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  • Articles  (314)
  • nitrogen  (157)
  • geostatistics  (120)
  • kinetics
  • Springer  (314)
  • Periodicals Archive Online (PAO)
  • Geosciences  (207)
  • Energy, Environment Protection, Nuclear Power Engineering  (109)
  • 1
    Electronic Resource
    Electronic Resource
    Integrated Interpolation Methods for Geophysical Data: Applications to Mineral Exploration (2000)
    Springer
    Natural resources research 9 (2000), S. 53-64 
    Details
    ISSN: 1573-8981
    Keywords: Geophysical data integration ; geostatistics ; mineral exploration ; interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Geophysical data are used routinely in mineral exploration to delineate the geology of an area.Because geophysical attributes are sparsely sampled, interpolation methods are used to gridthe individual sets of data. Whereas traditional techniques interpolate constituent attributes ofinterest independently, frequently resulting in simplistic geological models, alternativetechniques interpolate by integrating secondary data sets collected in the explored area. Traditionaltechniques include minimum curvature and ordinary kriging. Alternative integrated interpolationtechniques include standardized ordinary cokriging, collocated cokriging, and kriging withexternal drift. Application of these techniques to a specific exploration area in interpolatinggravity measurements (primary data) using weakly correlated aeromagnetics (secondary data)suggests that when gravity is well sampled, all techniques generate similar results. However,when gravity is undersampled, the secondary data can contribute substantially to identifyinggeophysical anomalies. Considering the high cost of geophysical data collection, this observationcan make geophysical data collection more efficient and cost effective. The case studyshows how, in the absence of a strong correlation, cokriging varieties tend to produce mapssimilar to those generated by traditional techniques. Kriging with external drift is shown togenerate a gravity map reproducing all gravity anomalies. The technique produces excellentresults when features identified in the secondary data need to be reflected in the map of theprimary data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010161813931
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  • 2
    Electronic Resource
    Electronic Resource
    Sources, sinks, and fluxes of nutrients (N + P) in a small highly modified urban estuary in southern California (2000)
    Springer
    Urban ecosystems 4 (2000), S. 125-144 
    Details
    ISSN: 1573-1642
    Keywords: nitrogen ; phosphorus ; macroalgae ; estuary ; anthropogenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Our objective was to begin to investigate sources, sinks, and flux rates of nitrogen (N) and phosphorus (P) in Famosa Slough, a small (12 ha) highly modified urban estuary in San Diego, California, U.S.A. The hydrology of Famosa Slough has been modified by culverts that dampen tidal influence and seasonal runoff from two urban watersheds, each of which has been implicated as a nutrient source that generates nuisance algal blooms. In 1995 and 1996, the ranges of nutrients measured in the water column were extremely wide; upper values exceeded those in other estuaries identified as eutrophic. Average dissolved inorganic nitrogen ranged from 2 to 250 μM, while dissolved inorganic phosphorus ranged from 〈1 to 15 μM. Nutrient content of the water changed rapidly both spatially and temporally depending on the tides and rainfall. While tidal water dominated this system, especially in the dry season, our results indicate that Famosa Slough's small watershed, not the larger watershed of the San Diego River, was the major source of nutrients during rainfall. Sediment nutrients were also high (∼3 mg N g dry wt−1 and 0.600 mg P g dry wt−1). Short-term flux studies suggest that the large accumulations of opportunistic green macroalgae commonly found in this estuary, and possibly the sediments, may act as a large and rapid sink for nutrients during times of high nutrient supply. We suggest that small, shallow estuaries in urban settings may have more complex and rapid nutrient dynamics than those found in larger systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011359311384
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  • 3
    Electronic Resource
    Electronic Resource
    Gradual Deformation and Iterative Calibration of Gaussian-Related Stochastic Models (2000)
    Springer
    Mathematical geology 32 (2000), S. 87-108 
    Details
    ISSN: 1573-8868
    Keywords: heterogeneity ; geostatistics ; optimization ; inversion ; nonlinearity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper describes a new method for gradually deforming realizations of Gaussian-related stochastic models while preserving their spatial variability. This method consists in building a stochastic process whose state space is the ensemble of the realizations of a spatial stochastic model. In particular, a stochastic process, built by combining independent Gaussian random functions, is proposed to perform the gradual deformation of realizations. Then, the gradual deformation algorithm is coupled with an optimization algorithm to calibrate realizations of stochastic models to nonlinear data. The method is applied to calibrate a continuous and a discrete synthetic permeability fields to well-test pressure data. The examples illustrate the efficiency of the proposed method. Furthermore, we present some extensions of this method (multidimensional gradual deformation, gradual deformation with respect to structural parameters, and local gradual deformation) that are useful in practice. Although the method described in this paper is operational only in the Gaussian framework (e.g., lognormal model, truncated Gaussian model, etc.), the idea of gradually deforming realizations through a stochastic process remains general and therefore promising even for calibrating non-Gaussian models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007506918588
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  • 4
    Electronic Resource
    Electronic Resource
    Blending-Based Stochastic Simulator (2000)
    Springer
    Mathematical geology 32 (2000), S. 367-379 
    Details
    ISSN: 1573-8868
    Keywords: random functions ; simulation ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper presents a new method of constructing random functions whose realizations can be evaluated efficiently. The basic idea is to “blend,” both stochastically and linearly, a limited set of independent initial realizations previously generated by any chosen simulation method. The blending stochastic coefficients are determined in such a way that the new random function so generated has the same mean and covariance functions as the random function used for generating the initial realizations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007590012189
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  • 5
    Electronic Resource
    Electronic Resource
    A Method to Estimate Length Distributions from Outcrop Data (2000)
    Springer
    Mathematical geology 32 (2000), S. 389-419 
    Details
    ISSN: 1573-8868
    Keywords: shale ; geostatistics ; Bayes' theorem ; Frontier Formation ; Erlangian ; tide-influenced delta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Dimensions of shales and other geologic bodies that affect fluid flow through reservoirs and aquifers are often estimated from analogous deposits exposed in outcrops. Shale lengths observed in outcrops are biased because the finite length of outcrops truncates longer shales and long shales tend to be overrepresented in the sample. Shale length distributions can be modeled using an Erlangian probability density function based on termination frequency. Termination frequency can be calculated from outcrop observations even if the shales are incompletely exposed. Termination frequency is unbiased regardless of underlying shale length distribution and outcrop size and shape. Complex length distributions can be represented by a weighted sum of Erlangian models, each with a distinct termination frequency. The proportions and termination frequencies of the component models can be estimated using Bayes' theorem. Subsamples of the outcrop area can be analyzed to quantify spatial trends in termination frequency and thus shale length. These methods can be applied to estimate length distributions of any geologic object exposed in outcrops or other spatially limited samples. In many cases estimated termination frequency is normally distributed, and its variance can be estimated using closed-form expressions. Shale length distributions for the Frewens Sandstone were modeled using one- and two-component Erlangian probability density functions. The Frewens Sandstone is a tide-influenced deltaic sandstone body within the Cretaceous-age Frontier Formation, exposed in central Wyoming, USA. Length observations and Erlangian models agree reasonably well. Because the models correct for the effects of shale truncation in limited outcrop exposures, predicted means and proportions of long shales are substantially greater than observed values. There is a vertical trend and pronounced vertical cyclicity in termination frequency, indicating that shales become shorter upward and intervals of longer and shorter shales alternate. Along strike, termination frequency decreases away from the sandstone-body axis, reflecting greater preserved shale lengths toward sandstone-body margins. No correlation was observed between distance along dip and termination frequency. Termination frequencies and histograms of shale length for adjacent, perpendicular walls are similar, indicating that there is no anisotropy in shale length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007510615051
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  • 6
    Electronic Resource
    Electronic Resource
    Nutrient losses in runoff from grasslandand shrubland habitats in southern New Mexico: II. Field plots (2000)
    Springer
    Biogeochemistry 49 (2000), S. 69-86 
    Details
    ISSN: 1573-515X
    Keywords: Bouteloua eriopoda ; Chihuahuan Desert ; desertification ; hydrology ; Larrea tridentata ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Losses of dissolved nutrients (N, P, K, Ca, Mg, Na,Cl, and SO4) in runoff were measured on grasslandand shrubland plots in the Chihuahuan desert ofsouthern New Mexico. Runoff began at a lowerthreshold of rainfall in shrublands than ingrasslands, and the runoff coefficient averaged 18.6%in shrubland plots over a 7-year period. In contrast,grassland plots lost 5.0 to 6.3% of incidentprecipitation in runoff during a 5.5-year period. Nutrient losses from shrubland plots were greater thanfrom grassland plots, with nitrogen losses averaging0.33 kg ha−1 yr−1 vs0.15 kg ha−1 yr−1, respectively, during a 3-year period. Thegreater nutrient losses in shrublands were due tohigher runoff, rather than higher nutrientconcentrations in runoff. In spite of these nutrientlosses in runoff, all plots showed net accumulationsof most elements due to inputs from atmosphericdeposition. Therefore, loss of soil nutrients byhillslope runoff cannot, by itself, account for thedepletion of soil fertility associated withdesertification in the Chihuahuan desert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006246126915
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  • 7
    Electronic Resource
    Electronic Resource
    Mercury speciation in natural waters: Measurement of dissolved gaseous mercury with a field analyzer (2000)
    Springer
    Biogeochemistry 48 (2000), S. 237-259 
    Details
    ISSN: 1573-515X
    Keywords: gaseous ; kinetics ; mercury ; methods ; speciation ; waters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Mercury evasion from water is commonly modeled using measurements of dissolved gaseous mercury (DGM). We developed a method using a recently available automated field-ready mercury vapor analyzer to rapidly measure the concentrations of DGM in surface waters. We summarize here results of laboratory tests of the method, field intercomparisons with a manual method, and selected data from recent sampling campaigns in Florida and Michigan. The method uses the 1.5 lpm flow of a Tekran® Model 2537A mercury analyzer to purge and analyze discrete water samples, generating near real time (5-min) data on DGM in samples and blanks. Application of the Tekran allowed for detailed analysis of DGM removal kinetics and short-term diel studies characterizing the influence of sunlight and precipitation on DGM production in surface waters. Gas removal kinetics for dozens of samples indicates a first-order rate constant, and supports a 20-min. purge time for surface water samples from Florida (40-min for Michigan samples). Blanks are measured during a second such purge. Our results indicate that DGMs determined by both automated and manual methods are generally comparable, and that DGM in Florida samples is unstable during storage (loss rate constant ∼0.1--0.2 h-1), probably due to oxidation. This suggests that rapid in-field analysis is preferred to storage with delayed analysis. Our data indicate that DGM at the Florida site is influenced by inputs of reactive Hg in rainwater, and by production of surface DGM during photoreduction of oxidized Hg in the water column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006228612872
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  • 8
    Electronic Resource
    Electronic Resource
    The Use of Fractal Geostatistics and Artificial Neural Networks for Carbonate Reservoir Characterization (2000)
    Springer
    Transport in porous media 41 (2000), S. 173-195 
    Details
    ISSN: 1573-1634
    Keywords: carbonate reservoir characterization ; geostatistics ; fractals ; artificial neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In this study, a carbonate oil reservoir located in the southeast part of Turkey was characterized by the use of kriging and the fractal geometry. The three-dimensional porosity and permeability distributions were generated by both aforementioned methods by using the wireline porosity logs and core plug permeability measurements taken from six wells of the field. Since classical regression (lognormal or polynomial) and geostatistical techniques (cross variograms) fail to estimate permeability from wireline log-porosity data, the use of artificial neural networks (ANNs) is proposed in this study to generate permeability data at uncored intervals of porosity logs. For both of the methods, kriging and fractal techniques, the validation of the estimated/simulated data with known wellbore data resulted with acceptable agreements, especially for porosity. Also the comparison of both methods at unsampled locations show better agreements for porosity than permeability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006725709303
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  • 9
    Electronic Resource
    Electronic Resource
    Application of kriging with external drift to estimate hydraulic conductivity from electrical-resistivity data in unconsolidated deposits near Montalto Uffugo, Italy (2000)
    Springer
    Hydrogeology journal 8 (2000), S. 356-367 
    Details
    ISSN: 1435-0157
    Keywords: Key words hydraulic properties ; heterogeneity ; geophysical methods ; geostatistics ; Italy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Dans le cadre de plusieurs études réalisées pour caractériser l'aquifère sur le site expérimental près de Montalto Uffugo (Italie), ce travail analyse la distribution spatiale de la conductivité hydraulique de formations non consolidées présentes dans cette région. La technique géostatistique du krigeage a été appliquée, avec une dérive externe, aux données de résistivitéélectrique et de conductivité hydraulique. La fiabilité de la méthode d'estimation a été testée en établissant un modèle, basé sur la méthode des cellules, qui simule l'écoulement souterrain, à partir des valeurs estimées de la conductivité hydraulique. Les résultats obtenus indiquent que cette méthode d'estimation présente un degré de fiabilité acceptable.
    Abstract: Resumen Dentro del marco de los estudios destinados a la caracterización del acuífero del campo experimental de aguas subterráneas cercano a Montalto Uffugo (Italia), el presente trabajo estima la distribución espacial de la conductividad hidráulica de los depósitos no consolidados subyacentes. El estudio se ha llevado a cabo mediante la técnica geoestadística del krigeado con deriva externa de los datos de resistividad eléctrica y de conductividad hidráulica. Se ha verificado la fiabilidad de la estimación mediante un modelo de simulación del flujo de aguas subterráneas, basado en el método de las celdas, que utiliza los valores estimados de la conductividad hidráulica. Los resultados obtenidos indican que el método de estimación empleado posee un grado de fiabilidad aceptable.
