The main goal of this study is to analyze import, transfer, fate of PPCPs as trace pollutants in ... more The main goal of this study is to analyze import, transfer, fate of PPCPs as trace pollutants in situ and ex situ. This study attempts to examine the fate and transport of PPCPs in small fields using LC-ESI-MS/MS as a tool to monitor. In addition, transport and sorption of selected PPCPs in undisturbed soil columns will be evaluated with bromide tracer and HYDRUS software. Contribution of preferential flow and colloid-facilitated transport to the overall PPCPs movement to subsurface drain will also be featured in field studies and column experiments in this project. The output of this project will extend our knowledge of PPCPs and other emerging pollutants which are likely to affect organisms as well as human beings. Keyword: pharmaceuticals and personal care products (PPCPs), transport, monitoring, HYDRUS, LC-ESI-MS/MS, preferential flow, colloid-facilitated transport
From 1982 to 2001 acidic conditions prevailed at former lignite mining Lake Knappensee. Since 200... more From 1982 to 2001 acidic conditions prevailed at former lignite mining Lake Knappensee. Since 2001 the acidity of the lake water continuously decreased reaching circum-neutral pH conditions in 2010. Based on acidity time series of the lake water in combination with water budgets derived from a regional groundwater model the cumulative acidity loss in the lake for the time span from 2001 to 2015 can be estimated to be 8400 kmol. Internal neutralization by biogenic sulfate reduction with consecutive deposition of reduced sulfur in the lake sediment was supposed to be the crucial process leading to the observed decrease in lake water acidity. In order to test this hypothesis elaborate quantitative field and laboratory investigations were launched in December 2014. 15 sediment cores distributed over the lake`s area were sampled and analyzed for reduced sulfur species at the hydrological laboratory of the University of Bayreuth. The measured sulfur contents were converted into deposited ...
The Fe(II) monosulfide mineral mackinawite (FeS) is an important phase in low-temperature iron an... more The Fe(II) monosulfide mineral mackinawite (FeS) is an important phase in low-temperature iron and sulfur cycles, yet it is challenging to characterize since it often occurs in X-ray amorphous or nanoparticulate forms and is extremely sensitive to oxidation. Moreover, the electronic configuration of iron in mackinawite is still under debate. Mössbauer spectroscopy has the potential to distinguish mackinawite from other FeS phases and provide clarity on the electronic configuration, but conflicting results have been reported. We therefore conducted a Mössbauer study at 5 K of five samples of mackinawite synthesized through different pathways. Samples show two different Mössbauer patterns: a singlet that remains unsplit at all temperatures studied, and a sextet with a hyperfine magnetic field of 27(1) T at 5 K, or both. Our results suggest that the singlet corresponds to stoichiometric mackinawite (FeS), while the sextet corresponds to mackinawite with excess S (FeS1+x). Both phases s...
Agricultural non-point source (NPS) pollution is a major concern for water quality management in ... more Agricultural non-point source (NPS) pollution is a major concern for water quality management in the Soyang watershed in South Korea. Nutrients (phosphorus and nitrogen), organic matter, and sediment exports in streams were estimated in an agricultural catchment (Haean catchment) for two years. The stream water samples were taken in dry and rainy seasons to evaluate the effect of monsoonal rainfall on pollutants exports. The influence of land use changes on NPS pollution was assessed by conducting a land use census and comparing the NPS characteristic exports. Total phosphorus (TP), suspended solids (SS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) increased dramatically in rainy seasons. Land uses were changed during the study period. Dry fields and rice paddies have decreased distinctively while orchard (apple, grape, and peach) and ginseng crops showed an increase within the catchment. The TP and SS loading decreased in the streams in 2010 compared to the loading in 2009 while the BOD and NO 3 − did not show distinct significant change. In this study, monsoonal driven rainfalls increased exports of agricultural NPS pollutants into streams. Land use change (mostly crop and paddy fields to orchards and ginseng fields) remarkably mitigated TP and SS exports into the streams.
