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  • 1
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    Using continuous electrical conductivity measurements to derive major solute concentrations in karst systems (2023)
    John Wiley & Sons, Inc. | Hoboken, USA
    Details
    Publication Date: 2024-05-23
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Hydrochemical data of karst springs provide valuable insights into the internal hydrodynamical functioning of karst systems and support model structure identification. However, the collection of high‐frequency time series of major solute species is limited by analysis costs. In this study, we develop a method to retrieve the individual solute concentration time series and their uncertainty at high temporal resolution for karst springs by using continuous observations of electrical conductivity (EC) and low‐frequency ionic measurements. Due to the large ion content and non‐negligible concentrations of aqueous complexes in karst systems, the concentration of each solute species occurring as free ion and as part of aqueous complexes are computed separately. The concentration of species occurring as free ions are computed considering their contributions to the total EC, whereas the concentration of the species as part of complexes are obtained from speciation calculations. The pivotal role of the complexation processes for the reconstruction of solute concentration time series starting from the EC signal is investigated in two karstic catchments with different geologies and temporal resolution of the available hydrochemical datasets, that is the Kerschbaum dolostone system in Austria and the Baget limestone system in France. The results show that complexation processes are significant and should be considered for the estimation of the total solute concentration in case of SO〈sub〉4〈/sub〉, Ca, Mg and HCO〈sub〉3〈/sub〉. The EC signal of a karst spring can be used to interpolate and quantify the dynamics of those solutes characterized by large contribution (approximately >6%) to the total EC and low relative variability, that is HCO〈sub〉3〈/sub〉, Ca and Mg. Moreover, the presented method can be used to estimate concentrations of solutes when applied to karst systems with stationary and hydrogeochemical homogeneous contributing area. On the contrary, the method is affected by large uncertainty in case of dynamic systems characterized by varying contributions of water from different geological areas. This study aims to contribute to the problem of hydrogeochemical data availability and to support future works on karst systems conceptualization.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: École Polytechnique Fédérale de Lausanne http://dx.doi.org/10.13039/501100001703
    Description: European Regional Development Fund http://dx.doi.org/10.13039/501100008530
    Description: http://www.hydroshare.org/resource/fb92daaffced415fb7a991747e73adfa
    Keywords: ddc:551.9 ; electrical conductivity decomposition ; high‐resolution hydrochemical data ; hydrochemical modelling ; karst
    Language: English
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  • 2
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    Mobilization of Tungsten in Greenstone Belts of the Archean Kaapvaal and Singhbhum Cratons (2023)
    Details
    Publication Date: 2024-05-22
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Due to the inherently fluid‐mobile nature of W, the 〈sup〉182〈/sup〉W record of the early Earth may have been obscured by fluid‐induced mobilization of W. To investigate W mobilization in Archean greenstone sequences, we analyzed 〈sup〉182〈/sup〉W isotope systematics and major and trace element concentrations in samples from the 3.53 Ga old Onverwacht Group of the Kaapvaal Craton (South Africa) and the >3.51 Ga old Badampahar Group of the Singhbhum Craton (India). Our results for mafic and ultramafic metavolcanic rocks show W/Th ratios significantly higher than primary magmatic values, which suggests fluid‐induced W enrichment. Samples least affected by secondary W enrichment (W/Th 〈 0.26) show no resolvable W isotope anomalies from modern mantle values in both cratons. Samples from the Kaapvaal Craton with elevated W/Th exhibit deficits in 〈sup〉182〈/sup〉W as low as −8.1 ± 4.3 ppm compared to the modern mantle. Covariations of μ〈sup〉182〈/sup〉W with W/Th, and Ce/Pb suggest that negative isotope signatures were introduced during secondary fluid‐mediated processes. The enrichment of W is most evident in altered ultramafic rocks comprising serpentine, resulting in additional covariations between MgO, LOI, and W/Th. The W isotope composition of serpentinized komatiites reflects the composition of younger intruding granitoids. We therefore infer the latter as a possible source of W‐rich fluids. The Badampahar Group samples exhibit little W isotope variability. A well‐resolved 〈sup〉182〈/sup〉W deficit of −6.2 ± 2.9 ppm was determined in a single komatiite sample, which indicates an unknown fluid source, currently not represented in any other unit of the Singhbhum Craton.〈/p〉
