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉SOC and DOC contents are the most important soil properties influencing SOC stability, and SOC stability affected by soil erosion is mainly by displacing SOM.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Soil organic carbon (SOC) in alpine regions is characterized by a strong local heterogeneity, which may contribute to relatively large uncertainties in regional SOC stock estimation. However, the patterns, stock, and environmental controls of SOC in semiarid alpine regions are still less understood. Therefore, the purpose of this study is to comprehensively quantify the stock and controls of SOC in semiarid alpine regions.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Soils from 138 study sites across a typical semiarid alpine basin (1755–5051 m, ~1 × 10〈sup〉4〈/sup〉 km〈sup〉2〈/sup〉) are sampled at 0–10, 10–20, 20–40, and 40–60 cm. SOC content, bulk density, soil texture, and soil pH are determined. Both a classical statistical model (i.e., a multiple linear regression, MLR) and a machine learning technique (i.e., a random forest, RF) are applied to estimate the SOC stock at a basin scale. The study further quantifies the environmental controls of SOC based on a general linear model (GLM) coupled with the structural equation modeling (SEM).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉SOC density varies significantly with topographic factors, with the highest values occurring at an elevation zone of ~3400 m. The results show that the SOC is more accurately estimated by the RF compared to the MLR model, with a total stock of 219.33 Tg C and an average density of 21.25 kg C m〈sup〉−2〈/sup〉 at 0–60 cm across the study basin. The GLM approach reveals that the topography is seen to explain about 58.11% of the total variation in SOC density at 0–10 cm, of which the largest two proportions are attributable to the elevation (44.32%) and the aspect factor (11.25%). The SEM approach further indicates that, of the climatic, vegetative, and edaphic factors examined, the mean annual temperature, which is mainly shaped by topography, exerts the most significant control on SOC, mainly through its direct effect, and also, through indirect effect as delivered by vegetation type.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The results of this study highlight the presence of high stocks of organic carbon in soils of semiarid alpine regions, indicating a fundamental role played by topography in affecting the overall SOC, which is mainly attained through its effects on the mean annual temperature.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Remediation of contaminated soils is of high relevance considering losses of this limited resource in most countries through erosion or through destruction for societal purposes. Most physicochemical remediation techniques lead to soil destruction avoiding reuse of the sites and loss of soil functions including ecological services like water retention/filtration, plant needs, carbon sequestration, or atmosphere restoration. This study aims to find out efficient telluric PAH-degrading fungi to both remediate soils and preserve their functioning.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Fifty telluric saprotrophic fungi were thus isolated from different aged PAH-contaminated soils sampled from four brownfields in the North of France. Thirty of these isolates were screened in a mineral medium for their ability to degrade benzo[a]pyrene (BaP) used as a model of HMW PAH. After 9 days of incubation, the remaining BaP was quantified through HPLC analysis. Then, a set of microcosms was performed with an aged PAH-contaminated non-sterile soil encompassing different approaches with bioaugmentation using mycelia of three strains pre-established on expanded clay particles and, for one of these strains, biostimulation strategies including nitrogen or nitrogen/phosphorous supplementations or aeration by stirring. After an incubation time of 30 days, remaining PAH were quantified through GC-MS and evolution of fungal populations evaluated through qPCR.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Isolated 〈em〉Penicillium canescens〈/em〉, 〈em〉Cladosporium cladosporioides〈/em〉, 〈em〉Fusarium solani〈/em〉, and 〈em〉Talaromyces helicus〈/em〉 degraded more than 30% of the initial 500 μg of BaP after 9 days of incubation. The three latest strains were thus inoculated in aged PAH-contaminated soil microcosms. After 30 days, PAH quantitative analyses showed that the highest degradation was obtained by bioaugmentation with 〈em〉T. helicus〈/em〉 (26% of the initial total PAH content: 321.7 mg kg〈sup〉−1〈/sup〉), which seems high considering an aged industrial contamination. Biostimulation approaches coupled to the inoculation of this strain did not improve the degradation. DNA quantification of the inoculated species confirmed their enrichment in the soil revealing the interest of the used inoculation strategy. We discuss bioaugmentation and biostimulation approaches in the case of the considered pollutants and soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉A strain identified as 〈em〉T. helicus〈/em〉 appears interesting for its HMW PAH degradation capacities both in mineral medium with pure BaP and in industrial non-sterile soil microcosms contaminated with a hydrocarbon complex mixture. This study also confirms the efficiency of a well-studied BaP-degrading strain of 〈em〉F. solani〈/em〉. These results indicate the potentialities of the used bioaugmentation approach and underline the necessity of scale-up strategies to apply this kind of technique on site.