We investigated the microbial community compositions in two sediment samples from the acidic (pH ... more We investigated the microbial community compositions in two sediment samples from the acidic (pH ∼3) and hypersaline (>4.5% NaCl) surface waters, which are widespread in Western Australia. In West Dalyup River, large amounts of NaCl, Fe(II) and sulfate are brought by the groundwater into the surface runoff. The presence of K-jarosite and schwertmannite minerals in the river sediments suggested the occurrence of microbial Fe(II) oxidation because chemical oxidation is greatly reduced at low pH. 16S rRNA gene diversity analyses revealed that sequences affiliated with an uncultured archaeal lineage named Aplasma, which has the genomic potential for Fe(II) oxidation, were dominant in both sediment samples. The acidophilic heterotrophs Acidiphilium and Acidocella were identified as the dominant bacterial groups. Acidiphilium strain AusYE3-1 obtained from the river sediment tolerated up to 6% NaCl at pH 3 under oxic conditions and cells of strain AusYE3-1 reduced the effects of high salt content by forming filamentous structure clumping as aggregates. Neither growth nor Fe(III) reduction by strain AusYE3-1 was observed in anoxic salt-containing medium. The detection of Aplasma group as potential Fe(II) oxidizers and the inhibited Fe(III)-reducing capacity of Acidiphilium contributes to our understanding of the microbial ecology of acidic hypersaline environments.
Denitrification is the main process removing nitrate in river drainage basins and buffer input fr... more Denitrification is the main process removing nitrate in river drainage basins and buffer input from agricultural land and limits aquatic ecosystem pollution. However, the identification of denitrification hotspots (for example, riparian zones), their role in a landscape context and the evolution of their overall removal capacity at the drainage basin scale are still challenging. The main approaches used (that is, mass balance method, denitrification proxies, and potential wetted areas) suffer from methodological drawbacks. We review these approaches and the key frameworks that have been proposed to date to formalize the understanding of the mechanisms driving denitrification: (i) Diffusion versus advection pathways of nitrate transfer, (ii) the biogeochemical hotspot, and (iii) the Damkö hler ratio. Based on these frameworks, we propose to use high-resolution mapping of catchment topography and landscape pattern to define both potential denitrification sites and the dynamic hydrologic modeling at a similar spatial scale (<10 km 2). It would allow the quantification of cumulative denitrification activity at the small catchment scale, using spatially distributed Damkö hler and Peclet numbers and biogeochemical proxies. Integration of existing frameworks with new tools and methods offers the potential for significant breakthroughs in the quantification and modeling of denitrification in small drainage basins. This can provide a basis for improved protection and restoration of surface water and groundwater quality.
The reactivity of natural dissolved organic matter (DOM) towards sulfide and has not been well st... more The reactivity of natural dissolved organic matter (DOM) towards sulfide and has not been well studied with regard to electron transfer, product formation and kinetics. We thus investigated the abiotic transformation of sulfide upon reaction with reduced and non-reduced Sigma Aldrich humic acid (HA), at pH 6 under anoxic conditions. Sulfide reacted with non-reduced HA at conditional rate constants of 0.227~0.325 h(-1). The main transformation products were elemental S (S(0)), and thiosulfate (S2O3(2-)), yielding electron accepting capacities of 2.82~1.75 µmol e(-) (mg C) (-1). Native iron contents in the HA could account for only 6~9% of this electron transfer. About 22~37 % of S reacted with the HA to form organic S (Sorg). For reduced HA, only formation of Sorg was observed and no inorganic transformation products occurred. X-ray absorption near edge structure (XANES) spectroscopy supported Sorg to be mainly about zerovalent, such as thiols, organic di- and polysulfides, or hetero...
Schwertmannite, an iron(III)-oxyhydroxysulfate formed in acidic mining-impacted stream or lake wa... more Schwertmannite, an iron(III)-oxyhydroxysulfate formed in acidic mining-impacted stream or lake waters often contaminated with toxic elements like arsenate or chromate, is able to incorporate high amounts of these oxyanions. Detoxification of the water might be achieved if precipitated arsenated or chromated schwertmannite is fixed in the sediment. However, under reduced conditions, reductive dissolution of iron oxides mediated by the activity of Fe(III)-reducing bacteria might mobilize arsenate and chromate again. In this study, the reduction of synthesized arsenated or chromated schwertmannite by the acidophilic Fe(III)-reducer Acidiphilium cryptum JF-5, isolated from an acidic mining-impacted sediment, was investigated. In TSB medium at pH 2.7 with glucose as electron donor, A. cryptum JF-5 reduced about 10% of the total Fe(III) present in pure synthetic schwertmannite but only 5% of Fe(III) present in arsenated schwertmannite. In contrast to sulfate that was released during the reductive dissolution of pure schwertmannite, arsenate was not released during the reduction of arsenated schwertmannite probably due to the high surface complexation constant of arsenate and Fe(III). In medium containing chromated schwertmannite, no Fe(II) was formed, and no glucose was consumed indicating that chromate might have been toxic to cells of A. cryptum JF-5. Both As(V) or Cr(VI) could not be utilized as electron acceptor by A. cryptum JF-5. A comparison between autoclaved (121 • C for 20 min) and non-autoclaved schwertmannite samples demonstrated that nearly 100% of the bound sulfate was released during heating, and FTIR spectra indicated a transformation of schwertmannite to goethite. This structural change was not observed with autoclaved arsenated or chromated schwertmannite. These results suggest that the mobility of arsenate and chromate is not enhanced by the activity of acidophilic Fe(III)-reducing bacteria in mining-impacted sediments. In contrast, the presence of bound arsenate and chromate seemed to stabilize schwertmannite against reductive dissolution and its further transformation to goethite that is an ongoing process in those sediments.