    Notes: Abstract  In the framework of various studies to characterize the aquifer at the groundwater experimental field near Montalto Uffugo, Italy, the present work estimates the spatial distribution of hydraulic conductivity of the unconsolidated deposits that underlie the area, by applying the geostatistical technique of kriging with external drift to electrical-resistivity and hydraulic-conductivity data. The reliability of the estimation method was tested by implementing a model, based on the method of cells, that simulates groundwater flow, with the estimated values of hydraulic conductivity. The results obtained indicate that the estimation method used has an acceptable degree of reliability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100400000083
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  • 10
    Electronic Resource
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    Contemporary carbon stocks of mineral forest soils in the Swiss Alps (2000)
    Springer
    Biogeochemistry 50 (2000), S. 111-136 
    Details
    ISSN: 1573-515X
    Keywords: carbon sequestration ; geostatistics ; mountain forest soils ; national assessment ; soil organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Soil organic carbon (SOC) has been identified as the main globalterrestrial carbon reservoir, but considerable uncertainty remains as toregional SOC variability and the distribution of C between vegetationand soil. We used gridded forest soil data (8–km × 8–km)representative of Swiss forests in terms of climate and forest typedistribution to analyse spatial patterns of mineral SOC stocks alonggradients in the European Alps for the year 1993. At stand level, meanSOC stocks of 98 t C ha−1 (N = 168,coefficient of variation: 70%) were obtained for the entiremineral soil profile, 76 t C ha−1 (N =137, CV: 50%) in 0–30 cm topsoil, and 62 t Cha−1 (N = 156, CV: 46%) in0–20 cm topsoil. Extrapolating to national scale, we calculatedcontemporary SOC stocks of 110 Tg C (entire mineral soil, standarderror: 6 Tg C), 87 Tg C (0–30 cm topsoil, standarderror: 3.5 Tg C) and 70 Tg C (0–20 cm topsoil, standarderror: 2.5 Tg C) for mineral soils of accessible Swiss forests(1.1399 Mha). According to our estimate, the 0–20 cm layers ofmineral forest soils in Switzerland store about half of the Csequestered by forest trees (136 Tg C) and more than five times morethan organic horizons (13.2 Tg C). At stand level, regression analyses on the entire data set yielded nostrong climatic or topographic signature for forest SOC stocks in top(0–20 cm) and entire mineral soils across the Alps, despite thewide range of values of site parameters. Similarly, geostatisticalanalyses revealed no clear spatial trends for SOC in Switzerland at thescale of sampling. Using subsets, biotic, abiotic controls andcategorial variables (forest type, region) explained nearly 60%of the SOC variability in topsoil mineral layers (0–20 cm) forbroadleaf stands (N = 56), but only little of thevariability in needleleaf stands (N = 91,R 2 = 0.23 for topsoil layers). Considerable uncertainties remain in assessments of SOC stocks, due tounquantified errors in soil density and rock fraction, lack of data onwithin-site SOC variability and missing or poorly quantifiedenvironmental control parameters. Considering further spatial SOCvariability, replicate pointwise soil sampling at 8–km × 8–kmresolution without organic horizons will thus hardly allow to detectchanges in SOC stocks in strongly heterogeneous mountain landscapes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006320129112
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  • 11
    Electronic Resource
    Electronic Resource
    Dissolved organic nitrogen budgets for upland, forested ecosystems in New England (2000)
    Springer
    Biogeochemistry 49 (2000), S. 123-142 
    Details
    ISSN: 1573-515X
    Keywords: C:N ratio ; dissolved organic carbon ; dissolved organic nitrogen ; nitrogen ; stream chemistry ; watershed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Relatively high deposition ofnitrogen (N) in the northeastern United States hascaused concern because sites could become N saturated.In the past, mass-balance studies have been used tomonitor the N status of sites and to investigate theimpact of increased N deposition. Typically, theseefforts have focused on dissolved inorganic forms ofN (DIN = NH4-N + NO3-N) and have largelyignored dissolved organic nitrogen (DON) due todifficulties in its analysis. Recent advances in themeasurement of total dissolved nitrogen (TDN) havefacilitated measurement of DON as the residual of TDN− DIN. We calculated DON and DIN budgets using data onprecipitation and streamwater chemistry collected from9 forested watersheds at 4 sites in New England. TDNin precipitation was composed primarily of DIN. Netretention of TDN ranged from 62 to 89% (4.7 to 10 kghaminus 1 yrminus 1) of annual inputs. DON made up themajority of TDN in stream exports, suggesting thatinclusion of DON is critical to assessing N dynamicseven in areas with large anthropogenic inputs of DIN.Despite the dominance of DON in streamwater,precipitation inputs of DON were approximately equalto outputs. DON concentrations in streamwater did notappear significantly influenced by seasonal biologicalcontrols, but did increase with discharge on somewatersheds. Streamwater NO3-N was the onlyfraction of N that exhibited a seasonal pattern, withconcentrations increasing during the winter months andpeaking during snowmelt runoff. Concentrations ofNO3-N varied considerably among watersheds andare related to DOC:DON ratios in streamwater. AnnualDIN exports were negatively correlated withstreamwater DOC:DON ratios, indicating that theseratios might be a useful index of N status of uplandforests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006383731753
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  • 12
    Electronic Resource
    Electronic Resource
    Atmospheric deposition and watershed nitrogen export along an elevational gradient in the Catskill Mountains, New York (2000)
    Springer
    Biogeochemistry 50 (2000), S. 21-43 
    Details
    ISSN: 1573-515X
    Keywords: acid deposition ; atmospheric deposition ; nitrate ; nitrification ; nitrogen ; soil carbon ; soil chemistry ; stream water acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Cumulative effects of atmospheric N deposition mayincrease N export from watersheds and contribute tothe acidification of surface waters, but naturalfactors (such as forest productivity and soildrainage) that affect forest N cycling can alsocontrol watershed N export. To identify factors thatare related to stream-water export of N, elevationalgradients in atmospheric deposition and naturalprocesses were evaluated in a steep, first-orderwatershed in the Catskill Mountains of New York, from1991 to 1994. Atmospheric deposition of SO 4 2− , andprobably N, increased with increasing elevation withinthis watershed. Stream-water concentrations ofSO 4 2− increased with increasing elevationthroughout the year, whereas stream-waterconcentrations of NO 3 − decreased withincreasing elevation during the winter and springsnowmelt period, and showed no relation with elevationduring the growing season or the fall. Annual exportof N in stream water for the overall watershed equaled12% to 17% of the total atmospheric input on thebasis of two methods of estimation. This percentagedecreased with increasing elevation, from about 25%in the lowest subwatershed to 7% in the highestsubwatershed; a probable result of an upslope increasein the thickness of the surface organic horizon,attributable to an elevational gradient in temperaturethat slows decomposition rates at upper elevations. Balsam fir stands, more prevalent at upper elevationsthan lower elevations, may also affect the gradient ofsubwatershed N export by altering nitrification ratesin the soil. Variations in climate and vegetationmust be considered to determine how future trends inatmospheric deposition will effect watershed export ofnitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006332230890
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  • 13
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    Carbon, nitrogen and phosphorus cycling in rivermarginal wetlands; a model examination of landscapegeochemical flows (2000)
    Springer
    Biogeochemistry 50 (2000), S. 45-71 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; landscape geochemical flows ; model ; nitrogen ; phosphorus ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The importance of landscape geochemical flows wasinvestigated using a dynamic model simulating carbon,nitrogen and phosphorus cycling in riverine wetlands,which has been described in a previous paper. Thehydro-geomorphic unit (HGMU) concept was incorporatedin the model by defining a separate, completeunit-model for each unit (HGMU) within the wetland.These unit-models were connected by defining the flowsof nitrogen and phosphorus between them. These flows,also called landscape geochemical flows, usuallyconsist of flows of water containing N and P. The model was applied to a site at Kismeldon Meadows,in south-western England. This site consists of twounits, a slope and a floodplain, separated by a ditch,which catches most of the run off and shallowgroundwater flows from the slope. Only an estimated1% of the N and P that leaves the slope unit in thewater outflow reaches the floodplain unit; the rest iscaught in the system of ditches, which prevent thegeochemical flows taking their natural course. Toexamine the influence of this system of ditches, themodel was run for the same site, but without theditches. This is comparable to a situation of arestored site, where run off and shallow groundwaterflows containing nutrients, can freely get from theslope to the floodplain. The computer simulation experiment reconnecting theslope and floodplain showed that this (1) increasedthe nutrient input into the floodplain, causing ahigher biomass production, and (2) increased thewetness of the floodplain, causing slowerdecomposition, which together (3) led to a faster soilorganic matter accumulation in the floodplain.Nutrient inflows became relatively more importantcompared to atmospheric deposition, especially forphosphorus. By connecting the slope and the floodplainmore nitrogen and less phosphorus flowed into theriver.
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    URL: http://dx.doi.org/10.1023/A:1006360315792
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  • 14
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    Internal eutrophication in peat soils through competition between chloride and sulphate with phosphate for binding sites (2000)
    Springer
    Biogeochemistry 50 (2000), S. 183-194 
    Details
    ISSN: 1573-515X
    Keywords: chloride ; internal eutrophication ; nitrogen ; peat soil ; phosphorus ; phytometer ; sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Inputs of surface waters high in chloride and sulphateincreased the availability of nutrients in fenpeatlands. This `internal eutrophication' wasdemonstrated with test plants (`phytometers') andthrough water and soil analysis. Three experiments arepresented in which the level of chloride and/orsulphate was increased to 3 mmolc l−1. Inexperiment 1 chloride levels were increased from 0.5to 3 mmolc l−1 as CaCl2 or NaCl. Inexperiment 2 and 3 similar increased levels forchloride and sulphate (3 mmolc l−1; as NaCland Na2SO4) were used. The following resultswere found: (i) No differences in soil total-N and total-P werefound before and after the treatments in any of thethree experiments. (ii) Experiment 1 showed a significant increase inBio-Available P (BAP) in pots planted with Anthoxanthum odoratum as well as in bare pots for theNaCl and CaCl2 treatments. The plants in thesetreatments had taken up much more P. (iii) Experiment 2 showed an increase in soil BAPafter treatment with chloride and sulphate in potsplanted with Anthoxanthum odoratum. The chloridetreatment had no effect on plant biomass, whereas thesulphate treatment resulted in a reduction in rootbiomass and root N and P content. The shoots showedan increase in P content in the sulphate and chloridetreatments, while N content remained the same. (iv) In experiment 3, treatments with chloride andsulphate led to significantly increased biomass and Puptake of Anthoxanthum odoratum. Again, noeffects on N uptake were found. These experiments provide evidence for distinctlyincreased availability of phosphate in peat soils whenthese come into contact with water with evenmoderately increased sulphate or chloride levels.Surface water originating from the Rhine river, whichis enriched in chloride and sulphate, is oftensupplied to fen reserves in The Netherlands, tocompensate for water losses due to agriculturaldrainage in the region. The results of this study showthat phosphate availability to the vegetation may risedrastically, with detrimental effects on the speciesdensity and the occurrence of rare species in thevegetation. Hence, supply of this water should beavoided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006374018558
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  • 15
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    Using Bacterial Growth on Insects to Assess Nutrient Impacts in Streams (2000)
    Springer
    Environmental monitoring and assessment 63 (2000), S. 431-446 
    Details
    ISSN: 1573-2959
    Keywords: aquatic bacteria ; benthic macroinvertebrates ; bioindicator ; eutrophication ; nitrogen ; phosphorus ; stream pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A combination field and laboratorystudy was conducted to evaluate the ability of arecently developed bioindicator to detect detrimentalnutrient conditions in streams. The method utilizesbacterial growth on aquatic insects to determinenutrient impacts. Field investigations indicated thatelevated concentrations of nitrate and phosphate wereassociated with growth of filamentous bacteria oninsect body surfaces, and that there was a significantreduction in the density of major insect taxa in thenutrient-enriched stream reaches. Laboratoryinvestigations confirmed a strong linkage betweenbacterial growth and reduced survival of insects. Survival was examined for insects with bacterialinfestation ranging from 0% to greater than 50%coverage of the body surface. A threshold forcatastrophic mortality occurred at about 25% bodycoverage; there were few survivors above that amount. Based on these findings, the diagnostic endpoint forthe bioindicator is 25% body coverage by bacterialgrowth, a level that signifies major impacts and isalso easy to detect visually. This study providesadditional evidence that the insect-bacteriabioindicator is a reliable tool for assessing nutrientimpacts on stream macroinvertebrate communities. Thebioindicator should prove useful for identifyingnutrient-impacted sites as well as monitoring thesuccess of management actions to improve water quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006211929599
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    Input–Output Budgets of Major Ions for a Forested Watershed in Western Maryland (2000)
    Springer
    Water, air & soil pollution 119 (2000), S. 121-137 
    Details
    ISSN: 1573-2932
    Keywords: nitrogen ; wet deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We measured concentrations and fluxesof major ions in wet deposition, throughfall andstream water in a forested watershed on the AlleghenyPlateau of western Maryland to investigatecanopy-atmosphere interactions and to calculate input–output budgets. Wet deposition was dominated byH+, SO 4 2− , NO 3 − andNH 4 + ions. Hydrogen and SO 4 2− accounted for 70 and 58% of the total cation andanion equivalents, respectively. Annual wet depositionrates of SO 4 2− (0.56 keq ha−1 yr−1), NO 3 − (0.31 keq ha−1 yr −1)and NH 4 + (0.17 keq ha−1 yr −1)were at the high end of the range in wet depositionrates reported for other sites in the eastern UnitedStates. On an annual basis, the forest canopy consumed20% of the free acidity in incident precipitation,had no net effect on Na+ and NH 4 + deposition, and was a net source of K+,Ca2+, Mg2+, SO 4 2− andNO 3 − ; 1.5 to 22 times greater than the wetdeposition rates. On an annual basis, the watershed ofthe unnamed tributary to Herrington Creek (HCWS)retained essentially all of the throughfall H+ andNH 4 + inputs, 35% of the throughfall K+input and 62% of the throughfall NO 3 − input. In contrast, HCWS was a net source ofSO 4 2− , Cl−, Ca2+, Mg2+ andNa+; export rates were 2 to 5 times greater thanthroughfall inputs. Sulfate was the dominant anionassociated with cation leaching, accounting for 78%of the total anion export of 1.8 keq ha−1 yr −1 in 1996–1997.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005113426448
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    Variability in Contamination by Heavy Metals: Sampling Implications (2000)
    Springer
    Water, air & soil pollution 120 (2000), S. 29-45 
    Details
    ISSN: 1573-2932
    Keywords: geostatistics ; heavy metals ; samplingdesign ; soil contamination ; spatial variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The choice of a sampling design forassessing soil contamination is a key issue. The leveland spatial pattern of contaminants needs to be takeninto account by those buying, selling or developingsuch land. This paper evaluates sampling design andsize in order to provide satisfactory and efficientestimates of contamination levels. Geostatisticalmethods are used to quantify the spatial dependence ofheavy metals. Semivariance is calculated forlog-transformed data to minimise the effects ofextreme outliers. Several models at different samplingstages are presented for characterising spatialpattern of heavy metals at the investigated site.Variogram models are calculated for a range of samplesizes. The results are assessed by a jack-knifingtechnique and then used for block kriging. The overallconclusion is that a sample size of 50 to 60 isoptimal for characterising variability incontamination levels at an old industrial site of 6.25 ha.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005261522465
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    Nitrogen and Phosphorus Levels in Sediments from Tropical Catatumbo River (Venezuela) (2000)
    Springer
    Water, air & soil pollution 117 (2000), S. 27-37 
    Details
    ISSN: 1573-2932
    Keywords: eutrophication ; nitrogen ; phosphorus ; river ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen (N) and phosphorus (P) concentrations were determined in sediment samples along the bed of Catatumbo river in both Colombian and Venezuelan territories until the river outlet in Maracaibo lake. Total phosphorus was determined by digestion with HCl followed by analysis using the ascorbic acid method and total nitrogen was done using the standard microkjeldahl method plus nitrate-nitrite. Ammonium, orthophosphate and nitrate were determined using standard methods after extraction steps. The mean concentrations along the river bed were found in an interval of 0.035 and 1.492 mg g-1 dry sed. for nitrogen and 0.027 and 1.039 mg g-1 dry sed. for phosphorus at 95% confidence level. The mean molar ratio N/P in the river bed was 4.42 and 3.46 for river outlet zones in the lake, which indicates that nitrogen is the limiting nutrient. For comparison with previous results of lake sediments from sites near the river outlet it was concluded that Catatumbo river is a significant source of nutrients to the Maracaibo Lake system because sediment nutrients concentrations from Catatumbo river were higher than the ones in Maracaibo Lake. Statistic studies showed significant differences between countries, zones and similar behaviour in the river bed as related to the affluent rivers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005189710803
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    Analysis of Nitrogen Dynamics in the Lye Brook Wilderness Area, Vermont, USA (2000)
    Springer
    Water, air & soil pollution 122 (2000), S. 63-75 
    Details
    ISSN: 1573-2932
    Keywords: nitrification ; nitrogen ; nitrogen mineralization ; soil water ; stream chemistry ; wilderness area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen (N) deposition and its impact on terrestrial and aquatic ecosystems is a concern facing federal land managers at the Lye Brook Wilderness in Vermont and other protected aras throughout the northeastern United States. In this study, we compared N production in soils with N concentrations and outputs in leachates to determine how forest cover types differ in regulating N losses. Also, precipitation inputs and modeled estimates of streamwater outputs were used to calculate a watershed N budget. Most ammonium and nitrate were produced in organic soils with deciduous cover. Softwood stands had low net nitrification rates and minimal N leaching. A comparison of watershed inputs and outputs showed a net gain in total dissolved N (5.5 kg ha-1 yr-1) due to an accumulation of dissolved inorganic N. The Lye Brook Wilderness ecosystem has N budgets similar to other forested ecosystems in the region, and appears to be assimilating the accumulating N. However seasonal losses of nitrate observed in mineral soils and streamwater may be early warnings of the initial stages of N saturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005258814565
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  • 20
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    Treatment of Septic Effluent for Fecal Coliform and Nitrogen in Coarse-textured Soils: Use of Soil-only and Sand Filter Systems (2000)
    Springer
    Water, air & soil pollution 124 (2000), S. 205-215 
    Details
    ISSN: 1573-2932
    Keywords: on-site treatment ; fecal coliform bacteria ; nitrate leaching ; nitrogen ; on-site treatment ; septic effluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Groundwater effluent sample collectors(zero-tension lysimeters) were installed directlybelow the drainfields of three residential onsitetreatment systems in the Clover/Chambers Creek aquiferregion of Pierce County near Tacoma, WA. The use of asplit effluent delivery system from the septic tank,where half the effluent was delivered under pressureto a normal native soil-only filter system and halfwas delivered to a sand filter system, allowed thedirect comparison of the two commonly-utilized septicsystems for treatment levels. Septic tank effluent(from the septic tank) and percolating water (between0.3 and 0.9 m beneath the effluent distributionlines) was collected between May 1991 and April 1994on 30 occasions. Samples were analyzed for fecalcoliform bacteria, nitrate, nitrite, ammonium andtotal reduced (Kjeldahl) nitrogen. Results of thisstudy indicate that the use of sand filters greatlyincreased removal of fecal coliform bacteria and totalnitrogen. Soil-only filter systems had an average of91% removal of fecal coliforms and 47%of total N; whereas sand filter systems had an averageof 99.8% removal of fecal coliforms and 80% of total N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005298932244
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    Spatial and Temporal Patterns of Chloride Deposition in Southern Sweden (2000)
    Springer
    Water, air & soil pollution 124 (2000), S. 345-369 
    Details
    ISSN: 1573-2932
    Keywords: chloride ; climate ; deposition ; geostatistics ; kriging ; pattern ; Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Monthly bulk deposition of chloride at 49 stations in Southern Sweden between 1989 and 1995 was used to produce quarterly and annual deposition maps through ordinary block kriging. Generally, deposition decreases from the west coast and eastward and displays a large annual variation, governed by the frequency and intensity of midlatitude cyclones. The 1st quarter dominates the temporal pattern all years except 1992. The 4th quarter is the second most important and the 2nd and 3rd quarters have generallylow deposition. The spatial deposition maximum was often displaced from the west coast to the western fringe of the South Swedish highland, due to orographic enhancement of precipitation. On the western rise of the highland, deposition almost entirely co-variates with precipitation. On the west coast and in the eastern part of Southern Sweden, thetemporal pattern is a more complex result of precipitation and frequency of strong westerlies. Comparing the quarterly total dataset with precipitation and frequency of westerly gales shows that both the 3rd and 4th quarters have higher mean precipitation than the 1st quarter, but lower deposition, while the second quarter has substantially lower precipitation but almost equal deposition to the 3rd quarter. The frequency of westerly gales shows a clearer, linear relationship to quarterly deposition. The 1st quarter has the highest variability in deposition and precipitation as well as in frequency of westerly gales. The importance of single highlysalt laden cyclones to the annual deposition is obvious in the 1st quarter of 1993. Changes in cyclone activity due to climate change is therefore of vital importance for the chemical characteristics of the midlatitude atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005261417707
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    The Replacement Value of Wetlands in Sweden (2000)
    Springer
    Environmental and resource economics 16 (2000), S. 347-362 
    Details
    ISSN: 1573-1502
    Keywords: cost-effectiveness ; nitrogen ; nonpoint ; policy ; value ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Wetlands, in Sweden and elsewhere, have been suggestedas effective and low-cost sinks for agriculturalpollution. This paper estimates the value of usingwetlands for abatement of agricultural nitrogen loadon the Baltic Sea. A replacement value of wetlands isestimated for Sweden. The replacement value is definedand estimated as the difference between twocost-effective reductions of agricultural nitrogenpollution: one that uses wetlands for nitrogenabatement, and one that does not. It is shown that theuse of wetlands as nitrogen sinks can reduce the totalabatement costs of nitrogen emissions by 30% forSwedish agricultural sources of nitrogen pollution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008316619355
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    Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 41-51 
    Details
    ISSN: 1572-8900
    Keywords: Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are α- and β-(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.