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Spectrocolourimetric measurements provide a relatively inexpensive, quick and non-destructive alternative to the analysis of geochemical and organic matter properties. When used in the analysis of sediments and their potential sources, these colour parameters may provide important information on the dominant processes (i.e. erosion) occurring in the Critical Zone. Here, they are used to investigate whether eroded sediment is derived from forest (i.e. natural), cultivated (i.e. anthropogenic) or subsoil sources in order to assess their potential to monitor the effect of decontamination in regions impacted by fallout from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Fifteen spectrocolourimetric properties (L*, a*, b*, C*, h, x, y, z, L, a, b, u*, v*, u’, v’) were measured in potential source (〈em〉n〈/em〉 = 37) and sediment (〈em〉n〈/em〉 = 400) samples collected during 13 campaigns from 2011 to 2017 after major flood events in two catchments (total surface area of 450 km〈sup〉2〈/sup〉) draining the main FDNPP radioactive pollution plume. Potential sources included topsoil from forest and cultivated sources along with subsoil material originating from landslides, channel banks and the decontamination of cultivated areas. The optimum set of parameters used in the mixed linear model to calculate the sediment source contributions was obtained through the use of a range test, the Kruskal–Wallis 〈em〉H〈/em〉 test and a linear discriminant analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Nine selected colour parameters correctly classified 100% of the source samples (i.e. forest, subsoil and cultivated sources). The results illustrate that cultivated landscapes were the main source of sediment to these river systems (mean 56%, SD 34%) followed by subsoil (mean 26%, SD 16%) and forest sources (mean 21%, SD 24%). However, these contributions varied strongly over time, with a peak of subsoil contributions (mean 57%, SD 17%) in Fall 2015, coinciding with the occurrence of a typhoon after the remediation works. These results were consistent with monitoring studies conducted in the same area that showed the major impact of typhoon Etau in September 2015 on sediment and radiocaesium fluxes.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉These original results demonstrate that spectrocolourimetric measurements may contribute to the routine monitoring of the effectiveness of remediation works in this post-accidental context. Owing to the inexpensive, rapid and non-destructive analyses, spectrocolourimetric-based tracing methods have significant potential to provide information on the dominant erosion processes occurring in the Critical Zone.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉To determine whether supplemental selenium (Se) enhances the tolerance of 〈em〉Conyza canadensis〈/em〉 (〈em〉C. canadensis〈/em〉) to polycyclic aromatic hydrocarbons (PAHs) and thereby accelerates PAH dissipation in soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉We examined the dissipation of different concentrations of two PAHs, phenanthrene (PHE) and pyrene (PYR), from contaminated soils after 60 days of growth of 〈em〉C. canadensis〈/em〉 supplemented with or without a low level of Se (0.5 mg kg〈sup〉−1〈/sup〉) in a pot culture experiment. PAH concentrations were 0, 50, 200, and 800 mg kg〈sup〉−1〈/sup〉. Response variables included plant biomass, PAH accumulation in plants, soil microbial biomass carbon (MBC), root morphogenesis, antioxidant enzyme activity, and PHE/PYR dissipation.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Plant biomass and root morphogenesis decreased with increasing PAH concentration, whereas malondialdehyde concentration, an indicator of oxidative stress, increased. Catalase activity, total superoxide dismutase activity, MBC, and the PAH dissipation ratio all increased with increasing PAH concentration until 800 mg kg〈sup〉−1〈/sup〉. Se supplementation of soil increased the tolerance of 〈em〉C. canadensis〈/em〉 to PAHs and significantly increased PAH phytoremediation after 60 days of plant growth. The PHE dissipation ratios with and without Se supplementation were 57 ± 3% and 28 ± 8%, respectively, and PYR dissipation ratios were 30 ± 7% and 24 ± 8%. The increase in the PAH dissipation ratio with Se supplementation was largest in PHE-contaminated soils at 800 mg kg〈sup〉−1〈/sup〉.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉A low concentration of supplemental Se in soil enhances the dissipation of PHE and PYR by 〈em〉C. canadensis〈/em〉. This enhancement is due to an increased plant tolerance toward PAHs, which results in increased 〈em〉C. canadensis〈/em〉 biomass, soil MBC, and decreased plant uptake of PAHs. This study suggests that Se supplementation can contribute to ongoing efforts to develop effective phytoremediation systems for soils contaminated with PAHs.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉This study was conducted to evaluate the synergistic effects of organic amendments and soil water status on trace metal release from serpentine soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Two organic amendments, dendro-biochar (BC) and municipal solid waste compost (CM), were added to serpentine soil at four different ratios, specifically 2.5:0.0, 2.5:1.0, 2.5:2.5, and 2.5:5.0% (〈em〉w〈/em〉/〈em〉w〈/em〉). Along with the control (with no organic amendments), each soil treatment was incubated separately under saturated point (SP) and field capacity (FC) water content for 10 days. Subsamples were obtained from each treatment to analyze the bioavailable trace metal concentration and related edaphic parameters, namely total organic carbon (TOC), nitrate (NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉), phosphate (PO〈sub〉4〈/sub〉〈sup〉3−〈/sup〉), and cation exchange capacity (CEC). Then, the soil solution was eluded from each treatment and incubated for 10 days under permanent wilting point (PW). Furthermore, a seed germination test was performed under the different treatments.