Liebe Leserinnen und Leser, die Erdgasgewinnung aus unkonventionellen Lagerstätten unter Einsatz ... more Liebe Leserinnen und Leser, die Erdgasgewinnung aus unkonventionellen Lagerstätten unter Einsatz von Hydraulic-Fracturing-Maßnahmen (Fracking) wird derzeit in Deutschland in der Politik, den Medien, der Wissenschaft, der Industrie, den Fach-und Umweltverbänden und den Gewerkschaften intensiv und vielfach emotional diskutiert. Buchstäblich entzündete der Film Gasland diese Diskussion, obwohl der brennende Wasserhahn nachweislich nicht durch Fracking-Maßnahmen verursacht wurde. Auch wenn die Motive der verschiedenen gesellschaftlichen Gruppen unterschiedlich sind, so steht in aller Regel die Sorge um die potenzielle, flächenhafte Kontamination des Grundwassers im Vordergrund dieser Diskussion, d. h. eines der zentralen Themen unserer Fachdisziplin. Der Streit geht insbesondere um die Frage, inwieweit die Grundwasserqualität durch die eingesetzten Fracking
The region of the Nefzawa Oases in the south of the Tunisian Republic is an important region with... more The region of the Nefzawa Oases in the south of the Tunisian Republic is an important region with regards to its production and its tourist value. The System of Oases covers approx. 3000 km² and is limited in the west by the biggest Sahara salt lake, the Chott El Djerid, and in the south by the Sahara desert. Until the beginning of 1970 water had been supplied by artesian wells screened in the deep aquifer systems of the Terminal Complex and the Intercalary Continental. For the last twenty years salination of the Terminal Complex water has been observed locally. Mainly two areas in the Nefzawa Oases are affected by this development towards prohibitively high salinity levels that would prevent this water from being used efficiently in future. One area can be identified in the north of the oases along the Tozeur-Kébili fault, whereas the other one is located to the south of the town of Douz. The hydrogeological situation of the Nefzawa Oases needed testing various hypotheses that exis...
We determined concentrations and diagenetic state of organic matter in two cores from Lake Zug, S... more We determined concentrations and diagenetic state of organic matter in two cores from Lake Zug, Switzerland. To obtain a general picture of organic matter decay in the lake, we measured bulk parameters such as total organic carbon, total nitrogen, and total hydrolyzable amino acids. In addition, we studied specific compound classes in detail-namely, amino acids and chlorins. From these data we obtained two recently proposed indicators for organic matter degradation state-the amino acid-based degradation index (DI) and the chlorin index (CI). The two indicators complement each other, with the CI being very sensitive during the initial stages of organic matter decay and the DI recording later stages of decay. Further differences are likely caused by nonlinear behavior during degradation. Nonetheless, the two proxies agree in the general picture of the degradation state. Despite higher concentrations of organic matter in the surface sediment at the deeper site, neither of the degradation state indicators showed much difference between the two sites. At depth, the degradation state at the two sites diverges, despite similar concentrations of organic matter. Although we cannot explain all differences between bulk parameters, amino acid composition, and chlorins conclusively, the results indicate a combined effect of different organic matter inputs (e.g., through sediment focusing) and different oxygen availability at the two sites since the onset of eutrophication.
Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) m... more Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) may pose a serious threat to groundwater quality. The objective of this study was to characterise the spatial variability of As and Cr concentrations in the solid phase and in the soil water at a former wood impregnation plant and to reveal the fundamental transport processes. The soil was sampled down to a depth of 2m. The soil water was extracted in situ from the vadose zone over a period of 10 months at depths of 1 and 1.5m, using large horizontally installed suction tubes. Groundwater was sampled from a depth of 4.5m. Results showed that arsenic and chromium had accumulated in the upper region of the profile and exhibited a high spatial variability (As: 21-621 mg kg(-1); Cr: 74-2872 mg kg(-1)). Concentrations in the soil water were high (mean As 167 microg L(-1); Cr: 62 microg L(-1)) and also showed a distinct spatial variability, covering concentration ranges up to three orders of magnitude. The variability was caused by the severe water-repellency of the surface soil, induced by the concurrent application of creosote wood preservatives, which leads to strong preferential flow as evident from a dye experiment. In contrast to soil water concentrations, only low As concentrations (&amp;amp;amp;amp;amp;amp;lt;12 microg L(-1)) were detected in the groundwater. High Cr concentrations in the groundwater (approx. 300 microg L(-1)), however, illustrated the pronounced mobility of chromium. Our study shows that at sites with a heterogeneous flow system in the vadose zone a disparity between flux-averaged and volume-averaged concentrations may occur, and sampling of soil water might not be adequate for assessing groundwater concentrations. In these cases long-term monitoring of the groundwater appears to be the best strategy for a groundwater risk assessment.