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    URL: http://dx.doi.org/10.1023/A:1021894102937
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    Comparison of Point Estimation Techniques in the Spatial Analysis of Radium-226, Radium-228 and Potassium-40 in Soil (1999)
    Springer
    Environmental monitoring and assessment 59 (1999), S. 191-209 
    Details
    ISSN: 1573-2959
    Keywords: estimation ; geostatistics ; interpolation ; radionuclides ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Many environmental surveys require the implementation of estimation techniques to determine the spatial distribution of the variable being investigated. Traditional methods of interpolation and estimation, for example, inverse distance squared and triangulation often ignore features of the data set such as anisotropy which may have a significant impact on the quality of the estimates produced. Geostatistical techniques may offer an improved method of estimation by modelling the spatial continuity of the variable using semi-variogram analysis. The theoretical model fitted to the semi-variogram is then used in the assignation of weighting factors to the samples surrounding the location to be estimated. This paper outlines the results of a comparison between three common estimation methods, polygonal, triangulation and inverse distance squared and a geostatistical method, in the estimation of soil radionuclide activities. The geostatistical estimation method known as kriging performed best over a range of parameters used to test the performance of the methods. Kriging exhibited the best correlation between actual and estimated values, the narrowest error distribution and the lowest overall estimation error. Polygonal estimation was best at reproducing the data set distribution. Conditional bias was evident in all the methods, low values being over-estimated and high values being under-estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006141008027
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    An Experimental Comparison of Ordinary and Universal Kriging and Inverse Distance Weighting (1999)
    Springer
    Mathematical geology 31 (1999), S. 375-390 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; spatial interpolation ; spatial pattern ; surface-fitting algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A factorial, computational experiment was conducted to compare the spatial interpolation accuracy of ordinary and universal kriging and two types of inverse squared-distance weighting. The experiment considered, in addition to these four interpolation methods, the effects of four data and sampling characteristics: surface type, sampling pattern, noise level, and strength of small-scale spatial correlation. Interpolation accuracy was measured by the natural logarithm of the mean squared interpolation error. Main effects of all five factors, all two-factor interactions, and several three-factor interactions were highly statistically significant. Among numerous findings, the most striking was that the two kriging methods were substantially superior to the inverse distance weighting methods over all levels of surface type, sampling pattern, noise, and correlation.
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    URL: http://dx.doi.org/10.1023/A:1007586507433
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    Simulation of Non-Gaussian Transmissivity Fields Honoring Piezometric Data and Integrating Soft and Secondary Information (1999)
    Springer
    Mathematical geology 31 (1999), S. 907-927 
    Details
    ISSN: 1573-8868
    Keywords: conditional probabilities method ; self-calibrated method ; stochastic inversion ; probabilistic assessment ; geostatistics ; stochastic hydrology ; probability fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The conditional probabilities (CP) method implements a new procedure for the generation of transmissivity fields conditional to piezometric head data capable to sample nonmulti-Gaussian random functions and to integrate soft and secondary information. The CP method combines the advantages of the self-calibrated (SC) method with probability fields to circumvent some of the drawbacks of the SC method—namely, its difficulty to integrate soft and secondary information or to generate non-Gaussian fields. The SC method is based on the perturbation of a seed transmissivity field already conditional to transmissivity and secondary data, with the perturbation being function of the transmissivity variogram. The CP method is also based on the perturbation of a seed field; however, the perturbation is made function of the full transmissivity bivariate distribution and of the correlation to the secondary data. The two methods are applied to a sample of an exhaustive non-Gaussian data set of natural origin to demonstrate the interest of using a simulation method that is capable to model the spatial patterns of transmissivity variability beyond the variogram. A comparison of the probabilistic predictions of convective transport derived from a Monte Carlo exercise using both methods demonstrates the superiority of the CP method when the underlying spatial variability is non-Gaussian.
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    URL: http://dx.doi.org/10.1023/A:1007580902175
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    Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment (1999)
    Springer
    Journal of oceanography 55 (1999), S. 1-11 
    Details
    ISSN: 1573-868X
    Keywords: Osaka Bay ; sediment ; carbon ; nitrogen ; organic matter ; stable isotope ratio ; terrestrial organic matter ; TOC ; POC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Carbon and nitrogen stable isotope ratios (δ13C and δ15N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The δ13C and δ15N of surface sediments in the estuary of the Yodo River were less than −23‰ and 5‰ respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving δ13C of about −20‰ and δ15N about 6‰). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.
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    URL: http://dx.doi.org/10.1023/A:1007850003262
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    Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries? An exploration with a simulation model (1999)
    Springer
    Biogeochemistry 46 (1999), S. 203-231 
    Details
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; Zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by Zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high Zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a Zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
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    URL: http://dx.doi.org/10.1007/BF01007580
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    Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests (1999)
    Springer
    Biogeochemistry 46 (1999), S. 45-65 
    Details
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more 15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in 15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006100128782
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006156213761
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    Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries? An exploration with a simulation model (1999)
    Springer
    Biogeochemistry 46 (1999), S. 203-231 
    Details
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
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    URL: http://dx.doi.org/10.1023/A:1006189121030
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    Electronic Resource
    Bayesian Inference of Spatial Covariance Parameters (1999)
    Springer
    Mathematical geology 31 (1999), S. 47-65 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; prior distribution ; likelihood function ; posterior distribution ; variogram ; covariance ; range
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract This paper shows the application of the Bayesian inference approach in estimating spatial covariance parameters. This methodology is particularly valuable where the number of experimental data is small, as occurs frequently in modeling reservoirs in petroleum engineering or when dealing with hydrodynamic variables in groundwater hydrology. There are two main advantages of Bayesian estimation: firstly that the complete distribution of the parameters is estimated and, from this distribution, it is a straightforward procedure to obtain point estimates, confidence regions, and interval estimates; secondly, all the prior information about the parameters (information available before the data are collected) is included in the inference procedure through their prior distribution. The results obtained from simulation studies are discussed.
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    URL: http://dx.doi.org/10.1023/A:1007541330206
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    Geostatistical Space–Time Models: A Review (1999)
    Springer
    Mathematical geology 31 (1999), S. 651-684 
    Details
    ISSN: 1573-8868
    Keywords: space–time models ; geostatistics ; time series ; trend models ; stochastic simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Geostatistical space–time models are used increasingly for addressing environmental problems, such as monitoring acid deposition or global warming, and forecasting precipitation or stream flow. Each discipline approaches the problem of joint space–time modeling from its own perspective, a fact leading to a significant amount of overlapping models and, possibly, confusion. This paper attempts an annotated survey of models proposed in the literature, stating contributions and pinpointing shortcomings. Stochastic models that extend spatial statistics (geostatistics) to include the additional time dimension are presented with a common notation to facilitate comparison. Two conceptual viewpoints are distinguished: (1) approaches involving a single spatiotemporal random function model, and (2) approaches involving vectors of space random functions or vectors of time series. Links between these two viewpoints are then revealed; advantages and shortcomings are highlighted. Inference from space–time data is revisited, and assessment of joint space–time uncertainty via stochastic imaging is suggested.
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    URL: http://dx.doi.org/10.1023/A:1007528426688
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  • 34
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    URL: http://dx.doi.org/10.1007/BF00993000
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1× 104 kg nitrogen and 3.91×104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7×104 kg (676 kg/ha) nitrogen and 3.88×104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55×104 kg nitrogen and 0.40×104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    URL: http://dx.doi.org/10.1007/BF00992870
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  • 36
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    Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 21-34 
    Details
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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    URL: http://dx.doi.org/10.1007/BF00992871
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  • 37
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    URL: http://dx.doi.org/10.1023/A:1006076405557
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  • 38
    Electronic Resource
    Electronic Resource
    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 × 104 kg nitrogen and 3.91 × 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 × 104 kg (676 kg/ha) nitrogen and 3.88 × 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 × 104 kg nitrogen and 0.40 × 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    URL: http://dx.doi.org/10.1023/A:1006073408623
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    The fate of NH4NO3 added toSphagnum magettanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m−2 yr−1 were made toSphagnum magellanicurn cores at two-week intervalsin situ at four sites across Europe, i.e. Lakkasuo (Finland). Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N∶P ratio 68) and greatest in Moidach More (N∶P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4 + in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3 − were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition bySphagnum mosses.
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    URL: http://dx.doi.org/10.1007/BF00992874
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    Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests (1999)
    Springer
    Biogeochemistry 46 (1999), S. 45-65 
    Details
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
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    URL: http://dx.doi.org/10.1007/BF01007573
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  • 41
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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    URL: http://dx.doi.org/10.1007/BF01007576
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    Effect of soil characteristics on sequential reduction and methane production in sixteen rice paddy soils from China, the Philippines, and Italy (1999)
    Springer
    Biogeochemistry 47 (1999), S. 267-293 
    Details
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 - , SO 4 2 , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4 and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9 μmol d-1 g-1 dry soil. Methane production started after 2 to 87 days and became constant after about 38--68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08 μmol d-1 g-1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30 μmol d-1 g-1 and 0.02 and 0.28 μmol d-1 g-1, respectively. Within the 120 d of anaerobic incubation only 6--17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61--100% CO2, 〈0.1--35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r = 0.891) and total CH4 produced (r = 0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
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    URL: http://dx.doi.org/10.1023/A:1006186420644
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    Effect of soil characteristics on sequential reduction and methane production in sixteen rice paddy soils from China, the Philippines, and Italy (1999)
    Springer
    Biogeochemistry 47 (1999), S. 269-295 
    Details
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 − , SO 4 2− , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4. and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9μmol d−1 g−1 dry soil. Methane production started after 2 to 87 days and became constant after about 38–68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08μmol d−1 g−1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30μmol d−1 g−1 and 0.02 and 0.28μmol d−1 g−1, respectively. Within the 120 d of anaerobic incubation only 6–17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61–100% CO2, 〈0.1–35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r=0.891) and total CH4 produced (r =0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
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    URL: http://dx.doi.org/10.1007/BF00992910
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    Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils (1999)
    Springer
    Biodegradation 10 (1999), S. 43-50 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; nitrogen ; nutrients ; phenanthrene ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation. To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus. Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus. Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added. The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils. To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.
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    Absolute Rate Coefficients for the Gas-Phase Reactions of NO3 Radical with a Series of Monoterpenes at T = 298 to 433 K (1999)
    Springer
    Journal of atmospheric chemistry 33 (1999), S. 265-282 
    Details
    ISSN: 1573-0662
    Keywords: atmosphere ; kinetics ; nitrate radical ; monoterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The aim of this work is to study the reactivity of some naturally emitted terpenes, 2-carene, sabinene, myrcene, α-phellandrene, d-limonene, terpinolene and γ-terpinene, towards NO3 radical to evaluate the importance of these reactions in the atmosphere and their atmospheric impact. The experiments with these monoterpenes have been carried out under second-order kinetic conditions over the range of temperature 298–433 K, using a discharge flow system and monitoring the NO3 radical by Laser Induced Fluorescence (LIF). This work is the first temperature dependence study for the reactions of the nitrate radical with the above-mentioned monoterpenes. The measured rate constants at 298 K for the reaction of NO3 with such terpenes are as follows: 2-carene, 16.6 ± 1.8, sabinene 10.7 ± 1.6, myrcene 12.8 ± 1.1, α-phellandrene 42 ± 10, d-limonene 9.4 ± 0.9, terpinolene 52 ± 9 and γ-terpinene 24 ± 7, in units of 10-12 cm3 molecule-1 s-1. The proposed Arrhenius expressions, for the reactions of NO3 with 2-carene, sabinene, myrcene and α-phellandrene are, respectively k1 = (1.4 ± 0.7) × 10-12 exp[(741 ± 190/T)] (cm3 molecule-1 s-1), k2=(2.3 ± 1.3) × 10-10 exp[−(940 ± 200/T)] (cm3 molecule-1 s-1), k3 = (2.2 ± 0.2) × 10-12 exp[(523 ± 35/T)] (cm3 molecule1 s-1) and k4 = (1.9 ± 1.3) × 10-9 exp[−(1158 ± 270/T)] (cm3 molecule-1 s-1). A decrease in the rate constants when raising the temperature has also been found for the reaction of d-limonene with NO3 while an increase in the rate constant with temperature has been observed for the reactions of terpinolene and γ-terpinene with NO3. Tropospheric half-lives for these terpenes have been calculated at night and during the day for typical NO3 and OH concentrations showing that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with NO3 radical can be an important, if not dominant, loss process for these naturally emitted organics and for NO3 radicals.
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    URL: http://dx.doi.org/10.1023/A:1006178530211
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    Laboratory Kinetic Studies of the Reactions of Cl Atoms with Species of Biogenic Origin: δ3-Carene, Isoprene, Methacrolein and Methyl Vinyl Ketone (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 163-170 
    Details
    ISSN: 1573-0662
    Keywords: δ3-carene ; chlorine atoms ; isoprene ; kinetics ; methacrolein and methyl vinyl ketone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The rate coefficients for the reaction between atomic chlorine and a number of naturally occurring species have been measured at ambient temperature and atmospheric pressure using the relative rate technique. The values obtained were (4.0 ± 0.8) × 10-10, (2.1 ± 0.5) × 10-10, (3.2 ± 0.5) × 10-10, and (4.9 ± 0.5) × 10-10 cm3 molecule-1 s-1, for reactions with isoprene, methyl vinyl ketone, methacrolein and δ3-carene, respectively. The value obtained for isoprene compares favourably with previously reported values. No values have been reported to date for the rate constants of the other reactions.