    Description: Plain Language Summary: The tungsten (W) isotope composition of ancient rocks can be used to trace processes that occurred during Earth's early evolution. However, interactions between rocks and fluids may alter the W concentration and therefore influence the interpretation of W isotope data. To identify the source of such fluids and the processes by which they affect the W isotope composition of rocks, we analyzed ancient rock samples from South Africa and India. The isotope composition of rocks with a low W concentration reflects that of the modern Earth. Therefore, they do not trace the processes that occurred during Earth's early evolution. Samples from South Africa with untypically high W concentrations show a different isotopic composition. The variation in the W isotope signature correlates with other chemical indices that are susceptible to modification by fluid‐related processes. This shows that the W within the rocks is derived from an external fluid source and not from their original magmatic source. Samples with the highest W enrichment have a similar isotope composition as spatially associated intrusive rocks. By inference, the latter likely represent the source of W‐rich fluids. The samples from India show similar enrichment in W, indicating similar fluid‐related processes and W sources at both localities.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉The magmatic sources of metavolcanic rocks from the Onverwacht Group and the Badampahar Group do not exhibit W isotope anomalies〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Negative W isotope signatures in the Onverwacht Group are likely derived from fluids sourced from younger intrusive granitoids〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Felsic intrusive rocks are a major source of W‐rich fluids in Paleoarchean greenstone units〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://doi.org/10.5880/digis.2023.005
    Keywords: ddc:551.9 ; fluid‐mobility ; Kaapvaal ; Singhbhum ; 182W ; tungsten isotopes
    Language: English
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  • 3
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    Zircon Dates Long‐Lived Plume Dynamics in Oceanic Islands (2022)
    Details
    Publication Date: 2024-04-25
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉In this contribution we report the first systematic study of zircon U‐Pb geochronology and δ〈sup〉18〈/sup〉O‐〈italic〉ε〈/italic〉Hf〈sub〉(〈italic〉t〈/italic〉)〈/sub〉 isotope geochemistry from 10 islands of the hot‐spot related Galapagos Archipelago. The data extracted from the zircons allow them to be grouped into three types: (a) young zircons (0–∼4 Ma) with 〈italic〉ε〈/italic〉Hf〈sub〉(〈italic〉t〈/italic〉)〈/sub〉 (∼5–13) and δ〈sup〉18〈/sup〉O (∼4–7) isotopic mantle signature with crystallization ages dating the islands, (b) zircons with 〈italic〉ε〈/italic〉Hf〈sub〉(〈italic〉t〈/italic〉)〈/sub〉 (∼5–13) and δ〈sup〉18〈/sup〉O (∼5–7) isotopic mantle signature (∼4–164 Ma) which are interpreted to date the time of plume activity below the islands (∼164 Ma is the minimum time of impingement of the plume below the lithosphere), and (c) very old zircons (∼213–3,000 Ma) with mostly continental (but also juvenile) 〈italic〉ε〈/italic〉Hf〈sub〉(〈italic〉t〈/italic〉)〈/sub〉 (∼−28–8) and δ〈sup〉18〈/sup〉O (∼5–11) isotopic values documenting potential contamination from a number of sources. The first two types with similar isotopic mantle signature define what we call the Galápagos Plume Array (GPA). Given lithospheric plate motion, this result implies that GPA zircon predating the Galápagos lithosphere (i.e., >14–164 Ma) formed and were stored at sublithospheric depths for extended periods of time. In order to explain these observations, we performed 2D and 3D thermo‐mechanical numerical experiments of plume‐lithosphere interaction which show that dynamic plume activity gives rise to complex asthenospheric flow patterns and results in distinct long‐lasting mantle domains beneath a moving lithosphere. This demonstrates that it is physically plausible that old plume‐derived zircons survive at asthenospheric depths below ocean islands.