Assessing the potential for transfer of pollutants and nutrients across catchments is of primary ... more Assessing the potential for transfer of pollutants and nutrients across catchments is of primary importance under changing land use and climate. Over the past decade the connectivity/disconnectivity dynamic of a catchment has been related to its potential to export material; however, we continue to use multiple definitions of connectivity, and most have focused strongly on physical (hydrological or hydraulic) connectivity. In contrast, this paper constantly focuses on the dynamic balance between transport and material transformation, and defines material connectivity as the effective transfer of material between elements of the hydrological cycle. The concept of exposure timescales is developed and used to define three distinct regimes: (i) which is hydrologically connected and transport is dominated by advection; (ii) which is hydrologically connected and transport is dominated by diffusion; and (iii) which is materially isolated. The ratio of exposure timescales to material processing timescales is presented as the non-dimensional number, N E , where N E is reaction-specific and allows estimation of relevant spatial scales over which the reactions of interest take place. Case studies within each regime provide examples of how N E can be used to characterise systems according to their sensitivity to shifts in hydrology and gain insight into the biogeochemical processes that are signficant under the specified conditions. Finally, we explore the implications of the N E framework for improved water management, and for our understanding of biodiversity, resilience and chemical competitiveness under specified conditions.
Goethite (gt), 2-line (2lfh), 6-line ferrihydrite (6lfh), and schwertmannite (shm) were reacted w... more Goethite (gt), 2-line (2lfh), 6-line ferrihydrite (6lfh), and schwertmannite (shm) were reacted with H 2 S under steadystate conditions at pH 2.5-5 using a novel setup that consisted of an electrochemical sulfide generator transporting H 2 S into a suspension of oxides in a fluidized bedreactor. The reactants were stoichiometrically converted into Fe 2+ and S°. Sulfate significantly inhibited the rates. Surface area normalized rates increased with pH. They depended on the mineral type following the order gt > 2lfh > 6lfh, contrasting previous observations at circumneutral pH with an inverse order. The rate of shm dissolution was highest probably due to direct reduction of dissolved ferric iron by H 2 S. A linear relationship between the observed rate and the surface species of H 2 S was derived from a surface complexation approach that allowed for the estimation of intrinsic rate constants k intr for the various oxides (38 min-1 , 1.4 min-1 , 0.29 min-1 for gt, 2lfh, and 6lfh, respectively). k int decreased with increasing ∆G f for the reactions and seems to depend on the reduction potential of the solution. From this observation we derived the hypothesis that k int is determined by the flat-band potential of the mineral/solute interface at low pH while being affected by surface interactions at higher pH.
High As(III) enrichment in schwertmannite precipitated acid mine impacted areas is a major concer... more High As(III) enrichment in schwertmannite precipitated acid mine impacted areas is a major concern considering its acute toxicity and mobility where the current knowledge of their interaction, redox conditions and schwertmannite metastability is inadequate. In this study we have investigated such aspects through batch isotherm, microscopic and spectroscopic techniques. Schwertmannite produced by biotic process with 14.7 m(2)g(-1) surface area demonstrated a rapid As(III) uptake followed by slow retention possibly into the internal absorbing sites through multilayer and heterogeneous sorption processes. Chemical, X-ray diffraction, infrared and microscopic examinations revealed that ionic exchange between schwertmannite SO(4)(2-) and As(III) and surface precipitation governed the total As(III) uptake where lower dissolved SO(4)(2-) and high sorbent mass enhanced As(III) retention. Redox instability of sorbed As(III) was evidenced from the near-edge spectroscopic analysis at extremely high Fe(III):As(III) ratio (5.5×10(5)) leading to surface oxidation to As(V), while As(III) was found as the predominant redox species at high As(III):Fe(III) ratios. Only 0.83% of sorbed As(III) was released which was subsequently re-adsorbed into schwertmannite during 4 months stabilization without any evidence of mineralogical transformation.