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Significant reductions (〈em〉p〈/em〉 〈 0.05) in bioavailable concentration of all four trace metals were observed in all the amendment ratios under all water status treatments (SP, FC, SP-PW, and FC-PW), compared with the control. Furthermore, FC-PW with the highest amendment ratio (2.5% BC:5.0% CM) reduced Ni by 67.6%; FC-PW with 2.5% BC + 2.5% CM immobilized Mn and Co by 92.1 and 96.9%, respectively, and SP water status with all four amendment ratios immobilized 100% of bioavailable Cr. Maximum amendment ratio under all four water status enhanced %TOC and significantly increased PO〈sub〉4〈/sub〉〈sup〉3−〈/sup〉 concentration in SP-PW. However, FC showed comparatively high NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 concentration than other treatments. Germination index (GI) for mung beans and tomato did not show a significant difference in response to amendment ratios or soil water status; however, SP treatment expressed significantly high seedling vigor (SVI) for mung beans.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Treatments of BC and CM effectively immobilize the bioavailable fraction of trace metals in serpentine soils. Increasing amendment ratio increases the %TOC regardless of the soil water status, whereas SP-PW is favorable for the availability of PO〈sub〉4〈/sub〉〈sup〉3−〈/sup〉, and FC is favorable for availability of NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉. The GI for mung beans and tomato seed was not influenced by the soil water status nor by the amendment ratios. However, the SVI of mung bean seedlings was controlled by the soil water status.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The farming practices of ridge-furrow with film mulching (RFFM) have been extensively reported as a valuable technique for improving crop productivity and enhancing water-use efficiency. However, research on the high-yield mechanism of RFFM measures under drought stress from the perspective of microbial diversity has been scared.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Field experiments were conducted to analyze the effects of conventional flat planting (FP), no film mulching (NR), white polyethylene film mulching (WR), black polyethylene film mulching (BR), and biodegradable film mulching (BDR) with 40 and 80 cm furrow width levels on soil temperature, soil water storage (SWS), microbial carbon utilization, and yield of winter oilseed rape.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The RFFM significantly increased the SWS as well as rapeseed yield and yield components. However, these treatments did not cause obvious differences in soil temperature. A relative high value of average color change rate (AWCD) was observed during the incubation time of 24–216 h, and it reached the peak value at 240 h. The AWCD in the furrow with 80 cm width was greater than that of 40 cm. The RFFM also could improve the utilization intensities of soil microorganism on the carbon sources of carbohydrates, amino acids, and miscellaneous in rapeseed rhizosphere. This result was consistent with that of the principal component analysis. The Shannon–Wiener diversity index, Simpson’s diversity index, and Shannon–Wiener evenness in BDR〈sub〉40〈/sub〉, BR〈sub〉40〈/sub〉, and BR〈sub〉80〈/sub〉 were significantly higher than other treatments, respectively. In addition, correlation analysis results suggested that the indicator of affecting the diversity of carbon source was mainly due to the water storage capacity.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The methods of film mulching have a remarkable effect on microbial diversity. The yield of BR and BDR were significantly higher than other treatments. Compared with FP, RFFM increased rapeseed yield by 9.61–86.10%. In the year of less rainfall, production has decreased in comparison with the first season, while BDR〈sub〉80〈/sub〉 guarantees continuous high yield and substantially promoted carbon utilization and soil microbial diversity. Soil microbial diversity is positively correlated with soil water content, which is beneficial to increase production. Wider furrow (80 cm) is recommended a sustainable high-yield method due to convenient labor in the region in Southwest China.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of this study was to investigate biodegradation of γ-hexabromocyclododecane (γ-HBCDD) under conditions mimicking three bioremediation strategies: (i) biostimulation: addition of sodium formate and ethanol to stimulate biodegradation as the carbon source and electron donor, respectively; (ii) bioaugmentation: addition of an enrichment culture of 〈em〉Dehalobium chlorocoercia〈/em〉 strain DF-1; and (iii) natural attenuation: no amendments. To differentiate between biotic and abiotic mechanisms affecting γ-HBCDD degradation, four control microcosms were set up as sterile, negative, abiotic, and contaminant control.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Sediment microcosms were prepared in 20-mL bottles and operated as duplicate sacrificial reactors with a sediment-to-liquid ratio of 3 g wet solid:3.5 mL liquid. Total incubation time was 36 days with sampling every 4 days, except the last day. γ-HBCDD contents of sediments were extracted using ultrasonication and analyzed using GC-MS. Four control microcosms were used to observe the effect of (i) microbial activity (sterilization with mercuric chloride and autoclaving), i.e., sterile; (ii) microbial culture without DF-1 cells, i.e., negative control; (iii) sediments, where kaolinite is used instead of sediments, i.e., abiotic control; and (iv) γ-HBCDD, where no analyte is added, i.e., contaminant control.