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Our data define the Galápagos Plume Array defined by mantle 〈italic〉ε〈/italic〉Hf〈sub〉(〈italic〉t〈/italic〉)〈/sub〉 and δ18O values in the range ∼0–164 Ma〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉This finding allows dating back plume activity to, at least, early Middle Jurassic (∼164 Ma)〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Numerical experiments confirm it is plausible that old Plume‐derived zircons survive in the asthenosphere for extended periods of time〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Ministerio de Asuntos Económicos y Transformación Digital, Gobierno de España http://dx.doi.org/10.13039/501100010198
    Description: Ministerio de Ciencia e Innovación http://dx.doi.org/10.13039/501100004837
    Description: European Research Council http://dx.doi.org/10.13039/501100000781
    Description: https://doi.org/10.5281/zenodo.7047729
    Description: https://doi.org/10.5281/zenodo.6967187
    Keywords: ddc:551.9 ; mantle plume ; galapagos zircon ages ; asthenospheric zircon ; oceanic islands ; thermo‐mechanical numerical experiments
    Language: English
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  • 4
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    Zur Geochemie von Migmatiten (1980)
    Berlin: Reimer
    In:  Herausgeberexemplar
    Details
    Publication Date: 2024-04-18
    Description: Anatektische Schmelzen haben bei der Entstehung granitischer bis dioritischer Magmen in der Erdkruste eine entscheidende Bedeutung. Die große Tiefe und breite Ausdehnung, in der sich sialische Granitisations-Prozesse vollziehen, bedingen aber auch die Seltenheit ihres Aufschlusses an der Erdoberfläche. An Stelle dieser Übergänge metamorph -〉 magmatisch in situ (ERDMANNSDÖRFFER, 1948) wurden daher stets die wesentlich kleinräumigeren Erscheinungen in Migmatiten untersucht. Man ging dabei von der Voraussetzung aus, daß diese als "Modell Systeme" anzusehen sind (MEHNERT, 1968/71). Die meisten geochemischen Untersuchungen zu diesem Thema berücksichtigten bisher nur die Hauptelemente. Angaben über Spurenelement-Konzentrationen basieren meist nur auf wenigen Einzelanalysen. Als Grundlage der hier vorgelegten Zusammenfassung geochemischer Daten zur Migmatitgenese dienten im wesentlichen die petrologischen Untersuchungen anatektischer Gesteine von MEHNERT und von BÜSCH (Zitate im Text). Diese Basis wurde durch Hinzunahme von neueren Literaturdaten erweitert. Die Analyse einer möglichst großen Anzahl von Einzelproben von Gneisen, Leukosomen und Melanosomen auf Haupt-, Neben- und Spurenelemente und die Berücksichtigung der Auswirkungen der Streuungen erbrachte neue Erkenntnisse…
    Description: thesis
    Description: DFG, SUB Göttingen
    Keywords: ddc:552.4 ; ddc:551.9 ; Geochemie ; Migmatit ; Schwarzwald
    Language: German
    Type: doc-type:book
    Format: 82
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  • 5
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    Geochemie und Metamorphose der Amphibole der Sesia-Lanzo-Zone nordöstlich des Val d'Ossola, Provincia di Novara/Norditalien (1991)
    Details
    Publication Date: 2024-04-09
    Description: Chemische und optische Analysen von Amphibolen der Sesia-Lanzo-Zone, nordöstlich des Val d'Ossola, Norditalien, bezeugen fünf verschiedene Amphibol-Serien, die sich vier verschiedenen Metamorphose-Ereignissen zuordnen lassen. Sowohl eine hochtemperierte präalpine Generation als auch die beiden alpinen Generationen zeigen, anhand ihrer chemischen Entwicklung, von Südosten nach Nordwesten steigende metamorphe Bedingungen an. Obwohl in anderen Gebieten nachweisbar, läßt sich eine Hochdruckparagenese in dem bearbeiteten Gebiet nicht belegen.
    Description: Abstract: Chemical and optical analyses for amphiboles of the Sesia-Lanzo Zone NEof the Val d'Ossola, Northern Italy, reveal five different Ca-amphibole series of two Alpine and two pre-Alpine metamorphic episodes. At least the three youngest display prograde evolution from SE to NW. The early Alpine high pressure mineral paragenesis, which is typical for the Sesia-Lanzo Zone Southwest of the studied area, is appararently absent in this region.