The main goal of this study is to analyze import, transfer, fate of PPCPs as trace pollutants in ... more The main goal of this study is to analyze import, transfer, fate of PPCPs as trace pollutants in situ and ex situ. This study attempts to examine the fate and transport of PPCPs in small fields using LC-ESI-MS/MS as a tool to monitor. In addition, transport and sorption of selected PPCPs in undisturbed soil columns will be evaluated with bromide tracer and HYDRUS software. Contribution of preferential flow and colloid-facilitated transport to the overall PPCPs movement to subsurface drain will also be featured in field studies and column experiments in this project. The output of this project will extend our knowledge of PPCPs and other emerging pollutants which are likely to affect organisms as well as human beings. Keyword: pharmaceuticals and personal care products (PPCPs), transport, monitoring, HYDRUS, LC-ESI-MS/MS, preferential flow, colloid-facilitated transport
From 1982 to 2001 acidic conditions prevailed at former lignite mining Lake Knappensee. Since 200... more From 1982 to 2001 acidic conditions prevailed at former lignite mining Lake Knappensee. Since 2001 the acidity of the lake water continuously decreased reaching circum-neutral pH conditions in 2010. Based on acidity time series of the lake water in combination with water budgets derived from a regional groundwater model the cumulative acidity loss in the lake for the time span from 2001 to 2015 can be estimated to be 8400 kmol. Internal neutralization by biogenic sulfate reduction with consecutive deposition of reduced sulfur in the lake sediment was supposed to be the crucial process leading to the observed decrease in lake water acidity. In order to test this hypothesis elaborate quantitative field and laboratory investigations were launched in December 2014. 15 sediment cores distributed over the lake`s area were sampled and analyzed for reduced sulfur species at the hydrological laboratory of the University of Bayreuth. The measured sulfur contents were converted into deposited ...
The Fe(II) monosulfide mineral mackinawite (FeS) is an important phase in low-temperature iron an... more The Fe(II) monosulfide mineral mackinawite (FeS) is an important phase in low-temperature iron and sulfur cycles, yet it is challenging to characterize since it often occurs in X-ray amorphous or nanoparticulate forms and is extremely sensitive to oxidation. Moreover, the electronic configuration of iron in mackinawite is still under debate. Mössbauer spectroscopy has the potential to distinguish mackinawite from other FeS phases and provide clarity on the electronic configuration, but conflicting results have been reported. We therefore conducted a Mössbauer study at 5 K of five samples of mackinawite synthesized through different pathways. Samples show two different Mössbauer patterns: a singlet that remains unsplit at all temperatures studied, and a sextet with a hyperfine magnetic field of 27(1) T at 5 K, or both. Our results suggest that the singlet corresponds to stoichiometric mackinawite (FeS), while the sextet corresponds to mackinawite with excess S (FeS1+x). Both phases s...
Agricultural non-point source (NPS) pollution is a major concern for water quality management in ... more Agricultural non-point source (NPS) pollution is a major concern for water quality management in the Soyang watershed in South Korea. Nutrients (phosphorus and nitrogen), organic matter, and sediment exports in streams were estimated in an agricultural catchment (Haean catchment) for two years. The stream water samples were taken in dry and rainy seasons to evaluate the effect of monsoonal rainfall on pollutants exports. The influence of land use changes on NPS pollution was assessed by conducting a land use census and comparing the NPS characteristic exports. Total phosphorus (TP), suspended solids (SS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) increased dramatically in rainy seasons. Land uses were changed during the study period. Dry fields and rice paddies have decreased distinctively while orchard (apple, grape, and peach) and ginseng crops showed an increase within the catchment. The TP and SS loading decreased in the streams in 2010 compared to the loading in 2009 while the BOD and NO 3 − did not show distinct significant change. In this study, monsoonal driven rainfalls increased exports of agricultural NPS pollutants into streams. Land use change (mostly crop and paddy fields to orchards and ginseng fields) remarkably mitigated TP and SS exports into the streams.