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Biostimulation showed the highest γ-HBCDD biodegradation rate (〈em〉k〈/em〉 = 0.0542 day〈sup〉−1〈/sup〉) and enhanced biodegradation compared to natural attenuation (〈em〉k〈/em〉 = 0.0155 day〈sup〉−1〈/sup〉). Bioaugmentation (〈em〉k〈/em〉 = 0.0123 day〈sup〉−1〈/sup〉) with DF-1 strain showed a sharp decrease at the beginning, but could not maintain this trend afterwards. Paired comparison of microcosms yielded no statistically significant difference between bioaugmentation and natural attenuation; hence, DF-1 strain did not improve degradation when compared to natural attenuation. This was also substantiated by observations from the negative control set. Sterile and abiotic control sets showed no significant concentration change in time. Consequently, adsorption was not considered as a significant mechanism acting on γ-HBCDD concentration change in our sediment microcosms. Thus, γ-HBCDD decrease observed in bioremediation microcosms was attributed to microbial activity.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We reported effective analyte degradation with biostimulation. This was the first study to test bioaugmentation for HBCDD degradation, but we observed no enhancement of degradation with the DF-1 strain tested. Previous studies observed HBCDD reduction in their sterilized controls, hence reported total biotic and abiotic degradation rate. In this study, comparative evaluation of three test and four control microcosms enabled identification of only anaerobic biodegradation rates for γ-HBCDD, providing useful information for bioremediation of contaminated sites.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The use of humic substances is under thorough discussion of state-of-the-art agricultural science. They are marketed mostly as concentrated aqueous solutions of potassium or sodium humates, which are produced by alkali extraction of raw organic matter such as lignite, leonardite, or peat. Due to the presence of clay minerals in the raw materials, humate solutions are characterized with a substantial content of silicates. At the same time, rapid quantification techniques for selective determination of humic components and silicates in humate solutions are missing. The aim of this work was to develop an IR spectroscopic technique for rapid quantification of humic substances (HSs) and silicates in concentrated humate solutions with the minimum sample preparation, which could be used for quality control of humic fertilizers.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Sodium humate from Sigma-Aldrich and two potassium humate fertilizers available on the market were used for the experiments. For FTIR measurements, thin-layer open-cell (DialPath) transmission and attenuated total reflectance (ATR) accessories were used. The secondary focus of this work was the use of a compact portable IR spectrometer, which can be used in the field. Total carbon analyzer and ICP-AES for determination of silicon and aluminum contents were used.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉FTIR spectra were registered for both dry samples and aqueous solutions of the humates. The most intense bands in IR spectra of HS were characterized with linear concentration dependences in the range of concentrations of 2–200 g L〈sup〉−1〈/sup〉 of HS. The most sensitive band was shown to be 1560 cm〈sup〉−1〈/sup〉. It corresponded to carboxyl groups (COO〈sup〉−〈/sup〉) of humates (limits of detection [recalculated to carbon] for transmission and ATR modes are 3 and 1 g L〈sup〉−1〈/sup〉, respectively). The band at 1015 cm〈sup〉−1〈/sup〉 was attributed to silicate. It did not overlap with the bands of organic constituents and could be used for silicate quantification. The proposed technique can identify different trademarks of the fertilizers by the amount of both HS and silicate.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Rapid determination of humate and silicate components comprising three samples of humic fertilizers was proposed without isolation of the analytes from solution.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Accounting for ionic strength and ion association, the degree of calculated supersaturation with CaCO〈sub〉3〈/sub〉 of gleyic solonetz and molic solonetz soil solution is high. The purpose of the research was to reveal the effect of the water-dissolved organic matter (DOM) on the calcium carbonate equilibrium (CCE) in soil solution, to create a thermodynamic model of carbonate association and complexation with DOM and heavy metals (HMs), and to correct the principal of soil management.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Object of research—Kastanozem complex of the dry steppe, Rostov Oblast, Russia. The water extraction of soluble salts was made at the water-to soil-ratio 5:1 and analyzed using standard methods. DOM content was determined by Strosser (J Agrobiol 27:49–60, 〈span〉2010〈/span〉). The soil solution macro-ion equilibrium composition was calculated using ION-2 program (Endovitsky et al. 〈span〉2009〈/span〉). DOM role in soil solution supersaturation with СаСО〈sub〉3〈/sub〉 was assessed, comparing C content in real solution and in identical artificial solution prepared without organic matter. Taking into account the ion association, the molar fractions of free and bound HM ion were calculated using microelement association coefficient, 〈em〉k〈/em〉〈sub〉as(ME)〈/sub〉. The soil liquid-phase saturation with CaCO〈sub〉3〈/sub〉 was characterized by the ratio of the real solubility product (〈em〉S〈/em〉) to the thermodynamic solubility product (〈em〉S〈/em〉〈sup〉0〈/sup〉): 〈em〉К〈/em〉 = 〈em〉S〈/em〉/〈em〉S〈/em〉〈sup〉0〈/sup〉.