    Description: research
    Keywords: ddc:551.9 ; Geochemie ; Metamorphose ; Amphibole ; Italien
    Language: German
    Type: doc-type:article , publishedVersion
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  • 6
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    Groundwater fluoride contamination in Coimbatore district: a geochemical characterization, multivariate analysis, and human health risk perspective (2021)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2024-04-02
    Description: In this paper, fluoride geochemistry and health risk of groundwater in Coimbatore district is studied. The order of dominance of ions were HCO〈sub〉3〈/sub〉 〉 Cl 〉 SO〈sub〉4〈/sub〉 〉 CO〈sub〉3〈/sub〉 and Na 〉 Ca 〉 Mg 〉 K. Alkaline groundwater and the dominance of HCO〈sub〉3〈/sub〉 and Na is favourable for the fluoride enrichment. Around 46% of the samples, N–NE regions, have F〈sup〉−〈/sup〉 higher than permissible limit of 1.5 mg/L. Pink granites, charnockite and gneisses in lithology is the possible origin of F〈sup〉−〈/sup〉. However, NO〈sub〉3〈/sub〉 vs F plot shows positive trend in some samples, indicating anthropogenic inputs of F〈sup〉−〈/sup〉. Correlation plots of F〈sup〉−〈/sup〉 was trending positive with pH, HCO〈sub〉3〈/sub〉 and Na and but negative for Ca, indicating the control of these ions in F〈sup〉−〈/sup〉 mobility. This result is supported by undersaturation of fluorite and supersaturation of carbonates. Four significant principal components were derived, which have explained 87% of the total variation. PC1 has high factor loadings for EC, Ca, Mg Na, Cl, SO〈sub〉4〈/sub〉, NO〈sub〉3〈/sub〉 indicating both natural and anthropogenic influences. PC2, PC3 and PC4 have higher loading for pH and HCO〈sub〉3〈/sub〉, K and HCO〈sub〉3〈/sub〉 and F〈sup〉−〈/sup〉, respectively, indicating geogenic factors in the F〈sup〉−〈/sup〉 enrichment. Human health risk assessment (HHRA) by ingestion and dermal pathways were calculated using Hazard Quotient HQ and Hazard Index (HI). 27% of males, 36% of females and 39% of the children have HI 〉 1, posing noncarcinogenic risks.
    Description: Freie Universität Berlin (1008)
    Keywords: ddc:551.9 ; Fluoride ; Geochemistry ; Multivariate analysis ; Human health risk assessment (HHRA) ; Revised permissible limits ; Coimbatore
    Language: English
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  • 7
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    Dissolved, Labile, and Total Particulate Trace Metal Dynamics on the Northeast Greenland Shelf (2022)
    Chen, Xue‐Gang ; Krisch, Stephan ; Al‐Hashem, Ali ; [et al.]
    Details
    Publication Date: 2024-03-22
    Description: We present high‐resolution profiles of dissolved, labile, and total particulate trace metals (TMs) on the Northeast Greenland shelf from GEOTRACES cruise GN05 in August 2016. Combined with radium isotopes, stable oxygen isotopes, and noble gas measurements, elemental distributions suggest that TM dynamics were mainly regulated by the mixing between North Atlantic‐derived Intermediate Water, enriched in labile particulate TMs (LpTMs), and Arctic surface waters, enriched in Siberian shelf‐derived dissolved TMs (dTMs; Co, Cu, Fe, Mn, and Ni) carried by the Transpolar Drift. These two distinct sources were delineated by salinity‐dependent variations of dTM and LpTM concentrations and the proportion of dTMs relative to the total dissolved and labile particulate ratios. Locally produced meltwater from the Nioghalvfjerdsbræ (79NG) glacier cavity, distinguished from other freshwater sources using helium excess, contributed a large pool of dTMs to the shelf inventory. Localized peaks in labile and total particulate Cd, Co, Fe, Mn, Ni, Cu, Al, V, and Ti in the cavity outflow, however, were not directly contributed by submarine melting. Instead, these particulate TMs were mainly supplied by the re‐suspension of cavity sediment particles. Currently, Arctic Ocean outflows are the most important source of dFe, dCu, and dNi on the shelf, while LpTMs and up to 60% of dMn and dCo are mainly supplied by subglacial discharge from the 79NG cavity. Therefore, changes in the cavity‐overturning dynamics of 79NG induced by glacial retreat, and alterations in the transport of Siberian shelf‐derived materials with the Transport Drift may shift the shelf dTM‐LpTM stoichiometry in the future.