We investigated the microbial community compositions in two sediment samples from the acidic (pH ... more We investigated the microbial community compositions in two sediment samples from the acidic (pH ∼3) and hypersaline (>4.5% NaCl) surface waters, which are widespread in Western Australia. In West Dalyup River, large amounts of NaCl, Fe(II) and sulfate are brought by the groundwater into the surface runoff. The presence of K-jarosite and schwertmannite minerals in the river sediments suggested the occurrence of microbial Fe(II) oxidation because chemical oxidation is greatly reduced at low pH. 16S rRNA gene diversity analyses revealed that sequences affiliated with an uncultured archaeal lineage named Aplasma, which has the genomic potential for Fe(II) oxidation, were dominant in both sediment samples. The acidophilic heterotrophs Acidiphilium and Acidocella were identified as the dominant bacterial groups. Acidiphilium strain AusYE3-1 obtained from the river sediment tolerated up to 6% NaCl at pH 3 under oxic conditions and cells of strain AusYE3-1 reduced the effects of high salt content by forming filamentous structure clumping as aggregates. Neither growth nor Fe(III) reduction by strain AusYE3-1 was observed in anoxic salt-containing medium. The detection of Aplasma group as potential Fe(II) oxidizers and the inhibited Fe(III)-reducing capacity of Acidiphilium contributes to our understanding of the microbial ecology of acidic hypersaline environments.
Denitrification is the main process removing nitrate in river drainage basins and buffer input fr... more Denitrification is the main process removing nitrate in river drainage basins and buffer input from agricultural land and limits aquatic ecosystem pollution. However, the identification of denitrification hotspots (for example, riparian zones), their role in a landscape context and the evolution of their overall removal capacity at the drainage basin scale are still challenging. The main approaches used (that is, mass balance method, denitrification proxies, and potential wetted areas) suffer from methodological drawbacks. We review these approaches and the key frameworks that have been proposed to date to formalize the understanding of the mechanisms driving denitrification: (i) Diffusion versus advection pathways of nitrate transfer, (ii) the biogeochemical hotspot, and (iii) the Damkö hler ratio. Based on these frameworks, we propose to use high-resolution mapping of catchment topography and landscape pattern to define both potential denitrification sites and the dynamic hydrologic modeling at a similar spatial scale (<10 km 2). It would allow the quantification of cumulative denitrification activity at the small catchment scale, using spatially distributed Damkö hler and Peclet numbers and biogeochemical proxies. Integration of existing frameworks with new tools and methods offers the potential for significant breakthroughs in the quantification and modeling of denitrification in small drainage basins. This can provide a basis for improved protection and restoration of surface water and groundwater quality.
The reactivity of natural dissolved organic matter (DOM) towards sulfide and has not been well st... more The reactivity of natural dissolved organic matter (DOM) towards sulfide and has not been well studied with regard to electron transfer, product formation and kinetics. We thus investigated the abiotic transformation of sulfide upon reaction with reduced and non-reduced Sigma Aldrich humic acid (HA), at pH 6 under anoxic conditions. Sulfide reacted with non-reduced HA at conditional rate constants of 0.227~0.325 h(-1). The main transformation products were elemental S (S(0)), and thiosulfate (S2O3(2-)), yielding electron accepting capacities of 2.82~1.75 µmol e(-) (mg C) (-1). Native iron contents in the HA could account for only 6~9% of this electron transfer. About 22~37 % of S reacted with the HA to form organic S (Sorg). For reduced HA, only formation of Sorg was observed and no inorganic transformation products occurred. X-ray absorption near edge structure (XANES) spectroscopy supported Sorg to be mainly about zerovalent, such as thiols, organic di- and polysulfides, or hetero...
Schwertmannite, an iron(III)-oxyhydroxysulfate formed in acidic mining-impacted stream or lake wa... more Schwertmannite, an iron(III)-oxyhydroxysulfate formed in acidic mining-impacted stream or lake waters often contaminated with toxic elements like arsenate or chromate, is able to incorporate high amounts of these oxyanions. Detoxification of the water might be achieved if precipitated arsenated or chromated schwertmannite is fixed in the sediment. However, under reduced conditions, reductive dissolution of iron oxides mediated by the activity of Fe(III)-reducing bacteria might mobilize arsenate and chromate again. In this study, the reduction of synthesized arsenated or chromated schwertmannite by the acidophilic Fe(III)-reducer Acidiphilium cryptum JF-5, isolated from an acidic mining-impacted sediment, was investigated. In TSB medium at pH 2.7 with glucose as electron donor, A. cryptum JF-5 reduced about 10% of the total Fe(III) present in pure synthetic schwertmannite but only 5% of Fe(III) present in arsenated schwertmannite. In contrast to sulfate that was released during the reductive dissolution of pure schwertmannite, arsenate was not released during the reduction of arsenated schwertmannite probably due to the high surface complexation constant of arsenate and Fe(III). In medium containing chromated schwertmannite, no Fe(II) was formed, and no glucose was consumed indicating that chromate might have been toxic to cells of A. cryptum JF-5. Both As(V) or Cr(VI) could not be utilized as electron acceptor by A. cryptum JF-5. A comparison between autoclaved (121 • C for 20 min) and non-autoclaved schwertmannite samples demonstrated that nearly 100% of the bound sulfate was released during heating, and FTIR spectra indicated a transformation of schwertmannite to goethite. This structural change was not observed with autoclaved arsenated or chromated schwertmannite. These results suggest that the mobility of arsenate and chromate is not enhanced by the activity of acidophilic Fe(III)-reducing bacteria in mining-impacted sediments. In contrast, the presence of bound arsenate and chromate seemed to stabilize schwertmannite against reductive dissolution and its further transformation to goethite that is an ongoing process in those sediments.