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    URL: http://dx.doi.org/10.1023/A:1006214423298
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    Modelling the growth of a methanotrophic biofilm: Estimation of parameters and variability (1999)
    Springer
    Biodegradation 10 (1999), S. 177-191 
    Details
    ISSN: 1572-9729
    Keywords: AQUASIM ; biodegradation ; biofilm ; growth ; kinetics ; methane ; modelling ; nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This article discusses the growth of methanotrophic biofilms. Several independent biofilm growths scenarios involving different inocula were examined. Biofilm growth, substrate removal and product formation were monitored throughout the experiments. Based on the oxygen consumption it was concluded that heterotrophs and nitrifiers co-existed with methanotrophs in the biofilm. Heterotrophic biomass grew on soluble polymers formed by the hydrolysis of dead biomass entrapped in the biofilm. Nitrifier populations developed because of the presence of ammonia in the mineral medium. Based on these experimental results, the computer program AQUASIM was used to develop a biological model involving methanotrophs, heterotrophs and nitrifiers. The modelling of six independent growth experiments showed that stoichiometric and kinetic parameters were within the same order of magnitude. Parameter estimation yielded an average maximum growth rate for methanotrophs, μm, of 1.5 ± 0.5 d−1, at 20 °C, a decay rate, bm, of 0.24 ± 0.1 d−1, a half saturation constant, $${\text{K}}_{{\text{S(CH}}_{\text{4}} {\text{)}}} $$ , of 0.06 ± 0.05 mg CH4/L, and a yield coefficient, $$Y_{CH_4 } $$ , of 0.57 ±: 0.04 g X/g CH4. In addition, a sensitivity analysis was performed on this model. It indicated that the most influential parameters were those related to the biofilm (i.e. density; solid-volume fraction; thickness). This suggests that in order to improve the model, further research regarding the biofilm structure and composition is needed.
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    URL: http://dx.doi.org/10.1023/A:1008317906069
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    The fate of NH4NO3 added to Sphagnum magellanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
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    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m-2 yr-1 were made to Sphagnum magellanicum cores at two-week intervals in situ at four sites across Europe, i.e. Lakkasuo (Finland), Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N:P ratio 68) and greatest in Moidach More (N:P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4+ in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3- were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition by Sphagnum mosses.
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    URL: http://dx.doi.org/10.1023/A:1006133828518
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    Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 21-34 
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    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/l) and lowest in bare plots in the shrubland (0.55 mg/l). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands – consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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    URL: http://dx.doi.org/10.1023/A:1006020831706
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    Rubidium and Cesium Kinetics and Tissue Distributions in Channel Catfish (Ictalurus punctatus) (1999)
    Springer
    Ecotoxicology 8 (1999), S. 287-300 
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    ISSN: 1573-3017
    Keywords: rubidium ; cesium ; kinetics ; clearance-volume model ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We used a two-compartment, clearance volume-based model to examine rubidium and cesium pharmacokinetics in channel catfish (Ictalurus punctatus) after intravascular administration. We compared the apparent volumes of distribution in the central and peripheral compartments and the intercompartmental and whole-body clearances of both metals at 20.0 °C and 27.5 °C. Biological half-times of Rb were 15 to 16 d at both temperatures, but Cs biological half-times averaged 101 d and 85 d at 20.0 °C and 27.5 °C, respectively (5 to 7 times longer than those of Rb in the same individual). Both the intercompartmental and total body clearances of Rb were also 6 to 7 times greater than those of Cs. The apparent volumes of distribution for Rb in the central compartments were twice those of Cs and remained constant with temperature. The apparent volumes of distribution of both elements in peripheral compartments were large compared with their corresponding central compartments, and decreased by a similar extent with increased temperature. Cesium tissue to blood ratios were greatest for white muscle, with more than 85% of the Cs present in this tissue. Partitioning of Cs in peripheral tissues apparently decreased with increased temperature conditions. Our results indicate that application of pharmacokinetic modeling techniques can enhance studies of radionuclide kinetics by helping to identify rate-limiting processes within individuals that may control uptake and elimination.
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    URL: http://dx.doi.org/10.1023/A:1008981216690
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    Estimation of riverine loads of nitrogen and phosphorus to the Baltic Sea, 1970–1993 (1999)
    Springer
    Environmental monitoring and assessment 58 (1999), S. 173-200 
    Details
    ISSN: 1573-2959
    Keywords: Baltic Sea ; nitrogen ; phosphorous ; riverine load ; timeseries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This article presents the results of the first critical examination of time series of riverine nutrient-load data for the entire Baltic Sea drainage area. Water quality data collected by or for the different national environmental agencies were compiled and analysed statistically to identify and remove inconsistent or obviously incorrect observations. Moreover, sampling tours were undertaken to acquire additional information about the present nutrient concentrations in the largest rivers in the study area. Gaps in the time series of approved data were then filled in by employing statistical interpolation and extrapolation methods. Thereafter, the concentration and runoff data were combined to obtain estimates of monthly nutrient loads for the time period 1970–93. The results of the calculations showed that although there had been substantial changes in land use, atmospheric deposition and wastewater treatment in many parts of the study area, the total riverine loads of nitrogen (N) and phosphorus (P) to the Baltic Sea have been fairly constant since 1980, and most likely also since 1970. Moreover, the interannual variation was clearly correlated to the runoff. The mean annual loads for the time period 1980–93 were found to be about 825 000 tonnes N and 41 000 tonnes P, respectively. This implies that (i) several other investigators have strongly underestimated the riverine loads of nutrients, especially the nitrogen, and that (ii) the riverine loads by far exceed the input to the Baltic Sea from other sources, {i.e.} atmospheric deposition, direct emissions from cities and industries along the Baltic Sea coast and nitrogen fixation by marine algae.
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    URL: http://dx.doi.org/10.1023/A:1006073015871
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    Reducing Ammonia Losses by Adding FeCl3 During Composting of Sewage Sludge (1999)
    Springer
    Water, air & soil pollution 112 (1999), S. 229-239 
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    ISSN: 1573-2932
    Keywords: ammonia ; composting ; iron chloride ; nitrogen ; sewage sludge ; volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The release of ammonia nitrogen during composting of sewage sludge mixed with a lignocellulosic bulking agent leads to a reduction in the agronomic value of the final compost and to harmful effects on the environment. We propose adding a cheap salt FeCl3 which can be used without special precaution to reduce ammonia losses by decreasing pH conditions. An in-vessel co-composting experiment was conducted in a large reactor (100 L) in which FeCl3 was added to sludge mixed with a bulking agent (pine shavings and sawdust) and compared with a control mixture without FeCl3. Temperature, oxygen consumption and pH were monitored throughout the composting of both mixtures. The final balance of organic matter, organic and inorganic nitrogen permitted to conclude that the addition of FeCl3 reduced nitrogen loss (by a factor of 2.4 in relation to the control) and increased mineralisation of the organic nitrogen by 1.6.
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    Nitrogen Dynamics in Forest Soils after Municipal Sludge Additions (1999)
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    Water, air & soil pollution 112 (1999), S. 259-278 
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    ISSN: 1573-2932
    Keywords: forest ; municipal sludge ; nitrogen ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen dynamics were assessed for a forested site in southern New Hampshire during the first and second growing seasons after surface application of an aerobically-digested, limed, liquid municipal sludge. Sludge was applied in June 1989, at 3.3, 6.9, and 14.5 M ha-1 (or 199, 396, and 740 kg TKN ha-1). Elevated net N mineralization (in situ buried bags) occurred in the organic and upper mineral soil horizons during the first two months after sludge application, but was similar to control levels thereafter. Net N mineralization was negligible at 30 and 60 cm soil depths. Foliar N concentration increased with sludge loading rates. Concentrations of NH4+ and NO3- in soil leachate were low, except in early fall when microbial activity was still high and plant demand was low. In trenched subplots where vegetative uptake was eliminated, NO3- concentrations in soil leachate (60 cm) rose to between 15 and 35 mg N L-1 in the first year and remained high in the second year. Other studies reported higher magnitudes of NO3- leaching from treated plots. These studies and the findings reported here shown the characteristics of the sludge being applied to land are at least as important as the physical and chemical characteristics of the site to which they are to be applied.
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    URL: http://dx.doi.org/10.1023/A:1005086413282
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    Long-Term Transformation and Redistribution of Potentially Toxic Heavy Metals in Arid-Zone Soils: II. Incubation at the Field Capacity Moisture Content (1999)
    Springer
    Water, air & soil pollution 114 (1999), S. 221-250 
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    ISSN: 1573-2932
    Keywords: arid-zone soils ; field capacity ; fractionation ; heavy metals ; kinetics ; redistribution ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Solid-phase transformation of added Cd, Cu, Cr, Ni, Pb and Zn, in two arid-zone soils incubated in the field capacity moisture regime for one year, were studied. The heavy metals were fractionated into six empirically defined fractions using a selective sequential dissolution (SSD) protocol optimized for arid-zone soils. Each of these fractions was named based on the major soil component targeted for dissolution during the specific SSD step, but it is not assumed that they are mineralogically and chemically totally specific. The transformations of the metals in the two soils incubated at the field capacity regime were compared with those at the moisture saturation regime (Han and Banin, 1997). An initial fast stage of transformation of the soluble metals from the exchangeable (EXC) fraction to the less labile fractions (the carbonate (CARB) fraction for Cd, Pb, Zn, Ni and Cu, and the organic matter (OM) fraction for Cr, and to some extent Cu and Ni) occurred during the fractionation and within one hour after addition. This was followed by a second stage, involving long-term transformation processes of all metals: added Cd was transferred from the EXC into the CARB fraction; added Cr was transferred from the CARB to the OM fraction and Pb was transferred very slowly to the easily reducible oxide (ERO) fraction. Added Cu, Ni and Zn were transferred from the EXC and CARB fractions into the ERO fraction and to some extent OM and RO fractions. In Part I of this series, we reported that during incubation in the saturated moisture regime, Zn and Ni were transferred mainly into the RO and OM fractions. Cadmium, Cr and Pb underwent the same transformation pathways during the slow long-term process, with slightly different rates, in both water regimes. At low levels of addition, the incubated soils moved over one year towards a distribution similar to that of the native soil. At higher levels, the soils still remained removed from the quasi-equilibrium which characterized the native soil, even at the end of one year of incubation.
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    URL: http://dx.doi.org/10.1023/A:1005006801650
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    Trends in Nitrogen Transport in Swedish Rivers (1999)
    Springer
    Environmental monitoring and assessment 59 (1999), S. 47-72 
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    ISSN: 1573-2959
    Keywords: flow-normalisation ; long-term trends ; monitoring ; nitrogen ; riverine load ; statistical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Concern about nitrogen loads in marine environments has drawn attention to the existence and possible causes of long-term trends in nitrogen transport in rivers. The present study was based on data from the Swedish environmental monitoring programme for surface water quality; the continuity of these data is internationally unique. A recently developed semiparametric method was employed to study the development of relationships between runoff and river transport of nitrogen since 1971; the observed relationships were then used to produce time series of flow-normalised transports for 66 sites in 39 river basins. Subsequent statistical analyses of flow-normalised data revealed only few significant downward trends (p ≤0.05) during the time period 1971–1994, and the most pronounced of these downward trends were caused by reduced point emissions of nitrogen. The number of significant upward trends was substantially larger (15 for total-N and 18 for NO3-N). Closer examination of obtained results revealed the following: (i) the most pronounced upward trends were present downstream of lakes, and (ii) observed increases in nitrogen transport coincided in time and space with reduced point emissions of phosphorus or organic matter. This indicated that changes in the retention of nitrogen in lakes were responsible for the upward nitrogen trends. The hypothesis that nitrogen saturation of forest soils has caused a general increase in the riverine export of nitrogen from forested catchments in Sweden was not confirmed. Neither did the results indicate that improved agricultural practices have reduced the export of nitrogen from agricultural catchments.
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    Electrochemical Treatment of Nitrite Using Stainless Steel Electrodes (1999)
    Springer
    Water, air & soil pollution 109 (1999), S. 429-442 
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    ISSN: 1573-2932
    Keywords: electrochemical treatment ; kinetics ; nitrite ; stainless steel electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The efficiency of nitrite removal in an electrochemical cell was investigated in this study using stainless steel electrodes. The experiments were designed to study the effects of current input, volume of the solution, initial pH, and number of electrodes on removal of nitrite at a concentration typical to aquaculture system effluents. Current variation causes opposite trends, while an increase in current would increase the oxidizing efficiency of the system, the voltage induced increase in pH due to hydrogen evolution would decrease the efficiency of the oxidizing agent formed. However, the highest nitrite removal was achieved at a current of 2 A and a complete removal was attained after a duration of ten minutes. A first order reaction model was developed to predict the effect of current on nitrite removal. The energy consumption was directly proportional to the initial pH and the solution volume, while it was inversely proportional to the number of electrodes.
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    Weekly Measurements over One Year of Ammonia Concentrations and Surface Exchange Fluxes at a Danish Heathland with Passive Wind-Vane Flux Samplers in an Aerodynamic Gradient Configuration (1999)
    Springer
    Water, air & soil pollution 113 (1999), S. 357-370 
    Details
    ISSN: 1573-2932
    Keywords: canopy resistance ; deposition ; emission ; micro-meterological approach ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The present study aims to establish the annual NH3 deposition to an inland heathland in Denmark using a micro-meterological approach with passive wind-vane flux samplers. The integrating samplers were replaced at weekly intervals from May 1995 to May 1996. The average concentration, 2.05 μg m-3 at the heathland is at a moderate level when compared to heathlands in other parts of Europe. The average deposition velocity was 0.83 cm s-1 which is within the range of depositon velocities found for other heathlands in Europe. The average canopy resistance was found to be relatively high, 61 s -1. The measurements yielded a total NH3-N deposition of 2.4 (± 0.9) kg ha-1 yr-1 with a data coverage of 71% for 1995/1996. In 40% of this time the flux is regarded as zero because the flux is not significant different from zero. In 60% of this time the significant fluxes varied from –0.052 μg m-2 s-1 (deposition equal 16.4 kg N ha-1 yr-1) to 0.089 μg m-2 s-1 (emission equal 28.2 kg N ha-1 yr-1). The method is only able to direct measure significant fluxes down to the equivalence of 0.010 μg m-2 s-1 (approximately 3.2 kg ha-1 yr-1). Therefore the exact deposition cannot be determined by the applied method at very low deposition sites such as a coastal heathland in Denmark. In a high-deposition area as in the central Netherlands the method gave significant fluxes with a 100% data coverage for a two month period.
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    Estimation and Prediction in the Spatial Linear Model (1999)
    Springer
    Water, air & soil pollution 110 (1999), S. 215-237 
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    ISSN: 1573-2932
    Keywords: acid-precipitation ; best linear unbiased estimation ; best linear unbiased prediction ; environmental monitoring ; geostatistics ; mixed linear models ; trend surface analysis ; universal kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Often in environmental monitoring studies interesting ecological factors will be observed at several locations repeatedly over time. Generally these space-time data are subject to a sequential spatial data analysis. In geostatistics, spatial data describing an environmental phenomenon like the pH value in precipitation at several locations are regarded as a realisation from a stochastic process. Component models are used to interpret the spatial variation of the process. Decomposing the spatial process into single components is based on the theory of linear models. Trend surface analysis is seen to be the geostatistical method for best linear unbiased estimation (BLUE) of the trend component, whereas universal kriging is equivalent to best linear unbiased prediction (BLUP) of the realisation of the spatial process. Furthermore trend surface analysis and universal kriging are shown to agree with the estimation of fixed effects and prediction of fixed and random effects in mixed linear models. Since estimation and prediction for spatial data result in different interpolations the differences are explained also graphically by example. The example uses acid-precipitation monitoring data. The extension of these spatial methods for application to space-time problems by combination with dynamic linear models is treated in the discussion.