    Description: Plain Language Summary: Trace metals (TMs) including cobalt (Co), iron (Fe), manganese (Mn), copper (Cu), and nickel (Ni) are essential micronutrients for marine productivity. The Northeast Greenland shelf is a climatically sensitive region, influenced by both outflowing Arctic waters and local glacier melting. We lack knowledge on how these Arctic surface waters affect TM dynamics on the Greenland shelf and how climatic shifts may influence TM dynamics. Here, we distinguish local submarine meltwater from Arctic surface waters using distinct tracers; noble gases and radium isotopes. We show that the TM dynamics on the shelf are largely controlled by the intrusion of Arctic surface waters which creates a near‐surface plume of dissolved and labile particulate TMs. Conversely, submarine meltwater creates a subsurface plume enriched in dissolved TMs but depleted in particulate TMs, which is exported from underneath a floating ice tongue. In the future, increasing Arctic river discharge and local glacial melting may both significantly change shelf micronutrient ratios demonstrating downstream impacts of a changing cryosphere on marine biogeochemical cycles.
    Description: Key Points: The overall dissolved and particulate trace metal (TM) dynamics were mainly regulated by the mixing with Arctic surface waters. Resuspension of cavity sediments is a major localized source of labile and total particulate Cd, Co, Fe, Mn, Ni, Cu, Al, V, and Ti. Whilst dissolved and particulate TMs are mostly coupled on the Greenland shelf, cavity outflow decouples both phases.
    Description: Kuwait Institute for Scientific Research
    Description: Deutsche Forschungsgemeinschaft
    Description: https://doi.pangaea.de/10.1594/PANGAEA.871030
    Description: https://doi.pangaea.de/10.1594/PANGAEA.871030
    Description: https://doi.pangaea.de/10.1594/PANGAEA.871028
    Description: https://doi.pangaea.de/10.1594/PANGAEA.905347
    Description: https://doi.pangaea.de/10.1594/PANGAEA.933431
    Description: https://doi.pangaea.de/10.1594/PANGAEA.948466
    Description: https://doi.pangaea.de/10.1594/PANGAEA.936029
    Description: https://doi.pangaea.de/10.1594/PANGAEA.936027
    Description: https://doi.org/10.1594/PANGAEA.931336
    Keywords: ddc:551.9 ; Arctic ; trace metals ; labile particulate ; glacier ; meltwater ; GEOTRACES
    Language: English
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  • 8
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    Temperature Calibration of Elevated Mg/Ca in Planktic Foraminifera Shells From the Hypersaline Gulf of Aqaba (2023)
    Details
    Publication Date: 2024-02-21
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The Mg/Ca of marine calcareous Planktic Foraminifera (PF) shells is commonly used for sea surface temperature reconstructions. However, compared to open marine environments, hypersaline (>40) oligotrophic seas have been shown to accommodate PF with higher Mg/Ca and divergent temperature to Mg/Ca relationships. To investigate influencing factors of PF Mg uptake in hypersaline regions, we measured the Mg/Ca of two flux‐dominating PF species, 〈italic〉Globigerinoides ruber albus〈/italic〉 and 〈italic〉Turborotalita clarkei〈/italic〉, derived from a monthly resolved time series of sediment traps in the Gulf of Aqaba, northern Red Sea as well as the corresponding temperature, salinity, and 〈italic〉p〈/italic〉H values. The PF exhibit elevated Mg/Ca which cannot be explained by post‐deposition or interstitial sediment diagenetic processes. 〈italic〉G. ruber albus〈/italic〉 displays Mg/Ca trends that strongly follow seasonal mixed layer temperature changes. Conversely, 〈italic〉T〈/italic〉. 〈italic〉clarkei〈/italic〉 Mg/Ca trends do not follow temperature but rather show significant Mg/Ca enrichment following mixing of the surface water column. We present a framework for incorporating elevated Mg/Ca into global Mg/Ca‐T calibrations for 〈italic〉G〈/italic〉. 〈italic〉ruber albus〈/italic〉 and present a new Mg/Ca‐T calibration suitable for hypersaline marine environments.〈/p〉