Liebe Leserinnen und Leser, die Erdgasgewinnung aus unkonventionellen Lagerstätten unter Einsatz ... more Liebe Leserinnen und Leser, die Erdgasgewinnung aus unkonventionellen Lagerstätten unter Einsatz von Hydraulic-Fracturing-Maßnahmen (Fracking) wird derzeit in Deutschland in der Politik, den Medien, der Wissenschaft, der Industrie, den Fach-und Umweltverbänden und den Gewerkschaften intensiv und vielfach emotional diskutiert. Buchstäblich entzündete der Film Gasland diese Diskussion, obwohl der brennende Wasserhahn nachweislich nicht durch Fracking-Maßnahmen verursacht wurde. Auch wenn die Motive der verschiedenen gesellschaftlichen Gruppen unterschiedlich sind, so steht in aller Regel die Sorge um die potenzielle, flächenhafte Kontamination des Grundwassers im Vordergrund dieser Diskussion, d. h. eines der zentralen Themen unserer Fachdisziplin. Der Streit geht insbesondere um die Frage, inwieweit die Grundwasserqualität durch die eingesetzten Fracking
The region of the Nefzawa Oases in the south of the Tunisian Republic is an important region with... more The region of the Nefzawa Oases in the south of the Tunisian Republic is an important region with regards to its production and its tourist value. The System of Oases covers approx. 3000 km² and is limited in the west by the biggest Sahara salt lake, the Chott El Djerid, and in the south by the Sahara desert. Until the beginning of 1970 water had been supplied by artesian wells screened in the deep aquifer systems of the Terminal Complex and the Intercalary Continental. For the last twenty years salination of the Terminal Complex water has been observed locally. Mainly two areas in the Nefzawa Oases are affected by this development towards prohibitively high salinity levels that would prevent this water from being used efficiently in future. One area can be identified in the north of the oases along the Tozeur-Kébili fault, whereas the other one is located to the south of the town of Douz. The hydrogeological situation of the Nefzawa Oases needed testing various hypotheses that exis...
We determined concentrations and diagenetic state of organic matter in two cores from Lake Zug, S... more We determined concentrations and diagenetic state of organic matter in two cores from Lake Zug, Switzerland. To obtain a general picture of organic matter decay in the lake, we measured bulk parameters such as total organic carbon, total nitrogen, and total hydrolyzable amino acids. In addition, we studied specific compound classes in detail-namely, amino acids and chlorins. From these data we obtained two recently proposed indicators for organic matter degradation state-the amino acid-based degradation index (DI) and the chlorin index (CI). The two indicators complement each other, with the CI being very sensitive during the initial stages of organic matter decay and the DI recording later stages of decay. Further differences are likely caused by nonlinear behavior during degradation. Nonetheless, the two proxies agree in the general picture of the degradation state. Despite higher concentrations of organic matter in the surface sediment at the deeper site, neither of the degradation state indicators showed much difference between the two sites. At depth, the degradation state at the two sites diverges, despite similar concentrations of organic matter. Although we cannot explain all differences between bulk parameters, amino acid composition, and chlorins conclusively, the results indicate a combined effect of different organic matter inputs (e.g., through sediment focusing) and different oxygen availability at the two sites since the onset of eutrophication.
Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) m... more Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) may pose a serious threat to groundwater quality. The objective of this study was to characterise the spatial variability of As and Cr concentrations in the solid phase and in the soil water at a former wood impregnation plant and to reveal the fundamental transport processes. The soil was sampled down to a depth of 2m. The soil water was extracted in situ from the vadose zone over a period of 10 months at depths of 1 and 1.5m, using large horizontally installed suction tubes. Groundwater was sampled from a depth of 4.5m. Results showed that arsenic and chromium had accumulated in the upper region of the profile and exhibited a high spatial variability (As: 21-621 mg kg(-1); Cr: 74-2872 mg kg(-1)). Concentrations in the soil water were high (mean As 167 microg L(-1); Cr: 62 microg L(-1)) and also showed a distinct spatial variability, covering concentration ranges up to three orders of magnitude. The variability was caused by the severe water-repellency of the surface soil, induced by the concurrent application of creosote wood preservatives, which leads to strong preferential flow as evident from a dye experiment. In contrast to soil water concentrations, only low As concentrations (&amp;amp;amp;amp;amp;amp;lt;12 microg L(-1)) were detected in the groundwater. High Cr concentrations in the groundwater (approx. 300 microg L(-1)), however, illustrated the pronounced mobility of chromium. Our study shows that at sites with a heterogeneous flow system in the vadose zone a disparity between flux-averaged and volume-averaged concentrations may occur, and sampling of soil water might not be adequate for assessing groundwater concentrations. In these cases long-term monitoring of the groundwater appears to be the best strategy for a groundwater risk assessment.