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    Effects of Nitrogen and Phosphorus Supply on Hexadecane Biodegradation in Soil Systems (1999)
    Springer
    Water, air & soil pollution 111 (1999), S. 1-18 
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    ISSN: 1573-2932
    Keywords: biodegradation ; hydrocarbon ; nitrogen ; nutrient ratios ; phosphorus ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The biodegradation of hexadecane (C as hexadecane-C) was assessed under 34 different external nitrogen (N supplied as NO3-N) and phosphorus (P supplied as PO4-3-P) supply conditions in order to determine how different nutrient formulations affected nutrient limitation conditions during degradation. CO2 production yields indicated that shifts in N and P supply levels resulted in variable biodegradation responses due to shifts in the limiting-nutrient (e.g., from N to P). For example, the estimated maximum fractional CO2 yield ratio was 0.24 (mg CO2-C produced mg-1 hexadecane-C) for P-limited nutrient formulations (P:hexadecane-C〈0.01), whereas the yield ratio was more than two times greater when the system was not P- limited. Similar effects were observed for N-limited (N:hexadecane- C〈0.15) versus non-N-limited formulations. The relative bioavailability of natural soil-N and soil-P also was examined. In the soil studied, background soil-N was 96.3% organic-N and was found to be largely nonbioavailable. In contrast, high CO2 yields were observed even when no external P was supplied. An iterative mathematical procedure indicated that the Olsen soil-P subfraction (inorganic soil-P plus soluble organic soil- P) best approximated bioavailable soil-P for this soil. Our results indicate that both N and P additions affect biodegradation yields, but that stoichiometrically inappropriate nutrient mixes produce suboptimal CO2 yields. We also found that the bioavailable fractions of soil-N and soil-P should be incorporated into estimating the most suitable nutrient formulations for a given contamination scenario.
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    Relationship Between Landscape Characteristics, History, and Lakewater Acidification in the Adirondack Mountains, New York (1999)
    Springer
    Water, air & soil pollution 112 (1999), S. 407-427 
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    ISSN: 1573-2932
    Keywords: acidic deposition ; Adirondack mountains ; disturbance ; modeling ; nitrogen ; sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Interactions between acidic deposition and watershed characteristics were evaluated for a group of lakes in the Adirondack Mountains, New York. Landscape characteristics were compiled and examined relative to paleolimnological inferences of historical acidification. Results of estimates of acidification using the Model of Acidification of Groundwater in Catchments (MAGIC) and paleolimnological analysis were compared to physical, biological, and landscape change data, including such factors as watershed disturbance, logging, fire, and windthrow, to evaluate if inclusion of additional processes could improve model estimates. Results of bivariate and multivariate analysis confirmed that lakes that have experienced historical acidification tend to be those that receive relatively high amounts of precipitation and have short hydraulic residence times. These variables explained 58% of the diatom-inferred acidification. A combined model of long-term precipitation amount, hydraulic residence time, and recent blowdown accounted for 71% of the historic acidification in the Adirondacks. Lakes that have increased in pH since pre-industrial times tend to be those subject to substantial human disturbance and those that burned during major fires recorded after 1900. The magnitude of the discrepancy between MAGIC model and diatom-inferred hindcasts of acidification was not significantly correlated with any of the landscape change variables, suggesting that additional modifications to the MAGIC model to take into account landscape change are not likely to appreciably improve model performance.
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    Some Effects of N on Ectomycorrhizal Diversity of Scots Pine (Pinus Sylvestris L.) in Northeastern Germany (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 135-140 
    Details
    ISSN: 1573-2932
    Keywords: mycorrhiza ; Pinus sylvestris ; nitrogen ; diversity ; mycorrhizal frequency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In the last three decades high industrial nitrogen (N) emissions have led to eutrophication of a Scots pine stand (Pinus sylvestris [L.]) near Schwedt characterized by a broad cover of Calamagrostis epigejos [L.] Roth (Poaceae). In comparison to the relatively unimpacted control site (low N site), this high N site showed a remarkably low mycorrhizal frequency (percentage of mycorrhizas on total amount of root tips) with seasonal lows down to 27 %. At the low N site the highest number of mycorrhizal root tips was found in the organic layer. At the high N site the amount of mycorrhizas per soil volume was similar in both organic and mineral soil layers, and also significantly lower when compared to the amount at the low N site. The high N site revealed only nine mycorrhizal morphotypes instead of eighteen found at each sampling date at the control site. 80 % of the coenosis at the high N site were represented by only four morphotypes resulting in a low diversity. The seasonal decrease in the mycorrhizal frequency, the small amount of mycorrhizas and the low diversity suggest that the high N deposition at this site has reduced the ability of the pine trees to withstand natural stresses such as prolonged drought or frost periods. This corresponds well with the 42 % reduction in tree stocking density at the high N site compared to the low N site.
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    Use of the Urease Inhibitor N-(n-BUTYL)-Thiophosphoric Triamide Decreased Nitrogen Leaching from Urea in a Fine Sandy Soil (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 587-595 
    Details
    ISSN: 1573-2932
    Keywords: groundwater ; nitrogen ; sandy soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Application of soluble forms of nitrogen (N) fertilizers to citrus trees in sandy soils of central Florida may cause leaching of NO 3 − below the rooting depth. A leaching column study was conducted to evaluate the leaching of urea, NH 4 + and NO3 − forms of N from calcium nitrate, urea, and urease inhibitor coated urea (Agrotain: N-(-n butyl) thiophosphoric triamide (NBPT)) applied to a Candler fine sand (hyperthermic, uncoated Typic Quartzipsamments) during six cycles of intermittent leaching with 220 mL each of water (total 1320 mL) through the soil columns (equivalent to 30 cm rainfall). The amount of NO3-N recovered in the leachate from calcium nitrate treated soil accounted for 43% of the total N applied. Leaching of N from urea and Agrotain treated soil was pronounced during the second and third leaching events. Cumulative leaching of urea form of N accounted for 12 and 8% of total N applied as urea and Agrotain, respectively. The cumulative amounts of NO3-N and NH4-N recovered in six leachate fractions from urea treated soil accounted for 14 and 21%, respectively, of the total N applied to the column. The corresponding values for the Agrotain treated soil were 8 and 17%, respectively. Soil analysis after the completion of leaching showed no urea throughout the entire depth of column in either urea or Agrotain treatments. The total recovery of N (leachate plus soil) was 48.1, 40.4, and 49.7% of total N applied as urea, Agrotain, and calcium nitrate, respectively. This study demonstrated a significant reduction in leaching of N forms from Agrotain as compared with that from urea.
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    Atmospheric Deposition of Acidifying and Eutrophicating Substances in Dune Slacks (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 461-477 
    Details
    ISSN: 1573-2932
    Keywords: calcium ; exchangeable base cations ; nitrogen ; potential acid ; Schoenus nigricans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The atmospheric input of nitrogen and potantial acid, and the composition of the leachate from the topsoil layer are quantified for eight dune slack sites differing in plant composition, on the Frisian islands of Terschelling and Schiermonnikoog. Basiphilous mesotrophic communities with many rare plant species grow in one site on Terschelling and two sites on Schiermonnikoog. Samples were taken in the period mid May 1992 – mid May 1993. Bulk atmospheric nitrogen deposition measured in an open collector was between 15–20 kg ha−1 yr−1 for the eight sites. On Terschelling, the deposition was slightly higher than on Schiermonnikoog. Ammonium was a third of the total amount of nitrogen deposited on Terschelling and half the amount of nitrogen deposited on Schiermonnikoog. The deposition of potential acid varied from 490 to 810 mol ha−1 yr−1. On Terschelling, the amount of potential acid was highest and around 800 mol ha−1 yr−1 for both sites. On Schiermonnikoog, the amount of potential acid was lowest for the dune slacks in the north-western part of the island and it showed an increase for slacks towards the eastern part of the island. Calcium is the main cation leached from the topsoil followed by sodium, magnesium and potassium. Nitrogen or ammonium hardly leached from the topsoil layer. The shift from basiphilous pioneer communities toward older and more acid stages of dune slack succession appears to be caused primarily by leaching of base cations rather than eutrophication.
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    Molecular structure of trans-[Co(NH3)4(NH2CH3)Cl](ClO4)2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 69-72 
    Details
    ISSN: 1572-8854
    Keywords: Co(III) complex ; crystal structure ; kinetics ; steric effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the orthorhombic space group Pnma, with a = 7.9209(5), b = 9.818(1), c = 16.867(2) Å, and Z = 4. The structure was solved employing 1864 independent x-ray reflections with I〉2σ(I) by Patterson and difference Fourier techniques and refined by full-matrix least-squares to R = 0.036. The trans-[CO(NH3)4(NH2CH3)Cl](ClO4)2 molecule is on a crystallographic mirror plane. The cobalt ion is in an elongated octahedral coordination with four equatorial ammonia ligands [average Co–N distance equal to 1.966(2) Å], an axial methylamine [Co–N=1.965(3)Å], and an axial chlorine ion [Co–Cl=2.2771(9)Å]. Kinetic steric effects of the complex are interpreted in terms of structural results.
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    Nitrogen uptake and growth of two citrus rootstock seedlings in a sandy soil receiving different controlled-release fertilizer sources (1998)
    Springer
    Biology and fertility of soils 26 (1998), S. 169-172 
    Details
    ISSN: 1432-0789
    Keywords: Key words Urea ; Coated fertilizers ; Ammonium ; nitrogen ; Nitrate nitrogen ; Nitrogen uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Understanding the fate of different forms of nitrogen (N) fertilizers applied to soils is an important step in enhancing N use efficiency and minimizing N losses. The growth and N uptake of two citrus rootstocks, Swingle citrumelo (SC), and Cleopatra mandarin (CM), seedlings were evaluated in a pot experiment using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments) without N application or with 400 mg N kg–1 applied as urea or controlled-release fertilizers (CRF; either as Meister, Osmocote, or Poly-S). Meister and Osmocote are polyolefin resin-coated urea with longevity of N release for 270 days (at 25°C). Poly-S is a polymer and sulfur-coated urea with release duration considerably shorter than that of either Meister or Osmocote. The concentrations of 2 M KCl extractable nitrate nitrogen (NO3 –-N) and ammonium nitrogen (NH4 +-N) in the soil sampled 180 days and 300 days after planting were greater in the soil with SC than with CM rootstock seedlings. In most cases, the extractable NH4 + and NO3 – concentrations were greater for the Osmocote treatment compared to the other N sources. For the SC rootstock seedlings, dry weight was greater with Meister or Poly-S compared with either Osmocote or urea. At the end of the experiment, ranking of the various N sources, with respect to total N uptake by the seedlings, was: Meister = Osmocote 〉 Poly-S 〉 Urea 〉 no N for CM rootstock, and Meister = Poly-S = Osmocote 〉 Urea 〉 no N for SC rootstock. The study demonstrated that for a given rate of N application the total N uptake by seedlings was greater for the CRF compared to urea treatment. This suggests that various N losses were lower from the CRF source as compared to those from soluble fertilizers.
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    URL: http://dx.doi.org/10.1007/s003740050363
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    Geological Controls of Variograms in a Complex Carbonate Reservoir, Eastern Province, Saudi Arabia (1998)
    Springer
    Mathematical geology 30 (1998), S. 309-322 
    Details
    ISSN: 1573-8868
    Keywords: variograms ; geostatistics ; geological controls ; reservoir characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract To derive meaningful results from a geostatistical study, it is extremely important to establish the relationship between geology and variograms. However, it is not always easy to establish such a relationship, mainly because of the inadequacy of quantitative or qualitative information. Large amounts of reliable well-log porosity data and the detailed geological information from a complex carbonate reservoir located in the Eastern Province of Saudi Arabia provided an ideal case study of the relationships between geology and variograms. The reservoir under consideration is in the form of a gently dipping, elongated anticline and consists of three productive zones which have been subdivided into several lithologically distinct layers. Results, which indicate an excellent match between geology and porosity variograms, are summarized as follows: (1) use of stratigraphic distances resulted in considerable improvement in the behavior of variograms, (2) structurally controlled geometrical anisotropy is the most obvious feature of variograms, and (3) layers consisting of more complex lithologic framework provided variograms with relatively greater nugget variances and shorter ranges. These results provide further insight into geology and form a meaningful basis for estimation and simulation of the reservoir. They also could be used as a general guide in the geostatistical study of similar carbonate reservoirs.
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    An Improved Perturbation Mechanism for Simulated Annealing Simulation (1998)
    Springer
    Mathematical geology 30 (1998), S. 801-816 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; stochastic simulation ; Monte Carlo simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Simulated annealing (SA) is being increasingly used for the generation of stochastic models of spatial phenomena because of its flexibility to integrate data of diverse types and scales. The major shortcoming of SA is the extensive CPU requirements. We present a perturbation mechanism that significantly improves the CPU speed. Two conventional perturbation mechanisms are to (1) randomly select two locations and swap their attribute values, or (2) visit a randomly selected location and draw a new value from the global histogram. The proposed perturbation mechanism is a modification of option 2: each candidate value is drawn from a local conditional distribution built with a template of kriging weights rather than from the global distribution. This results in accepting more perturbations and in perturbations that improve the variogram reproduction for short scale lags. We document the new method, the increased convergence speed, and the improved variogram reproduction. Implementation details of the method such as the size of the local neighborhood are considered.
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    Maximum Likelihood Estimation of Spatial Covariance Parameters (1998)
    Springer
    Mathematical geology 30 (1998), S. 95-108 
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    ISSN: 1573-8868
    Keywords: geostatistics ; maximum likelihood estimation ; spatial covariance ; sampling distribution ; mean square error
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract In this paper, the maximum likelihood method for inferring the parameters of spatial covariances is examined. The advantages of the maximum likelihood estimation are discussed and it is shown that this method, derived assuming a multivariate Gaussian distribution for the data, gives a sound criterion of fitting covariance models irrespective of the multivariate distribution of the data. However, this distribution is impossible to verify in practice when only one realization of the random function is available. Then, the maximum entropy method is the only sound criterion of assigning probabilities in absence of information. Because the multivariate Gaussian distribution has the maximum entropy property for a fixed vector of means and covariance matrix, the multinormal distribution is the most logical choice as a default distribution for the experimental data. Nevertheless, it should be clear that the assumption of a multivariate Gaussian distribution is maintained only for the inference of spatial covariance parameters and not necessarily for other operations such as spatial interpolation, simulation or estimation of spatial distributions. Various results from simulations are presented to support the claim that the simultaneous use of maximum likelihood method and the classical nonparametric method of moments can considerably improve results in the estimation of geostatistical parameters.
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    URL: http://dx.doi.org/10.1023/A:1021765405952
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    An Alternative to Cokriging for Situations with Small Sample Sizes (1998)
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    Mathematical geology 30 (1998), S. 259-274 
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    ISSN: 1573-8868
    Keywords: cokriging ; small sample size ; pedotransfer functions ; geostatistics ; parameter uncertainty ; measurement error
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Lack of large datasets in soil protection studies and environmental engineering applications may deprive these fields of achieving accurate spatial estimates as derived with geostatistical techniques. A new estimation procedure, with the acronym Co_Est, is presented for situations involving primary and secondary datasets of sizes generally considered too small for geostatistical applications. For these situations, we suggest the transformation of the secondary dataset into the primary one using pedotransfer functions. The transformation will generate a larger set of the primary data which subsequently can be used in geostatistical analyses. The Co_Est procedure has provisions for handling measurement errors in the primary data, estimation errors in the converted secondary data, and uncertainty in the geostatistical parameters. Two different examples were used to demonstrate the applicability of Co_Est. The first example involves estimation of hydraulic conductivity random fields using 42 measured data and 258 values estimated from borehole profile descriptions. The second example consists of estimating chromium concentrations from 50 measured chromium data and 150 values estimated from a relationship between chromium and copper concentrations. The examples indicate that in situations where the size of the primary data is small, Co_Est can produce estimates which are comparable to cokriging estimates.