    Description: Plain Language Summary: Past seawater temperature is reconstructed from the magnesium‐to‐calcium ratio (Mg/Ca) in the calcareous shells of a group of marine microplankton called foraminifera. Two foraminifer species, 〈italic〉Globigerinoides ruber albus〈/italic〉 and 〈italic〉Turborotalita clarkei〈/italic〉, are abundant in the Gulf of Aqaba, northern Red Sea, at year‐round high temperatures and salinities. The shells of these foraminifera have elevated Mg/Ca relative to other marine regions, and here, we explore the factors causing this. The Mg/Ca values of both 〈italic〉G〈/italic〉. 〈italic〉ruber albus〈/italic〉 and 〈italic〉T〈/italic〉. 〈italic〉clarkei〈/italic〉 reflect the environmental conditions of the water column. For 〈italic〉G〈/italic〉. 〈italic〉ruber albus〈/italic〉, temperature and salinity appear to be factors responsible for the Mg/Ca trends and elevated values. We incorporate the new Mg/Ca data for 〈italic〉G〈/italic〉. 〈italic〉ruber albus〈/italic〉 to calibrate elevated Mg/Ca with temperature for high‐salinity (>40) marine environments. The Mg/Ca of the deeper dwelling 〈italic〉T〈/italic〉. 〈italic〉clarkei〈/italic〉 show higher ratios following deep mixing of the surface water column and may indicate annually recurring phytoplankton blooms caused by nutrient input into the sunlit ocean surface.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉A new Mg/Ca temperature calibration for high salinity environments is presented for 〈italic〉Globigerinoides ruber albus〈/italic〉〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉A framework for incorporating high salinity environments into global Mg/Ca‐T calibrations is provided〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Enhanced Mg/Ca in subsurface dwelling 〈italic〉Turborotalita clarkei〈/italic〉 may indicate seasonal deep mixing of the upper water column〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Israel Science Foundation http://dx.doi.org/10.13039/501100003977
    Description: Minerva PhD Fellowship Stipend
    Description: Advance School for Environmental Studies
    Description: https://doi.org/10.1594/PANGAEA.959629
    Description: https://doi.org/10.17617/3.EXFQC2
    Keywords: ddc:551.9 ; Gulf of Aqaba ; Planktic Foraminifera shells ; Mg/Ca ; sea surface temperature reconstructions
    Language: English
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  • 9
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    Sulphate reduction determines the long-term effect of iron amendments on phosphorus retention in lake sediments (2021)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2024-01-12
    Description: Purpose: This field study aimed to guide the planning of iron amendments for phosphorus retention by investigating the long-term fate of iron added to two urban lakes (Plötzensee and Groß Glienicker See) in Berlin, Germany. The contributions of iron dosing to improve lake status as well as the relevance of competing processes for management success were evaluated. Methods: Sediment stratigraphy, as well as occurrence of iron minerals, and fluxes between water and sediment were examined using geochemical analyses (i.e. element composition, sequential extraction, X-ray diffraction, and pore water analyses). A one-box lake model was used to relate these fluxes to monitoring data from the water column and to sediment inventories. Results: In both lakes, the added iron was preserved in the sediment. Whereas phosphorus retention increased following the addition of iron to Groß Glienicker See, sulphur was retained by the excess iron in Plötzensee. This contrasting effect is attributed to significantly different sulphate reduction rates in two lakes (Wilcoxon rank sum test: W = 25, p = 0.008). According to the one-box model, sulphate reduction explained both the decrease in measured sulphate concentrations after iron application as well as the observed increase in sulphur deposition in the sediments. Conclusion: Management interventions involving iron amendments to enhance phosphorus retention must consider the competing process of iron sulphide formation during the entire management plan period, and additional iron may need to be applied to account for this effect.