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The soil solution supersaturation with CaCO〈sub〉3〈/sub〉 was characterized by the product of analytical concentrations (〈em〉S〈/em〉), equilibrium concentrations [accounting ion activity (〈em〉S〈/em〉〈sup〉I〈/sup〉), ion association (〈em〉S〈/em〉〈sup〉II〈/sup〉), ion association and complexation (〈em〉S〈/em〉〈sup〉III〈/sup〉)], and the thermodynamic solubility product (〈em〉S〈/em〉〈sup〉0〈/sup〉). To evaluate the role of DOM in soil solution supersaturation with CaCO〈sub〉3〈/sub〉, the initial pure Ca (HCO〈sub〉3〈/sub〉)〈sub〉2〈/sub〉 solution series was prepared. The humic and fulvic acids from the illuvial horizon of gleyic solonetz with concentrations of 20 mg C L〈sup〉−1〈/sup〉 and 120 mg C L〈sup〉−1〈/sup〉 decreased the CaCO〈sub〉3〈/sub〉 precipitation compared with initial soil solution. The release of CaCO〈sub〉3〈/sub〉 from soil water extracts containing water-soluble organic matter was 1.2–1.9 times less compared with identical artificial solution not containing organic matter. The HM binding by carbonates is proportional to the DOM content.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉In molic solonetz and gleyic solonetz, the neutralization of the soda should be assessed by the soil solution supersaturation with CaCO〈sub〉3〈/sub〉. To calculate the degree of HM passivation in soil solution containing DOM, the coefficient of soil solution oversaturation with CaCO〈sub〉3〈/sub〉 is proposed. For reducing soil organic matter and DOM mobility and loss from soil, as well as for Pb passivation, intra-soil mechanical processing, intra-soil waste management, and intra-soil watering are proposed.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The study of interactions between humic substances (HSs) and soil filamentous fungi is the key to understanding the sustainable soil functioning. The present work aims to examine the decomposition of HSs by filamentous dark-pigmented fungus 〈em〉Alternaria alternatа〈/em〉 under the laboratory conditions and to determine the effect of easily assimilable organic carbon on this process. Analyzing such polydisperse substances like HSs by a complex integrated methodology makes it possible to explore the data on their decomposition by microorganisms.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉To achieve the aforementioned goals, we used chromatographic and spectroscopic approaches: low-pressure size-exclusion and hydrophobic interaction chromatography accompanied by absorption and fluorescence spectroscopy. To determine the effect cometabolism conditions produced on HS decomposition, two types of carbon substrates were added to the nutrient media: easily assimilable organic carbon (standard 0.3% or reduced 0.03% sucrose content) and hardly assimilable organic carbon (HSs), as well as their combinations. Five HS samples of different organic matter origin have been inspected: potassium humates (HPs) and humic acids (HAs) from coal, peat, and lignosulfonate. Correlation matrix and principal component analysis (PCA) were calculated for comprehensive data analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Transformations of the investigated HSs under fungal cultivation lead to the increase in the low molecular weight fraction, rise of hydrophilic fraction, enlargement of absorbance ratio A〈sub〉250〈/sub〉/A〈sub〉365〈/sub〉, shortening of the emission wavelength of the humic-type fluorescence, and growth in the fluorescence quantum yield measured with excitation at 355 nm. A positive correlation was observed between the accumulation of fungal biomass and the degree of HS decomposition. PCA analysis confirms that the difference in the results of HS decomposition largely depends on the sucrose content and the nature of HSs. We divided all the HS samples into four groups according to the degree of HS decomposition: original HS solutions, HPs altered using fungal cultivation at 0.03% sucrose, HAs after fungal cultivation at 0.03% sucrose, and finally, HSs (both HPs and HAs) after fungal cultivation at 0.3% sucrose.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉In the laboratory experiments, we showed that (1) the isolated HAs were more effectively degraded than the parent HPs, and this process was more pronounced at a reduced sucrose content, and (2) the decomposition of stable organic compounds (HSs) was activated by the easily assimilable carbon sources (especially 0.3% sucrose) being present. We assume that it is the easily assimilable organic carbon that most likely triggers the HS degradation working as the 〈em〉priming effect〈/em〉 in natural environments.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Adsorption onto mineral and bacterial surfaces can profoundly affect the mobility and fate of dissolved ions in soils; however, currently, there is a poor understanding of antimony (Sb) adsorption onto mixture of these two sorbents. This study aims at investigating the adsorption of Sb(III) to an antimony-tolerant soil bacterium 〈em〉Bacillus cereus〈/em〉 and cell-goethite binary composite under anaerobic condition.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Adsorption isotherms and adsorption edges (pH 3–10) were conducted to explore the adsorption capacity of Sb(III) to goethite, bacteria, and the cell-goethite composite. X-ray photoelectron spectroscopy (XPS) was applied to determine the surface functional groups that are responsible for Sb adsorption.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Scanning electron microscope shows that nano-particulate goethite is strongly adsorbed onto the cell surfaces to give a mineral film. The cell-goethite composite displays an additive Sb adsorption behavior, i.e., composite adsorptivity is the sum of the individual end-member metal adsorptivities (i.e., the additivity rule). Sb(III) adsorption to goethite, 〈em〉Bacillus cereus〈/em〉 cells, and the cell-goethite composite is independent of pH. Using high-resolution XPS spectra, we identify the ferric hydroxyl functional groups of goethite and the carboxyl and amino/amide groups of bacteria responsible for Sb binding to the binary solid products. Moreover, the molecular binding mechanisms are very similar between the composite and the isolated end-member bacteria and mineral phases.