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    URL: http://dx.doi.org/10.1023/A:1021724830427
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    Nitrogen fixation and the mass balances of carbon and nitrogen in ecosystems (1998)
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    Biogeochemistry 43 (1998), S. 63-78 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; mass balance ; nitrogen ; nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Ecosystems with high rates of nitrogen fixation often have high loss rates through leaching or possibly denitrification. However, there is no formal theoretical context to examine why this should be the case nor of how nitrogen accumulates in such open systems. Here, we propose a simple model coupling nitrogen inputs and losses to carbon inputs and losses. The nitrogen balance of this model system depends on plant (nitrogen fixer) growth rate, its carrying capacity, N fixed/C fixed, residence time of nitrogen and carbon in biomass, litter decay rate, litter N/C, and fractional loss rate of mineralized nitrogen. The model predicts the requirements for equilibrium in a nitrogen-fixing system, and the conditions on nitrogen fixation and losses in order for the system to accumulate nitrogen and carbon. In particular, the accumulation of nitrogen and carbon in a nitrogen-fixing system depend on an interaction between residence time in vegetation and litter decay rate in soil. To reflect a possible increased uptake of soil nitrogen and decreased respiratory cost of symbiotic nitrogen fixers, the model was then modified so that fixation rate decreased and growth rate increased as nitrogen capital accumulated. These modifications had only small effects on carbon and nitrogen accumulation. This suggests that switching from uptake of atmospheric nitrogen to mineral soil nitrogen as nitrogen capital accumulates simply results in a trade-off between energetic limitations and soil nitrogen limitations to carbon and nitrogen accumulation. Experimental tests of the model are suggested.
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    URL: http://dx.doi.org/10.1023/A:1006057428096
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    Plant-soil Interactions in Deserts (1998)
    Springer
    Biogeochemistry 42 (1998), S. 169-187 
    Details
    ISSN: 1573-515X
    Keywords: aridisols ; desertification ; erosion ; geostatistics ; Larrea tridentata ; nitrogen ; phosphorus ; Prosopis glandulosa ; soil heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Geostatistical analyses show that the distribution of soil N, P and K is strongly associated with the presence of shrubs in desert habitats. Shrubs concentrate the biogeochemical cycle of these elements in ‘islands of fertility’ that are localized beneath their canopies, while adjacent barren, intershrub spaces are comparatively devoid of biotic activity. Both physical and biological processes are involved in the formation of shrub islands. Losses of semiarid grassland in favor of invading shrubs initiate these changes in the distribution of soil nutrients, which may promote the further invasion and persistence of shrubs and cause potential feedbacks between desertification and the Earth's climate system.
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    URL: http://dx.doi.org/10.1023/A:1005939924434
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    Depth of the base of the Jackson aquifer, based on geophysical exploration, southern Jackson Hole, Wyoming, USA (1998)
    Springer
    Hydrogeology journal 6 (1998), S. 374-382 
    Details
    ISSN: 1435-0157
    Keywords: Key words geophysical methods ; groundwater exploration ; geostatistics ; unconsolidated sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Une campagne géophysique a été entreprise pour préciser la profondeur du mur de l'aquifère dans le secteur sud de Jackson Hole (Wyoming, États-Unis). Des mesures audio-magnétotelluriques (audio MT) sur 77 sites de ce secteur ont fourni des logs de résistivitéélectrique du sous-sol ; les variations de la lithologie en fonction de la profondeur en ont été déduites. Un niveau géoélectrique à 100–600 ohm.m, dénommé "aquifère de Jackson", a servi à définir des dépôts superficiels quaternaires saturés en eau et non consolidés. La profondeur médiane de la base de l'aquifère de Jackson est de l'ordre de 61 m, à partir des 62 sites ayant fourni suffisamment de données de résistivité. Les valeurs audio MT mesurées ont été krigées afin d'estimer la profondeur de la base de la formation aquifère dans la partie sud de Jackson Hole. Les cartes d'isovaleurs d'estimation krigées indiquent que la profondeur de la base de la formation aquifère de Jackson est faible dans la partie centrale de la zone d'étude à l'est et à l'ouest des monts Gros Ventre, plus grande dans le secteur ouest près de la zone faillée de Teton, et faible sur la bordure sud de Jackson Hole. Les profondeurs estimées vont de 30 m au sud, près des confluences des rivières Spring et Flat avec la rivière Snake, à 210 m à l'ouest près de la ville de Wilson (Wyoming).
    Abstract: Resumen Se llevó a cabo una campaña geofísica para determinar la profundidad del basamento de un acuífero libre en la zona sur de Jackson Hole, Wyoming, EEUU. USA. Medidas audio-magnetotelúricas (ATM) en 77 lugares de la zona de estudio dieron lugar a registros de resistividad eléctrica del subsuelo, que se usaron para inferir los cambios litológicos con la profundidad. Los depósitos superficiales, saturados y no consolidados de edad cuaternaria, el acuífero de Jackson, forman una capa de resistencia geoeléctrica entre 100–600 ohm-m. La profundidad media de la base del acuífero de Jackson se estima en unos 61 m (200 pies), a partir de 62 registros con medidas suficientes. Los valores ATM fueron krigeados para obtener una medida de la profundidad del basamento del acuífero en la zona sur de Jackson Hole. Los mapas de isoprofundidades obtenidos por krigeado indican que el acuífero es poco profundo en la parte central de la zona de estudio, cerca de los Gros Ventre Buttes orientales y occidentales, más profundo al oeste, cerca del sistema de fallas de Teton, y menos profundo en el borde sur de Jackson Hole. Las profundidades van desde 30 m (100 pies) en el sur, en la confluencia entre los desfiladeros Spring y Flat con el Río Snake, hasta 210 m (700 pies) al oeste, cerca de la ciudad de Wilson, Wyoming.
    Notes: Abstract  A geophysical survey was conducted to determine the depth of the base of the water-table aquifer in the southern part of Jackson Hole, Wyoming, USA. Audio-magnetotellurics (AMT) measurements at 77 sites in the study area yielded electrical-resistivity logs of the subsurface, and these were used to infer lithologic changes with depth. A 100–600 ohm-m geoelectric layer, designated the Jackson aquifer, was used to represent surficial saturated, unconsolidated deposits of Quaternary age. The median depth of the base of the Jackson aquifer is estimated to be 200 ft (61 m), based on 62 sites that had sufficient resistivity data. AMT-measured values were kriged to predict the depth to the base of the aquifer throughout the southern part of Jackson Hole. Contour maps of the kriging predictions indicate that the depth of the base of the Jackson aquifer is shallow in the central part of the study area near the East and West Gros Ventre Buttes, deeper in the west near the Teton fault system, and shallow at the southern edge of Jackson Hole. Predicted, contoured depths range from 100 ft (30 m) in the south, near the confluences of Spring Creek and Flat Creek with the Snake River, to 700 ft (210 m) in the west, near the town of Wilson, Wyoming.
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    Peroxy Radical Kinetics Resulting from the OH-Initiated Oxidation of 1,3-Butadiene, 2,3-Dimethyl-1,3-Butadiene and Isoprene (1998)
    Springer
    Journal of atmospheric chemistry 29 (1998), S. 267-298 
    Details
    ISSN: 1573-0662
    Keywords: peroxy radicals ; kinetics ; conjugateddienes ; biogenic VOC ; degradation mechanisms ; tropospheric ozone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The laser flash photolysis/UV absorption spectrometry technique has been used to investigate the kinetics of the peroxy radical permutation reactions (i.e. self and cross reactions) arising from the OH-initiated oxidation of isoprene (2-methyl-1,3-butadiene), and of the simpler, but related conjugated dienes, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene. The results of the two simpler systems are analysed to provide values of the rate coefficients for the 6 peroxy radical permutation reactions of the three types of isomeric peroxy radical produced in each system (T = 298 K, P = 760 Torr). The rate coefficients are all significantly larger than values estimated previously by extrapolation of structure-reactivity relationships based on the kinetics of a limited dataset of simpler radicals containing similar structural features. The results are discussed in terms of trends in self and cross reaction reactivity of primary, secondary and tertiary peroxy radicals containing combinations of allyl, β-hydroxy and δ-hydroxy functionalities. Since the peroxy radicals formed in these systems are structurally very similar to those formed in the isoprene system, the kinetic parameters derived from the results of the simpler systems are used to assist the assignment of kinetic parameters to the 21 permutation reactions of the six types of isomeric peroxy radical generated in the isoprene system. Kinetic models describing the OH-initiated degradation of all three conjugated dienes to first generation products in the absence of NOx are recommended, which are also consistent with available end product studies. The model for isoprene is considered to be a further improvement on that suggested previously for its OH-initiated oxidation in the absence of NOx. The mechanism is further extended to include chemistry applicable to ‘NOx-present’ conditions, and calculated product yields are compared with those reported in the literature.
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    Kinetics of the Gas-Phase Reactions of OH and NO3 Radicals and O3 with the Monoterpene Reaction Products Pinonaldehyde, Caronaldehyde, and Sabinaketone (1998)
    Springer
    Journal of atmospheric chemistry 31 (1998), S. 281-297 
    Details
    ISSN: 1573-0662
    Keywords: hydroxyl radical ; nitrate radical ; ozone ; pinonaldehyde ; caronaldehyde ; sabinaketone ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Using a relative rate method, rate constants have been measured for the gas-phase reactions of OH and NO3 radicals with pinonaldehyde, caronaldehyde and sabinaketone at 296 ± 2 K. The OH radical reaction rate constants obtained are (in units of 10−12 cm3 molecule−1 s−1): pinonaldehyde, 48 ± 8; caronaldehyde, 48 ± 8; and sabinaketone, 5.1 ± 1.4, and the NO3 radical reaction rate constants are (in units of 10−14 cm3 molecule−1 s−1): pinonaldehyde, 2.0 ± 0.9; caronaldehyde, 2.5 ± 1.1; and sabinaketone, 0.036 ± 0.023, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. Upper limits to the O3 reaction rate constants were also obtained, of 〈2 × 10−20 cm3 molecule−1 s−1 for pinonaldehyde and caronaldehyde, and 〈5 × 10−20 cm3 molecule−1 s−1 for sabinaketone. These reaction rate constants are combined with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals and O3 to calculate tropospheric lifetimes and dominant transformation process(es) of these and other monoterpene reaction products.
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    Holling's Figure-Eight Model: A Technical Reevaluation in Relation to Climate Change and Biodiversity (1998)
    Springer
    Environmental monitoring and assessment 49 (1998), S. 157-168 
    Details
    ISSN: 1573-2959
    Keywords: biodiversity ; carbon storage ; climate change ; conservation ; creative destruction ; ecological succession ; ecosystem stability ; Holling figure-eight ; nitrogen ; resilience
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Holling proposed a four-phase conceptual model of ecosystem dynamics that includes exploitation, conservation, and destructive and renewal components to explain the failure of many natural resource management schemes. The model is drawn as a sideways figure-eight i.e. ∞. There are two dimensions in this model, connectivity (abscissa) and the amount of capital stored in the system (ordinate). This conceptual model has been suggested as a guide to thinking about the impact of climate change on biodiversity, but the two dimensions are insufficient and the alignment of the figure-eight model is problematic when compared with actual data. Kay has adjusted the dimensions of the figure-eight model and renamed the abscissa as exergy stored and the ordinate as exergy consumed. We realign the original figure-eight model, labeling the abscissa as carbon stored and the ordinate as nutrients, such that the relative values of both axes are in qualitative agreement with data from four different studies. This new alignment is then shown to fit relatively well with Holling's original labels. This revision of the figure-eight model brings Holling's model into agreement with observations and provides insight into the linkages between biodiversity and climate change.
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    Spatial and Temporal Variabilities in Nitrogen and Phosphorous in the Nakdong River System, Korea (1998)
    Springer
    Water, air & soil pollution 102 (1998), S. 37-60 
    Details
    ISSN: 1573-2932
    Keywords: behavior ; distribution ; Nakdong River ; nitrogen ; phosphorus ; spatial ; temporal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The concentrations of nitrogen (N) and phosphorous (P) species and relevant hydrographic parameters were determined in main stream and tributary waters of the Nakdong River system during the periods of May through October 1994. During the entire period, the total N (TN) and total P (TP) concentrations in surface waters were found within the ranges of 0.4–7.0 (N=241) and 0.02–1.536 mg L-1 (N=241), respectively. To help derive meaningful interpretations of temporal and geographical variabilities in the nutrient bahavior, the entire data were evaluated for each individual parameter after employing several different grouping schemes. The results of this comparative analysis can be expressed in terms of: (1) high summer/fall ratios for most of nutrient species; and (2) low summer/fall ratios for most of nutrient-to-nutrient ratios and relevant hydrographic parameters. Interestingly, while the former case was found to be more significant in tributary waters than main stream waters, such geographical dependence was not strongly evident for the latter case. A z-statistic test, conducted to check the significance of temporal (between summer and fall) and spatial (between tributary and main stream regions) differences, confirm that the observed variabilities are in most cases strong enough for most of variables studied – nutrient species, their ratios, and relevant hydrographic parameters. In addition, comparison of nutrient species between dissolved and particulate phases reveals several interesting features. Unlike dissolved nutrient species, the concentrations of particulate N or P (PN or PP) exhibited quite extraoridanry behavior. While PN appears to be rather minor component of the total N budget for the Nakdong river, PP seems to make rather strong contributions to its total P budgets with its strong input from tributary waters during rainy summer season. Through an application of correlation analysis, relationships between different parameters were investigated for both before and after the grouping of data sets. The overall picture of this analysis showed that nutrient species were strongly correlated with each other, while the strongest correlations were among such hydrographic parameters as DO, BOD, COD, and conductivity. This analysis was further conducted to more deliberately divided data groups. The results of analyses on these sub-grouped data sets indicate that the occurrences of significant corelations were common from tributary waters relative to main streams for both (1) between different nutrient species and (2) between nutrient and hydrographic parameters. Using the line of evidence gathered from the statistical tests and from the correlation analysis, we conclude that the environmental health of the Nakdong river system is affected by the combined effects of various factors and processes.
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    URL: http://dx.doi.org/10.1023/A:1004973616860
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    Leaching of Nutrients, Organic Carbon and Iron from Finnish Forestry Land (1998)
    Springer
    Water, air & soil pollution 105 (1998), S. 239-250 
    Details
    ISSN: 1573-2932
    Keywords: Finland ; forested catchments ; iron ; leaching ; nitrogen ; nutrients ; organic carbon ; peatland ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This study provides an assessment of the spatial variability of the long-term leaching of nutrients, total organic carbon (TOC) and iron (Fetot) from 22 forested catchments (0.69-56 km2), distributed across all but the northenmost areas of Finland. The natural, unmanaged Kruunuoja catchment is located in a national park, while the other catchments represent Finnish forestry land. The average leaching of Ptot (4.2 kg km-2 yr-1) from the Kruunuoja catchment was small compared to the catchments representing forestry land (on average 10 kg km-2 yr-1). Moreover, P fertilization was the most important predictor for the spatial variation in Ptot leaching (r2=0.45). Leaching of TOC, Fetot and N compounds was not closely related to forestry practices. Median C/N ratio in the study streams was high (range 34-66). The average inorganic N proportion and leaching of Ptot were lowest in the Kruunuoja catchment (7.3 % and 2.8 kg km-2 yr-1, respectively) and highest in the southernmost Teeressuonoja catchment (54 % and 100 kg km-2 yr-1, respectively) located in the highest N deposition area. The most important forestry practices since the 1960's have affected about 2.4 % of the area of study sites per year (cf. 2% in the entire country in 1991). Moreover, the mean annual runoff from the catchments (230-430 mm yr-1) agrees with the mean annual runoff from Finland (301 mm yr-1). Consequently, the results of the study catchments can be used to estimate average total annual leaching from Finnish forestry land: 2,700 t of Ptot, 48,000 t of Ntot, 110,000 t of Fetot and 1.5 million t of TOC.
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    Estimation of Nutrient Atmospheric Deposition to Long Island Sound (1998)
    Springer
    Water, air & soil pollution 105 (1998), S. 521-538 
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    ISSN: 1573-2932
    Keywords: atmosperic deposition ; Long Island Sound ; modeling ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Anthropogenic nutrient sources (especially nitrogen and phosphorus) released into the Long Island Sound (LIS) causes excessive phytoplankton growth resulting in hypoxic conditions. Atmospheric deposition (both wet and dry deposition) has significant effect on aquatic and terrestrial ecosystems. Two dry deposition monitoring sites were established along the north shore of LIS in February 1991. Wet and dry deposition samples were collected since then. A dry deposition velocity model, based on the characteristics of the water surface, was used to estimate the loading as well as the seasonal variability (dynamics) of nutrients in atmospheric deposition to LIS. The average nitrogen flux from each site was 6.64 kg (as-N) ha-yr-1. The total atmospheric nitrogen loading was estimated to be 2240 metric tons yr-1 which correcponds to 2.5% of the estimated total nitrogen loading to the Sound from all sources. The average phosphorus flux was 37.44 g (as-P) ha-yr-1. The total atmospheric phosphorus loading to the Sound was estimated to be 12.62 metric tons yr-1. The results show that wet deposition was the predominant source of atmospheric contribution to the Sound.