Assessing the potential for transfer of pollutants and nutrients across catchments is of primary ... more Assessing the potential for transfer of pollutants and nutrients across catchments is of primary importance under changing land use and climate. Over the past decade the connectivity/disconnectivity dynamic of a catchment has been related to its potential to export material; however, we continue to use multiple definitions of connectivity, and most have focused strongly on physical (hydrological or hydraulic) connectivity. In contrast, this paper constantly focuses on the dynamic balance between transport and material transformation, and defines material connectivity as the effective transfer of material between elements of the hydrological cycle. The concept of exposure timescales is developed and used to define three distinct regimes: (i) which is hydrologically connected and transport is dominated by advection; (ii) which is hydrologically connected and transport is dominated by diffusion; and (iii) which is materially isolated. The ratio of exposure timescales to material processing timescales is presented as the non-dimensional number, N E , where N E is reaction-specific and allows estimation of relevant spatial scales over which the reactions of interest take place. Case studies within each regime provide examples of how N E can be used to characterise systems according to their sensitivity to shifts in hydrology and gain insight into the biogeochemical processes that are signficant under the specified conditions. Finally, we explore the implications of the N E framework for improved water management, and for our understanding of biodiversity, resilience and chemical competitiveness under specified conditions.
Goethite (gt), 2-line (2lfh), 6-line ferrihydrite (6lfh), and schwertmannite (shm) were reacted w... more Goethite (gt), 2-line (2lfh), 6-line ferrihydrite (6lfh), and schwertmannite (shm) were reacted with H 2 S under steadystate conditions at pH 2.5-5 using a novel setup that consisted of an electrochemical sulfide generator transporting H 2 S into a suspension of oxides in a fluidized bedreactor. The reactants were stoichiometrically converted into Fe 2+ and S°. Sulfate significantly inhibited the rates. Surface area normalized rates increased with pH. They depended on the mineral type following the order gt > 2lfh > 6lfh, contrasting previous observations at circumneutral pH with an inverse order. The rate of shm dissolution was highest probably due to direct reduction of dissolved ferric iron by H 2 S. A linear relationship between the observed rate and the surface species of H 2 S was derived from a surface complexation approach that allowed for the estimation of intrinsic rate constants k intr for the various oxides (38 min-1 , 1.4 min-1 , 0.29 min-1 for gt, 2lfh, and 6lfh, respectively). k int decreased with increasing ∆G f for the reactions and seems to depend on the reduction potential of the solution. From this observation we derived the hypothesis that k int is determined by the flat-band potential of the mineral/solute interface at low pH while being affected by surface interactions at higher pH.
High As(III) enrichment in schwertmannite precipitated acid mine impacted areas is a major concer... more High As(III) enrichment in schwertmannite precipitated acid mine impacted areas is a major concern considering its acute toxicity and mobility where the current knowledge of their interaction, redox conditions and schwertmannite metastability is inadequate. In this study we have investigated such aspects through batch isotherm, microscopic and spectroscopic techniques. Schwertmannite produced by biotic process with 14.7 m(2)g(-1) surface area demonstrated a rapid As(III) uptake followed by slow retention possibly into the internal absorbing sites through multilayer and heterogeneous sorption processes. Chemical, X-ray diffraction, infrared and microscopic examinations revealed that ionic exchange between schwertmannite SO(4)(2-) and As(III) and surface precipitation governed the total As(III) uptake where lower dissolved SO(4)(2-) and high sorbent mass enhanced As(III) retention. Redox instability of sorbed As(III) was evidenced from the near-edge spectroscopic analysis at extremely high Fe(III):As(III) ratio (5.5×10(5)) leading to surface oxidation to As(V), while As(III) was found as the predominant redox species at high As(III):Fe(III) ratios. Only 0.83% of sorbed As(III) was released which was subsequently re-adsorbed into schwertmannite during 4 months stabilization without any evidence of mineralogical transformation.
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Papers by Stefan Peiffer