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Sb(III) adsorption to the bacteria-goethite conforms to a component-additive rule. Goethite component plays a more important role in Sb binding to the bacteria-mineral composite. New findings of this research suggest that it should be careful to use the universal adsorption rule for cations as previously suggested, to simulate anion adsorption to organo-iron oxide composite.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Sustainable land management is considered an effective measure to ensure national food security by matching improved soil quality with enhanced crop productivity. The objectives of the present study were to evaluate soil quality status among paddy fields, vegetable fields, and pomelo orchards managed by continuous cropping systems, to establish a minimum data set (MDS) and recommend fertilization strategies to enhance productivity in acidic red soil hilly regions.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The soil quality index (SQI) was calculated using the total data set (TDS) and MDS as indicator selection methods. A total of 51, 32, 44 soil samples (0–20 cm) were collected from different cropping systems in paddy fields, vegetable fields, and pomelo orchards, respectively. Eleven soil properties (geographical indicator (altitude) and 10 chemical parameters) were measured to evaluate soil quality of acidic red soil hilly regions in Pinghe County, Fujian province, southern China.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results showed significant differences in soil quality indicators between paddy fields, vegetable fields, and pomelo orchards, and altitude, total N, hydrolysable nitrogen (Avail-N), exchangeable calcium (Avail-Ca), and available zinc (Avail-Zn) were adopted as indicators in the MDS using principal component analysis (PCA). After scoring and weighting the selected indicators, the mean SQI scores of paddy field, vegetable field, and pomelo orchard soils were 0.267, 0.282, and 0.236 for TDS, respectively, and the SQI scores were 0.233, 0.256, and 0.166 for MDS. A significant positive correlation was observed between SQI and crop yield using both the TDS and MDS methods, indicating that the MDS method adequately represents the TDS method (〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.6839) for evaluation of the effects of farming production practices on soil quality. Overall, the unbalanced soil quality indicators, including rich in total N, organic matter and Avail-P, and deficient in Avail-N, Avail-K, Avail-Ca, Avail-Mg, Avail-Zn, and Avail-B, were implicated as the main limiting factors for crop production in the studied regions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Compared with paddy and vegetable fields, the lower total N and Avail-N status at higher altitudes were considered as the major factors limiting pomelo productivity. Therefore, there is a great potential for increasing pomelo productivity by improving soil quality with integrated nutrient management in acidic red soil hilly regions.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Antimony (Sb) is a highly toxic heavy metal, and its amount in soil is increasing due to anthropogenic activities. Excessive Sb intake could ultimately threat human health. Recently, biochar (BC) has been accepted for remediation of Sb-contaminated soil. Understanding the interaction between BC and Sb and the effect of BC-induced changes in soil properties on immobilization/mobilization of Sb will help, therefore, to elucidate the mechanism of BC in immobilization/mobilization of Sb in contaminated soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Wheat straw-derived BC (SBC) and fruit (apple) tree-derived BC (FBC) were obtained at the pyrolysis temperatures of 500 °C. Sb-contaminated soil was incubated with/without 0.5, 5, or 10 wt% of SBC and FBC for 130 days. Change of soil properties induced by BC was explored during the incubation. Dynamic change of Sb fraction and speciation were assessed by the sequential chemical extraction and citric acid extraction, respectively. The X-ray photoelectron spectroscopy (XPS) was employed to check elemental change of soil with 10% SBC at different incubation times. The correlation analysis and principal component analysis (PCA) were used to analyze relationship between Sb immobilization/mobilization and change of soil properties induced by BC.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The obvious change of soil properties can be observed when the soil was treated with 10% BC instead of 5 and 0.5% BC. During the first 20 days with SBC incubation and 50 days with FBC incubation, Sb mobilization increased may be because of the electrostatic repulsion of functional groups in BC; OM and functional group of BC govern the reduction reactions, anionic competition, electrostatic repulsion, and biological reduction in soil induced by BC. By contrast, after 20 days with SBC incubation and 50 days with FBC incubation, the mobilization of Sb decreased, which may be attributed to the formation of complexes between Sb and OM of BC, secondary mineral precipitation, and organic complex between Sb and humus acid in soil induced by BC.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉It is noteworthy that the application of BC has a potential mobilizing risk for Sb and the final effect depends on BC characteristic and the change of soil properties induced by BC. The possible risks induced by BC should be considered before applying the BC to Sb-contaminated soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of the work is to compare the biological activity of carbonic nano-structures of natural and artificial origination, namely, humic substances (HS) and fullerenols.