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    Soil and Minespoil Fill as Media for Renovation of Nitrogen and Phosphorus in Domestic Wastewater (1998)
    Springer
    Water, air & soil pollution 102 (1998), S. 361-375 
    Details
    ISSN: 1573-2932
    Keywords: alternative on-site wastewatertreatment and disposal systems ; fill material ; low pressuredistribution systems ; minespoil ; nitrogen ; phosphorus ; wastewater renovation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Development of Appalachian coal mining regions of the USA has been severely hampered by lack of domestic waste disposal technologies suited to fills. The suitability of on-site wastewater treatment and disposal systems (OSWTDS) in fill material is uncertain due to the effects of surface mining on soil physical properties. This research was conducted to evaluate the potential for renovation of N and P present in domestic wastewater by fills produced from mining operations. Nitrogen and P were chosen because of their potential adverse environmental impacts. Soil-fill (a mixture of Jefferson, fine-loamy, siliceous, mesic Typic Hapludult and Muskingom, fine-loamy, mixed, mesic Typic Dystrochrept soils) and minespoil (spoil)-fill (blasted rock material associated with the Taggart Marker and Low Splint Bench coal seams of the Upper Middle Wise Formation) were used in this study. Septic tank effluent (STE) and sand filter effluent (SFE) were applied to spoil-fill columns at four loading rates (0, 5.4, 10.8, and 21.6 L m-2d-1) and spoil-fill columns at one loading rate (21.6 L m-2d-1) for a period of 20 wk. Renovation of wastewater was assessed by determining the concentration of N and P present in column leachate. Reduction of inorganic N (NO3 - + NH4 +), based on N/Cl ratios, ranged from 14.9 to 32.1% after the varying application rates of STE and SFE passed through the soil columns. However, leachate NO3 --N concentrations were still above the 10 mg-1 drinking water standard. The quantity of P emerging from the spoil-fill columns (3.0 mg P L-1) was higher than anticipated and may be related to the indigenous P present in the minespoil. Sorption of P in the soil-fill column decreased with increased STE and SFE application (reductions ranged from 99.1 to 74.4%). Results from this study indicate that there is potential for renovating wastewater in OSWTDS in selected soil-fill areas in reclaimed minelands.
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    Magic, Safe and Smart Model Applications at Integrated Monitoring Sites: Effects of Emission Reduction Scenarios (1998)
    Springer
    Water, air & soil pollution 105 (1998), S. 21-30 
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    ISSN: 1573-2932
    Keywords: acidification ; emission ; MAGIC ; model ; nitrogen ; SAFE ; SMART ; sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Three well-known dynamic acidification models (MAGIC, SAFE, SMART) were applied to data sets from five Integrated Monitoring sites in Europe. The calibrated models were used in a policy-oriented framework to predict the long-term soil acidification of these background forest sites, given different scenarios of future deposition of S and N. Emphasis was put on deriving realistic site-specific scenarios for the model applications. The deposition was calculated with EMEP transfer matrices and official emissions for the target years 2000, 2005 and 2010. The alternatives for S deposition were current reduction plans and maximum feasible reductions. For N, the NOx and NHy depositions were frozen at the present level. For NOx, a reduction scenario of flat 30% reduction from present deposition also was utilized to demonstrate the possible effects of such a measure. The three models yielded generally consistent results. The ‘Best prediction’-scenario (including the effects of the second UN/ECE protocol for reductions of SO2 emissions and present level for NOx-emissions), resulted in many cases in a stabilization of soil acidification, although significant improvements were not always shown. With the exception of one site, the ‘Maximum Feasible Reductions’ scenario always resulted in significant improvements. Dynamic models are needed as a complement to steady-state techniques for estimating critical loads and assessing emission reduction policies, where adequate data are available.
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    URL: http://dx.doi.org/10.1023/A:1005099930089
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    Nitrogen Deposition and Strategies for the Control of Acidification and Eutrophication across Great Britain (1998)
    Springer
    Water, air & soil pollution 107 (1998), S. 121-145 
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    ISSN: 1573-2932
    Keywords: critical loads function ; emissions reductions ; modelling ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract It is now recognised that a multi-pollutant, multi-effect approach needsto be adopted to address the range of problems caused by atmosphericpollution. In this paper we use a relatively simple trajectory model (HARM)to explore the coupled behaviour of sulphur dioxide (SO2),oxides of nitrogen (NOx) and ammonia (NH3) andthe possible effects of future reductions in emissions of these pollutantson depositions of S and N across Great Britain. The performance of HARM withrespect to concentrations and depositions of NOy andNHx is assessed by comparison with data from nationalmonitoring networks. A range of emissions scenarios are modelled and theeffects of these reductions on critical loads exceedance are explored usingthe critical loads function (CLF), which allows both the acidification andeutrophication effects of S and N deposition to be explored simultaneously.Spatial variations in the reductions of deposition of S and/or N required tomeet critical loads are described. Reductions in emissions of the precursorsof strong acids (SO2 and NOx) yield benefits interms of ammonium deposition as a result of their coupled chemistry. Thedevelopment of strategies to control nitrogen deposition will need to take this non-linearity in to account.
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    URL: http://dx.doi.org/10.1023/A:1019832913817
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    Nitrification and Denitrification Estimates in a Louisiana Swamp Forest Soil as Assessed by 15N Isotope Dilution and Direct Gaseous Measurements (1998)
    Springer
    Water, air & soil pollution 106 (1998), S. 149-161 
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    ISSN: 1573-2932
    Keywords: denitrification ; nitrification ; nitrogen ; nitrous oxide ; wetlands ; 15 isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The transformations of applied (100 kg N ha-1)15 N labelled NO3 and NH4 in Mississippi River deltaic plain swamp forest soil which receives agriculture run-off from adjacent sugarcane fields were determined. Using an isotopic dilution technique, the rates of NO3 production (nitrification) and reduction in the 15NO3 treated soil-water-columns were approximately 240 and 2,320 g N ha-1 d-1, whereas NH4 production (mineralization) and removal rates in the 15NH4 treated soil-water-columns were 270 and 2160 g N ha-1 d-1, respectively. It was shown that if nitrification and NH4 assimilation were the primary processes responsible for NH4 removal, average NH4 assimilation would be 145 g N ha-1 d-1. Based on labelled N2-emission, denitrification was 3 fold greater in the NO3 treatment compared to the NH4 treated soil water-columns with rates of 818 and 266 g N ha-1 d-1 respectively. Even though the rate was lower in the NH4 treatment, results show that nitrification-denitrification of NH4 is a significant process. Nitrogen losses determined by15 N2 emissions were 20.4 and 6.4% and N2O emissions were 0.10 and 0.03% of the applied NO3-N and NH4-N, respectively, over 32 days of incubation. Fertilizer loss through N2O emission was only of minor significance compared to the fertilizer loss through N2 evolution. Nitrous oxide fluxes from the control soil-water-columns averaged 9.4 g N ha-1 d-1. Addition of NO3-N to the columns increased N2O production 56% as compared to a 15% increase from the NH4-N addition. Results show that this wetland soil has a large capacity to process inorganic nitrogen entering the system as a result of agriculture run-off.
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    Use of Soft Data in a GIS to Improve Estimation of the Volume of Contaminated Soil (1998)
    Springer
    Water, air & soil pollution 101 (1998), S. 217-234 
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    ISSN: 1573-2932
    Keywords: cyanide ; geostatistics ; GIS ; PAH ; soft data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In the practice of soil remediation, organoleptic observations such as the smell or the colour of contaminated soil play an important role when determining well-defined volumes of contaminated soil. A GIS is then used to combine quantitative measurements with such soft data. In this study general procedures concerning how to deal with this type of observations are presented. The procedures were applied to a former gas works site, which was contaminated with cyanide and polycyclic aromatic hydrocarbons in the Netherlands. The volume of contaminated soil was determined. Use of soft data reduced the uncertainty in the volume of contaminated soil with 4 to 16%.
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    URL: http://dx.doi.org/10.1023/A:1004985516408
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    Modelling the Impact of Lowered Atmospheric Nitrogen Deposition on a Nitrogen Saturated Forest Ecosystem (1998)
    Springer
    Water, air & soil pollution 104 (1998), S. 181-203 
    Details
    ISSN: 1573-2932
    Keywords: coniferous ecosystems ; Douglas fir ; 15N ; NICCCE ; NITREX ; nitrogen ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract For a Douglas fir forest ecosystem subjected to an experimental decrease in nitrogen (N) deposition, N dynamics were simulated using the dynamic simulation model NICCCE. Meteorological driving variables and N concentrations in throughfall were input to the model, that simulated results of a 15N tracer experiment, C and N concentrations in the soil, soil water chemistry and tree biomass. Four years of ambient N deposition, followed by four years of N deposition manipulations by means of a roof construction beneath the forest canopy, were modelled. Simulation of this second period was performed for a high-N treatment (37 kg N ha-1 yr-1) and a low-N treatment with throughfall-N at natural background level (6 kg N ha-1 yr-1). Calibration and model performance is discussed and compared to results of field experiments. The quick response of soil water chemistry after lowering N deposition and the 15N tracer signal observed in soil water at 90 cm soil depth, were simulated closely by the calibrated model. 15NH4-N data could only be simulated by accounting for bypass flow, indicating that throughfall water did not fully interact with the soil. Using the calibrated parameter set of the low-N treatment for the high-N treatment resulted in a lower model performance, although time trends were reproduced well also for this treatment. A sensitivity analysis showed model outcome of N transformations to be very sensitive to soil microbial parameters, such as the C efficiency. Use of the 15N tracer data in the calibration lowered uncertainties of these sensitive model parameters. Evaluation of the N input-output budget and microbial N transformations in the ecosystem revealed that lowering N inputs in this N saturated forest soil resulted in a more than proportional decrease of N leaching losses out of the soil system. Gross N transformations decreased under lowered N input, in particular the formation of NO3-N. Net N mineralization was not affected after four years of N manipulations. Net nitrification was decreased to about one third of the rate observed at the high-N deposition plot. Combining 15N tracer data with dynamic simulation modelling provides a powerful tool to improve model performance and process descriptions, and to evaluate impacts of atmospheric N deposition on N cycling in ecosystems.
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    URL: http://dx.doi.org/10.1023/A:1004992614988
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    Changes in Mass Element Fluxes and their Importance for Critical Loads: Geomon Network, Czech Republic (1998)
    Springer
    Water, air & soil pollution 105 (1998), S. 365-376 
    Details
    ISSN: 1573-2932
    Keywords: catchment ; critical loads ; Czech Republic ; element fluxes ; GEOMON network ; nitrogen ; sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Three years (1994-1996) of runoff, bulk deposition, and throughfall S and N data obtained from GEOMON, a network of 14 small forest catchments in the Czech Republic, are presented. In this paper, we assess regional differences and temporal trends in S and N fluxes under changing regional burdens. Decreases in S deposition have occurred in the emission-burdened northern and western parts of the Czech Republic, where remedial measures have been applied. For example, at the Uhlířská catchment (Jizerské hory Mtns., northern Czech Republic), throughfall S fluxes decreased from 72.7 to 48.5 kg ha-1 yr-1. In contrast, the relatively clean central and southern parts of the Czech Republic showed an increase in S deposition; for example at the Na lizu catchment (Šumava Mtns., southern Czech Republic) throughfall S fluxes increased from 9.0 to 18.8 kg ha-1 yr-1. In burdened catchments with damaged forests, high runoff of N was observed. Using fluxes of S and N measured at the GEOMON sites, we calculated critical loads and exceedances for both S and N in the catchments. The critical loads of S ranged from 505 to 3,631 mol L-1 yr-1 during 1994-1996; in about 80% of the catchments the critical loads were exceeded by atmospheric deposition; half of the catchments showed an exceedance for N.
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    Hydrology and Chemistry of the Choptank River Basin (1998)
    Springer
    Water, air & soil pollution 105 (1998), S. 387-397 
    Details
    ISSN: 1573-2932
    Keywords: Chesapeake Bay ; Choptank River ; iron ; nitrogen ; phosphorus ; river water chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Choptank River basin is a coastal plain catchment dominated by agriculture (52% of land use). We summarize an 11 year data set of discharge and chemistry from a gauged subbasin. Discharge exhibited seasonal variations driven by seasonal evapotranspiration. There were double seasonal maxima of pH, NH4 +, NO3 -, total N, Fe, and total P concentrations in late spring and fall as the saturated zone rose and fell within the soil. Significant interannual variability in discharge was the result of rainfall variation. There were positive nterannual trends in NO3 - concentrations and negative interannual trends in NH4 + and PO4 3- concentrations. These data were combined to estimate N and P export coefficients of 3-11 kg N ha-1 yr-1 and 0.14-0.66 kg P ha-1 yr-1, driven primarily by interannual variations in discharge. These export coefficients are low compared to other coastal plain watersheds dominated by agriculture and may be responsible for the small anthropogenic effects in the Choptank estuary compared to other Chesapeake drainages.
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    Management-induced change in labile soil organic matter under continuous corn in eastern Canadian soils (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 88-94 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass C ; Water-soluble organic carbon ; Light fraction organic carbon ; Fertilizer ; nitrogen ; 13C nuclear magnetic resonance ; Infrared spectrophotometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil samples taken from four experimental sites that had been cropped to continuous corn for 3–11 years in Ontario and Quebec were analyzed to evaluate changes in quantity and quality of labile soil organic carbon under different nitrogen (N) fertility and tillage treatments. Addition of fertilizer N above soil test recommendations tended to decrease amounts of water-soluble organic carbon (WSOC) and microbial biomass carbon (MBC). The quality of the WSOC was characterized by 13C nuclear magnetic resonance and infrared spectrophotometry and the results indicated that carbohydrates, long-chain aliphatics and proteins were the major components of all extracts. Similar types of C were present in all of the soils, but an influence of management was evident. The quantity of soil MBC was positively related to the quantities of WSOC, carbohydrate C, and organic C, and negatively related to quantities of long-chain aliphatic C in the soil. The quantity of WSOC was positively related to the quantities of protein C, carbohydrate C, and negatively related to the quantity of carboxylic C. The quantity of soil MBC was not only related to quantities of soil WSOC but also to the quality of soil WSOC.
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    URL: http://dx.doi.org/10.1007/s003740050348
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    Microbial contribution to extractable N and P after air-drying of dry tropical soils (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 31-34 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass ; Air-drying ; Extractable ; nitrogen ; Extractable phosphorus ; Tropical soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The microbial contribution to extractable N and P after the air-drying of eight Indian dry tropical Ultisols was quantified. Air-drying of the soils decreased microbial biomass C by 25–53% but increased extractable N and P by 14–34% and 24–121%, respectively. This increase in the extractable N and P was accounted for, to some extent, by microbial biomass killed due to air-drying. Microbial biomass contributes 17–36% and 19–82% to the extractable N and P, respectively, possibly due to air-drying of the soils. I conclude that due to contamination of microbial biomass with the available nutrients in air-dried soils, measurements of extractable nutrients should be made on field-moist soils.
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    URL: http://dx.doi.org/10.1007/s003740050339
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    Cost-Effective Nutrient Reductions to the Baltic Sea (1997)
    Springer
    Environmental and resource economics 10 (1997), S. 341-362 
    Details
    ISSN: 1573-1502
    Keywords: Baltic Sea ; eutrophication ; nitrogen ; phosphorus ; cost effective
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Due to eutrophication caused by heavy loads of nitrogen and phosphorus, the biological conditions of the Baltic Sea have been disturbed: large sea bottom areas without any biological life, low stocks of cods, and toxic blue green algaes. It is recognized that the nitrogen and phosphorus loads to the Baltic Sea must be reduced by 50% in order to restore the sea. The main purpose of this paper is to calculate cost effective nitrogen and phosphorus reductions to the Baltic Sea from the nine countries surrounding the Baltic Sea. The results show a significant difference in minimum costs of decreasing nitrogen and phosphorus loads to the Sea: approximately 12 000 millions of SEK per year and 3 000 millions of SEK respectively for reductions by 50%. It is also shown that a change from a policy of cost-effective nutrient reductions to a policy where each country reduces the nutrient loads by 50% increase total costs for both nitrogen and phosphorus reductions by about 300%. The results are, however, sensitive to several of the underlying assumptions and should therefore be interpreted with much caution.