    Description: Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB) im Forschungsverbund Berlin e.V. (3473)
    Keywords: ddc:551.9 ; Iron dosing ; Lake restoration ; Management implications ; Minerals ; Sulphur cycling ; Long-term field study ; One-box model
    Language: English
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  • 10
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    Bioavailable DOC: reactive nutrient ratios control heterotrophic nutrient assimilation—An experimental proof of the macronutrient-access hypothesis (2021)
    Graeber, Daniel ; Tenzin, Youngdoung ; Stutter, Marc ; [et al.]
    Springer International Publishing
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    Publication Date: 2023-11-28
    Description: We investigate the "macronutrient-access hypothesis", which states that the balance between stoichiometric macronutrient demand and accessible macronutrients controls nutrient assimilation by aquatic heterotrophs. Within this hypothesis, we consider bioavailable dissolved organic carbon (bDOC), reactive nitrogen (N) and reactive phosphorus (P) to be the macronutrients accessible to heterotrophic assimilation. Here, reactive N and P are the sums of dissolved inorganic N (nitrate-N, nitrite-N, ammonium-N), soluble-reactive P (SRP), and bioavailable dissolved organic N (bDON) and P (bDOP). Previous data from various freshwaters suggests this hypothesis, yet clear experimental support is missing. We assessed this hypothesis in a proof-of-concept experiment for waters from four small agricultural streams. We used seven different bDOC:reactive N and bDOC:reactive P ratios, induced by seven levels of alder leaf leachate addition. With these treatments and a stream-water specific bacterial inoculum, we conducted a 3-day experiment with three independent replicates per combination of stream water, treatment, and sampling occasion. Here, we extracted dissolved organic matter (DOM) fluorophores by measuring excitation-emission matrices with subsequent parallel factor decomposition (EEM-PARAFAC). We assessed the true bioavailability of DOC, DON, and the DOM fluorophores as the concentration difference between the beginning and end of each experiment. Subsequently, we calculated the bDOC and bDON concentrations based on the bioavailable EEM-PARAFAC fluorophores, and compared the calculated bDOC and bDON concentrations to their true bioavailability. Due to very low DOP concentrations, the DOP determination uncertainty was high, and we assumed DOP to be a negligible part of the reactive P. For bDOC and bDON, the true bioavailability measurements agreed with the same fractions calculated indirectly from bioavailable EEM-PARAFAC fluorophores (bDOC r〈sup〉2〈/sup〉 = 0.96, p 〈 0.001; bDON r〈sup〉2〈/sup〉 = 0.77, p 〈 0.001). Hence we could predict bDOC and bDON concentrations based on the EEM-PARAFAC fluorophores. The ratios of bDOC:reactive N (sum of bDON and DIN) and bDOC:reactive P (equal to SRP) exerted a strong, predictable stoichiometric control on reactive N and P uptake (R〈sup〉2〈/sup〉 = 0.80 and 0.83). To define zones of C:N:P (co-)limitation of heterotrophic assimilation, we used a novel ternary-plot approach combining our data with literature data on C:N:P ranges of bacterial biomass. Here, we found a zone of maximum reactive N uptake (C:N:P approx. 〉 114: 〈 9:1), reactive P uptake (C:N:P approx. 〉 170:21: 〈 1) and reactive N and P co-limitation of nutrient uptake (C:N:P approx. 〉 204:14:1). The “macronutrient-access hypothesis” links ecological stoichiometry and biogeochemistry, and may be of importance for nutrient uptake in many freshwater ecosystems. However, this experiment is only a starting point and this hypothesis needs to be corroborated by further experiments for more sites, by in-situ studies, and with different DOC sources.
    Description: Rural and Environment Science and Analytical Services Division http://dx.doi.org/10.13039/100011310
    Description: Helmholtz-Gemeinschaft http://dx.doi.org/10.13039/501100001656
    Description: Helmholtz-Zentrum für Umweltforschung GmbH - UFZ (4215)
    Keywords: ddc:551.9 ; Ecological stoichiometry ; Dissolved organic nitrogen ; PARAFAC ; Dissolved inorganic nitrogen ; Phosphate ; Ternary plots
    Language: English
    Type: doc-type:article
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