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The representative of the fullerenol group, С〈sub〉60〈/sub〉О〈sub〉〈em〉y〈/em〉〈/sub〉(OH)〈sub〉〈em〉x〈/em〉〈/sub〉 where 〈em〉у〈/em〉 + 〈em〉x〈/em〉 = 20–22, was chosen. Enzyme-based luminescent bioassay was applied to evaluate toxicity and antioxidant properties of HS and fullerenol (F); chemiluminescent luminol method was used to study a content of reactive oxygen species (ROS) in the solutions. Toxicity of the bioactive compounds was evaluated using effective concentrations 〈em〉ЕС〈/em〉〈sub〉〈em〉50〈/em〉〈/sub〉; detoxification coefficients 〈em〉D〈/em〉〈sub〉OxT〈/sub〉 were applied to study and compare antioxidant activity of the compounds. Antioxidant activity and ranges of active concentrations of the bioactive compounds were determined in model solutions of organic and inorganic oxidizers—1,4-benzoquinone and potassium ferricianide.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉Values of 〈em〉ЕС〈/em〉〈sub〉〈em〉50〈/em〉〈/sub〉 revealed higher toxicity of HS than F (0.005 and 0.108 g L〈sup〉−1〈/sup〉, respectively); detoxifying concentrations of F were found to be lower. Antioxidant ability of HS was demonstrated to be time-dependent; the 50-min preliminary incubation in oxidizer solutions was suggested as optimal for the detoxification procedure. On the contrary, F’ antioxidant effect demonstrated independency on time. Antioxidant effect of HS did not depend on amphiphilic characteristics of the media (values of 〈em〉D〈/em〉〈sub〉OxT〈/sub〉 were 1.3 in the solutions of organic and inorganic oxidizers), while this of F was found to depend: it was maximal (〈em〉D〈/em〉〈sub〉OxT〈/sub〉 = 2.0) in solutions of organic oxidizer, 1,4-benzoquinone.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Both HS and F demonstrated toxicity and low-concentration antioxidant ability; however, quantitative characteristics of their effects were different. The differences were explained with HS polyfunctionality, higher ability to decrease ROS content, non-rigidity, and diffusion restrictions in their solutions. Antioxidant effect of the bioactive compounds was presumably attributed to catalytic redox activity of their 〈em〉π〈/em〉-fragments. The paper demonstrates a high potential of luminescent enzymatic bioassay to study biological activity of nano-structures of natural and artificial origination.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉This study aims to investigate the presence of aggregate hierarchy during the decomposition of rice straw in a subtropical soil (Ultisol) with large quantities of Fe and Al oxides and in two temperate soils with a large amount of montmorillonite (Vertisol) or with less organic matter but a large content of CaCO〈sub〉3〈/sub〉 (Inceptisol) and to explore the relationship between relative contributions of biotic and abiotic processes in soil aggregation and the presence of aggregate hierarchy.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉A 120-day incubation experiment with or without 〈sup〉13〈/sup〉C-labeled straw was conducted in the above-mentioned three soils previously sieved at 〈 0.25 mm (i.e., without macroaggregates). During incubation, the aggregate size distribution, aggregate associated organic C (OC), straw-derived 〈sup〉13〈/sup〉C, soil respiration, soil microbial biomass C and N, and phospholipid fatty acids were measured several times.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉At the end of each experiment, both macro- and microaggregates were present. Higher OC and 〈sup〉13〈/sup〉C concentrations in macroaggregates than in the fractions 〈 0.25 mm were observed within the first 15 days in all three soils. However, after 60 days, only the Vertisol could still show a slightly higher OC concentration in the macroaggregates. Same as the temperate Vertisol and Inceptisol, more macroaggregates could form by organic binding agents than by inorganic binding agents in the Ultisol at the early incubation stage. While similar to the subtropical Ultisol, macroaggregates could also mainly form by inorganic binding agents than by organic binging agents in the Vertisol and Inceptisol at the later stage. Despite the microbial community structure being different from each other, the macroaggregation was significantly related to the microbial biomass and activity in all three soils at the early incubation stage.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉A high degree of aggregate hierarchy can present in all three soils at the early decomposition stage of rice straw, while at the later stage, no aggregate hierarchy or only a small degree of aggregate hierarchy can present in the Ultisol and Inceptisol or in the Vertisol. Consequently, instead of soil type, the expression of aggregate hierarchy is essentially determined by the relative contributions of biotic and abiotic processes or of organic and inorganic binding agents in soil aggregation.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉Are rare earth element (REE) patterns employable as tracers in human interventions of bulk soil disturbances, when high concentrations of metals are involved in the in situ soil disturbance? In terms of bulk soil disturbance, it is difficult to distinguish between bulk soil disturbances and emplacement of new earthen material. Chemical fingerprinting, in particular REE plus yttrium, is applied across many fields, but predominantlyin tracking the sources of potential environmental contaminants.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The REE normalised patterns (HNO〈sub〉3〈/sub〉:HF:HCl 3:1:1 digestion, ICP-MS) of two Calcaric Cambisols were compared with those of a Geric Ferralsol (Novic, Technic) originated from selective overburden of nickel mining (20°40′ N, 75°35′ W).〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The sum of REE, including Y and Sc, ranged between 48 and 101 mg kg〈sup〉−1〈/sup〉. Principal component analysis (PCA) shows a discriminant role of REE. REE signature normalised to the upper continental crust shows slight positive Eu and negative Ce anomalies in the case of both Calcaric Cambisols, while the Geric Ferralsol shows anomalous patterns with the same anomalies plus a slight positive anomaly of Y, as a consequence of the addition of mining by-products.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Here, we show that REE patterns of the individual horizons of a soil have characteristics that allow us to distinguish undisturbed from soils mixed with other soil materials, including those with different pH values and high metal contents (e.g. Cr, Mn, and Ni ≥ 0.5%, Fe ≫ 5 wt%). Our results demonstrate, by using soils with contrasting characteristics, that their origins can be traced via the patterns of their REEs, even in the presence of high concentrations of other metals. In perspective, when background maps of all REE elements in soils are available worldwide on an appropriate scale, this enables us to obtain a level of discriminatory detail on a local scale.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The aim of the present work was to study the effect of humic preparation on the yielding capacity of winter wheat, the dynamics of mineral nutrients in the rhizosphere, and the activity of rhizosphere microbial community, as well as the protective properties of humate treatment under the stress caused by the application of a sulfonylurea herbicide.〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉The humic preparation BIO-Don is prepared from vermicompost by alkaline extraction. The effect of humic preparation was estimated in a field experiment. The contents of the mobile ammonium and nitrate, exchangeable potassium, phosphorus, and humus were determined. Sampling and nutrient determination were performed in the tillering, booting, and grain maturing stages. Production experiments on the study of the combined effect of the humic preparation and the sunfonylurea pesticide Granstar Pro were performed in 2015 and 2017. The dynamics of mobile phosphorus in soil was studied. The abundance of culturable bacteria in the rhizosphere and bacterial species with different ecological strategies was determined. The dominant bacterial species were identified by MALDI-TOF mass spectrometry.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The results of a small-plot experiment showed that at the tillering stage, the use of humic preparation has led to significantly higher supply of soil with mobile phosphorus. The winter wheat yield was 32.0 dt/ha in the control and 39.2 dt/ha with humic preparation or 22.5% gain in yield. The results of production experiment show that the application of sulfonylurea herbicide induced a chemical stress on winter wheat plants, but the use of humic preparation reduced this effect and increased the availability of phosphorus compounds. The treatment of plants with pesticides caused the general decrease in abundance of bacteria in the rhizosphere. The effect on quickly growing bacteria is more pronounced, while slowly growing bacteria and fungi are more resistant to this impact.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The application of humic preparation to winter wheat plantations allows to decrease the toxic effect of sulfonylurea herbicide, improve the supply of soil with mineral nutrients, and increase the crop yield. The favorable effects of humic preparation can be related to the active regulation of phosphorus mobilization by plants through the mechanism of root exudates due to the activation of root microbiota.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Purpose〈/h3〉 〈p〉The purpose of this work is to identify the most probable structural fragments of the tundra and the taiga soil humic acids on the basis of computer analysis of their IR spectra〈strong〉.〈/strong〉〈/p〉 〈/span〉 〈span〉 〈h3〉Materials and methods〈/h3〉 〈p〉Humic acid (HA) samples were isolated from 11 northern soils of the Komi Republic, Russia. IR spectra were registered in KBr by Bruker FTIR spectrometer Vector-22. IR EXPERT information-analytical system was used for analysis of these spectra. This system is a combination of an extensive database (more than 50,000 correlation records of “IR spectrum–structure–structural fragments–accompanying information”) and software modules that allow solving various spectral-structural tasks.〈/p〉 〈/span〉 〈span〉 〈h3〉Results and discussion〈/h3〉 〈p〉The procedure of working with new IR spectra of humic acid involved two stages. Comparison of the sample IR spectrum with all spectra in IR-EXPERT databases was followed by decomposition of the closest spectral analogs into the set of fragments which is individual for each HA. This unique representation makes it possible to associate a spectrum with a combination of structural fragments rather than with the exact structure. That is what we need for HA. The analysis of the obtained ten-vertex fragments shows that all HA samples contain linear, slightly branched, conjugated chains of double C–C bonds, as well as the fragments of aromatic amines and amides.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Using only IR spectroscopy data and the IR EXPERT system, we were able to show that humic acids of these northern soils are predominantly aliphatic and contain a large number of oxygen-containing groups, which allows one to predict their high reactivity when interacting with ecotoxicants.〈/p〉 〈/span〉

Description: 〈p〉Incorrect and incomplete wording: Funding information. The study was funded by the RFBR research project no. 18–016-00078. Correct and complete wording: Funding information. The study was funded by the RFBR research projects no. 18–016-00078, 18–04-01218.〈/p〉