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    URL: http://dx.doi.org/10.1023/A:1026497515871
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    Sediment Accumulation of Nutrients (N, P) in the Eastern Gulf of Finland (Baltic Sea) (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 477-486 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; nitrogen ; phosphorus ; organic matter ; cluster analysis ; Gulf of Finland ; estuaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Dry weight (DW), ignition loss (IL) and concentrations of total nitrogen (TN) and total phosphorus (TP) of the sediment surface layer (0 to 10 cm, 1 cm slices) were analyzed from 20 sites in the eastern Gulf of Finland. The distance of the sampling sites from the mouth of the River Neva explained the nutrient concentrations of the sediments well, while the effect of water depth was negligible. The increase of TN and the decrease of TP along the transect from the river mouth towards the open Gulf were caused by the diminishing share of allochthonous material supplied from the River Neva. The mean TN concentration of the different accumulation areas was about 40 % higher in the sediment surface than in the deeper layer (9 to 10 cm). The corresponding difference for TP varied from 53 to 56 %. The results suggest considerable netflux of nutrients from sediment to water. The net sediment accumulation of nutrients were estimated as 6.0 g m-2 a-1 of N and 1.7 g m-2 a-1 of P corresponding 22 000 t a-1 of N and 6 100 t a-1 of P for the whole eastern Gulf.
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    Benthic fluxes of dissolved inorganic carbon, nutrients and oxygen in the Gulf of Trieste (Northern Adriatic) (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 305-314 
    Details
    ISSN: 1573-2932
    Keywords: Adriatic Sea ; nutrients ; benthic fluxes ; carbon ; nitrogen ; silicon ; phosphorus ; budgets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Benthic fluxes of dissolved inorganic N, Si and P nutrients, alkalinity, dissolved inorganic C (DIC), and O2 from sediments in the Gulf of Trieste (northern Adriatic, Italy) were measured monthly in the period September 1995 – August 1996 using in situ incubated light benthic chambers. The highest efluxes of DIC, NH4 +, PO4 3−, Si(OH)4, and NO3 − influxes encountered in late summer — early autumn were the consequence of degradation of benthic microalgae, and in autumn mostly of sedimented phytoplankton. High NO3 − efflux was observed in spring. Only NH4 + and Si(OH)4 fluxes were significantly correlated with temperature. This correlation suggests that the rate of downward input and the quality and quantity of sedimentary organic matter (autochthonous and allochthonous) were superimposed on the temperature fluctuations. High DIC, NH4 + and Si(OH)4 effluxes observed in July 1996 were due to the late spring — early summer degradation of sedimentary organic matter produced by benthic microalgae, while the autumn phytoplankton bloom was quickly reflected in enhanced benthic fluxes due to higher temperature. Significant correlations between NH4 +, PO4 3− and Si(OH)4 fluxes suggested their parallel regeneration and utilization at the sediment-water interface. The nutrient fluxes were linked to O2 consumption, suggesting that aerobic oxidation processes were important at the sediment-water interface in the Gulf. The N, P and Si nutrients released from sediment pore waters are probably utilized in benthic microalgal and bottom-water primary production. This indicates that pelagic and benthic communities in the central part of the Gulf of Trieste function relatively independently of each other.
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    URL: http://dx.doi.org/10.1007/BF02406870
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    LONG-TERM TRANSFORMATIONS AND REDISTRIBUTION OF POTENTIALLY TOXIC HEAVY METALS IN ARID-ZONE SOILS INCUBATED: I. UNDER SATURATED CONDITIONS (1997)
    Springer
    Water, air & soil pollution 95 (1997), S. 399-423 
    Details
    ISSN: 1573-2932
    Keywords: fractionation ; redistribution ; saturation ; kinetics ; heavy metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Solid-phase transformations of Cd, Cu, Cr, Ni and Zn, added as soluble salts at several levels to two arid-zone soils, were studied over a period of one year. The soils were maintained under a saturated-paste regime and sampled periodically. A selective sequential dissolution procedure was employed to determine the changes in metal distribution among six operationally defined solid-phase fractions. A function, Uts was introduced to measure the fractional attainment of equilibrium of the soils following a perturbation. The direction and rate of redistribution of the added metals in the soils were affected by the nature of the metal, the soil properties and the metal loading level. Cd added to the soils was transferred from the exchangeable (EXC) into the carbonate (CARB) fraction. When soluble Cu, Cr, Ni and Zn were added at low loading levels, metals were transferred from the reducible oxides(RO) bound and easily reducible oxides (ERO) bound fractions and the EXC fraction, into the CARB fraction. However, at the higher loading level, metals were transferred from the EXC and CARB fractions into the organic matter bound (OM), ERO and RO fractions. The Uts function approached lower values as incubation continued but remained removed from 1. The overall flux of metals among fractions was the combined result of the readjustment of the metals in the native soil to changing conditions due to saturation, and the transfer of added soluble metals to the less labile fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026450118082
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  • 93
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    Monitoring nitrogen pollution from sugarcane runoff using15N analysis (1997)
    Springer
    Water, air & soil pollution 98 (1997), S. 389-399 
    Details
    ISSN: 1573-2932
    Keywords: fertilizer ; nitrogen ; pollution ; runoff ; stable isotopes ; sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In many forested wetlands of Louisiana, surface water quality is being deteriorated by nutrient input from adjacent agricultural production area. This field study assesses the input of fertilizer N, applied to sugarcane fields, to forested wetlands. The potential use of natural abundance variations in15N/14N ratios for identification and tracing surface water N sources (NH 4 + - and NO 3 − -N) was evaluated. Runoff and surface water samples were collected from sugarcane fields and bordering forested wetlands (6 stations) over a 16 month period and analyzed for NH 4 + -N, NO 3 − -N, and associated NH 4 + -δ 15N and NO 3 − -δ 15N ratios. FertilizerN draining into adjacent forested wetland was estimated to be only a small fraction of the amount applied. Concentrations of NH 4 + - and NO 3 − -N in the collected water samples were low and ranged from 0.02 to 1.79 mg L−1. Isotopic analysis revealed NH 4 + -δ 15N and NO 3 − -δ 15N means were distinctive and may have the potential to be used as tracers of N contamination. The mean NH 4 + -δ 15N value was +18.6±7.1‰ and the NO 3 − -δ 15N mean was +8.3±3.1‰. Anomalously high NO 3 − -δ 15N values (〉30‰) were attributed to denitrification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02047046
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  • 94
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    Estimating the area affected by phosphorus runoff in an Everglades wetland: a comparison of universal kriging and Bayesian kriging (1997)
    Springer
    Environmental and ecological statistics 4 (1997), S. 1-29 
    Details
    ISSN: 1573-3009
    Keywords: geostatistics ; nutrients ; soils ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Phosphorus-enriched agriculture runoff is believed to be the leading cause of ecosystem changes of Everglades wetlands. To study this effect, it is necessary to estimate the area of the affected region. In this study, Bayesian kriging and universal kriging were used to estimate the area by analysing the data collected by Reddy et al. (1991). The background level of the soil's total phosphorus concentration is usedto determine whether the region is affected by the agriculture runoff, through an indicator function. The area of the affected region was represented by the integration of the indicator function over the entire wetland. The expected value of the affected area was calculated using the results derived from Bayesian and universal kriging. The outcome indicates that universal kriging is sensitive to specification of thecovariance model. It was observed that universal kriging and Bayesian kriging yield comparable results, if the specified covariance structures are of similar nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018503923695
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  • 95
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    Assessing the risk of soil contamination in the Swiss Jura using indicator geostatistics (1997)
    Springer
    Environmental and ecological statistics 4 (1997), S. 49-64 
    Details
    ISSN: 1573-3009
    Keywords: soil ; pollution ; threshold ; geostatistics ; indicators ; kriging ; risk ; Swiss Jura
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The probability that the concentrations of toxic substances in soil or other medium exceed tolerablemaxima at any unsampled place can be estimated by indicator geostatistics. The method is developed and used to estimate and map the risk of contamination by cadmium, copper and lead in the topsoil of a 14.5 km 2 region in the Swiss Jura. It combines both direct measurements of metal concentrations and thecalibration of a geological map, and it shows that the risk of toxicity is least on Argovian rocks. Two approaches are proposed to divide a region into safe' and 'hazardous' zones on the basis of probability maps. The first declares as contaminated all places where the risk of contamination exceeds a given threshold. The second approach first evaluates the financial costs that might result from a wrongdeclaration, after which the site is allocated to a class so as to minimize that cost. The risk of exposure for humans and animals is generally greater for contaminated agricultural land than for forest soil, and so land use is taken into account in both procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018505924603
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  • 96
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    Echelon approach to areas of concern in synoptic regional monitoring (1997)
    Springer
    Environmental and ecological statistics 4 (1997), S. 131-152 
    Details
    ISSN: 1573-3009
    Keywords: biodiversity ; geographic information systems ; geostatistics ; monitoring ; response surfaces ; spatial analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Echelons provide an objective approach to prospecting for areas of potential concern in synoptic regional monitoring of a surface variable. Echelons can be regarded informally as stacked hill forms. The strategy is to identify regions of the surface which are elevated relative to surroundings (Relative ELEVATIONS or RELEVATIONS). These are areas which would continue to expand as islands with receding (virtual) floodwaters. Levels where islands would merge are critical elevations which delimit echelons in the vertical dimension. Families of echelons consist of surface sectors constituting separate islands for deeper waters that merge as water level declines. Pits which would hold water are disregarded in such a progression, but a complementary analysis of pits is obtained using the surface as a virtual mould to cast a counter-surface (bathymetric analysis). An echelon tree is a family tree of echelons with peaks as terminals and the lowest level as root. An echelon tree thus provides a dendrogram representation of surface topology which enables graph theoretic analysis and comparison of surface structures. Echelon top view maps show echelon cover sectors on the base plane. An echelon table summarizes characteristics of echelons as instances or cases of hill form surface structure. Determination of echelons requires only ordinal strength for the surface variable, and is thus appropriate for environmental indices as well as measurements. Since echelons are inherent in a surface rather than perceptual, they provide a basis for computer-intelligent understanding of surfaces. Echelons are given for broad-scale mammalian species richness in Pennsylvania.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018518327329
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  • 97
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    Ammonia volatilization from a seasonally and spatially variable grazed grassland: Yellowstone National Park (1997)
    Springer
    Biogeochemistry 36 (1997), S. 189-203 
    Details
    ISSN: 1573-515X
    Keywords: ammonia volatilization ; grassland ; nitrogen ; ungulate ; Yellowstone National Park
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured ammonia volatilization at three topographic positions(hilltop, mid-slope, slope-bottom) on three grassland landscapes at threetimes during 1995 (April, May, July) on the northern winter range ofYellowstone National Park that supports large herds of native ungulates.Percent ammonia-N lost from all sites during the study ranged 1–24%of urea-N applied. Volatilization among sites was negatively related tosoil cation-exchange capacity (r = –0.85) and rates were highest inJuly. We used the relationship between soil CEC and percent Nvolatilized from urea-amended plots to estimate annual ammonia-Nvolatilization from 5 sites for which annual ungulate urine inputs werepreviously determined (Frank et al. 1994). Estimated mean annualammonia-N volatilized from those sites was 1.4 kg/ha/yr, which wasless than a previously reported regional atmospheric deposition rate (2kg/ha/yr; Swank 1984). Results indicate the need to understand theinteraction between (1) spatially heterogeneous patterns of soilprocesses, and 2) nonuniform patterns of ungulate use of landscapes todetermine rates of ecosystem-level N-gaseous loss. Findings alsosuggest that ammonia-N volatilized from urine patches should not leadto a decline in soil N in this ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005705121160
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  • 98
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    Marine nitrogen: Phosphorus stoichiometry and the global N:P cycle (1997)
    Springer
    Biogeochemistry 37 (1997), S. 237-252 
    Details
    ISSN: 1573-515X
    Keywords: freshwater ; limitation ; marine ; nitrogen ; phosphorus ; ratio ; stoichiometry ; trace elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen supply is often assumed to limitmarine primary production. A global analysis of totalnitrogen (N) to phosphorus (P) molar ratios shows thattotal N:P is low (〈16:1) in some estuarine andcoastal ecosystems, but up to 100:1 in open oceans.This implies that elements other than N may limitmarine production, except in human impacted, estuarineor coastal ecosystems. This pattern may reconcileconflicting enrichment studies, because N additionfrequently increases phytoplankton growth where totalN:P is expected to be low, but P, Fe, or Si augmentphytoplankton growth in waters where total N:P ishigh. Comparison of total N:P stoichiometry betweenmarine and freshwaters yields a model of the form ofthe aquatic N:P cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005712322036
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  • 99
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    Concentrations and controls of dissolved organic matter in a constricted-channel region of the Ohio River (1997)
    Springer
    Biogeochemistry 38 (1997), S. 41-65 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; nitrogen ; Ohio River ; phosphorus ; Red field ratios ; dissolved organic matter ; rivers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A 12-month study was conducted to measure the concentrations ofdissolved organic matter (DOC, TDN, TDP) in four sites within a119 km long reach of the Ohio River, near Louisville, KY. In thisstudy we test whether specific geomorphological and biologicalfactors influenced variations in dissolved organic matter.Concentrations of DOC in the river averaged ≈1200μmol/L, and varied by nearly two orders of magnitudeseasonally (mean DOC during base flow ≈620 μmol/L).Peak periods for DOC at all sites were during April–May. Thesite nearest a navigation dam (deeper, lower current velocities)had significantly lower concentrations of TDN and greater C:Nratios than upstream sites. The largest tributary entering thisreach (Kentucky River) had no significant effect on levels of DOMin the main river, despite having significantly greaterconcentrations of TDN and lower levels of DOC during most monthsof the year. Concentrations of DOC, TDN, and TDP were notsignificantly different in littoral and pelagic habitats at allsites studied, suggesting little floodplain influence on DOM inthis constricted-channel section of the Ohio River. C:N ratios ofDOM in the Ohio were significantly different among seasons; C:Nexceeded or equaled Redfield ratios in summer and fall (6 to 10),but were below Redfield (1.8 to 3.0) during winter and spring.Regression models suggest that total phytoplankton densities andflow conditions are the two most important factors regulating DOMin this very large river.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005708326368
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  • 100
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    Solute dynamics in soil water and groundwater in a central Amazon catchment undergoing deforestation (1997)
    Springer
    Biogeochemistry 38 (1997), S. 303-335 
    Details
    ISSN: 1573-515X
    Keywords: Amazon ; deforestation ; hydrologic pathway ; groundwater ; nitrogen ; rain forest ; slash-and-burn agriculture ; solutes ; tropical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Hydrochemical changes caused by slash-and-burnagricultural practices in a small upland catchment inthe central Amazon were measured. Soluteconcentrations were analyzed in wet deposition,overland flow, shallow throughflow, groundwater andbank seepage in a forested plot (about 5 ha) and anadjacent plot (about 2 ha) which had been deforestedin July 1989 and planted to manioc, and in streamwater in partially deforested and forested catchments. Measurements were made from November 1988 to June1990. The effects of slash-and-burn agriculturalpractices observed in the experimental plot includedincreased overland flow, erosion, and large losses ofsolutes from the rooted zone. Concentrations ofNO3 -, Na+, K+, SO4 2-,Cl- and Mn in throughflow of the experimentalplot were higher than those of the control plot bymore than a factor of 10. Extensive leaching occurredafter cutting and burning, but solute transfers werediminished along pathway stages of throughflow togroundwater, and particularly within the riparian zoneof the catchment. High concentrations of N and P inoverland flow indicate the importance of usingforested riparian buffers to mitigate solute inputs toreceiving waters in tropical catchments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005801303639
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