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  • 1
    Language: German
    In: Grundwasser, 2017, Vol.22(1), pp.1-1
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s00767-016-0351-y Byline: Stefan Peiffer (1) Author Affiliation: (1) Universitat Bayreuth, Bayreuth, Deutschland Article History: Registration Date: 30/12/2016 Received Date: 01/12/2016 Accepted Date: 30/12/2016 Online Date: 26/01/2017
    Keywords: Environmental Sciences ; Geography;
    ISSN: 1430-483X
    E-ISSN: 1432-1165
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  • 2
    Language: English
    In: Chemosphere, 2012, Vol.86(6), pp.557-564
    Description: ► As(III) retention is very rapid. ► High Fe(III)/As(III) ratio can cause oxidation of sorbed As(III). ► Total As(III) uptake is controlled by ligand exchange and possible surface precipitates. ► Sorbed As(III) binds strongly releasing negligible fractions upon re-suspension. ► Retained As(III) restricts mineralogical transformation. 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 g 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 and As(III) and surface precipitation governed the total As(III) uptake where lower dissolved 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 ) 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.
    Keywords: Acid Mine Drainage ; As(III) Oxidation ; Arsenite Sorption ; Surface Precipitation ; Ligand Exchange ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 3
    Language: English
    In: Applied Geochemistry, October 2016, Vol.73, pp.8-12
    Description: Sulphate reduction is a key reaction to remove acidity from water bodies affected by acid mine drainage. In this study, S SO reduction rates determined in sediments from a variety of acidic lignite pit lakes have been compiled. The rates decreased with pH and are strongly dependent on carbon substrate. The rates were fitted to a Monod model adapted to the specific conditions of acidic pit lakes (APL) sediments: i) sulphate reduction rate is independent from sulphate concentration due to the high concentration typically observed in APL systems (10–30 mM), ii) the observed pH dependency of sulphate reduction was accounted for by an inhibition function F which considers the occurrence of low cell numbers of sulphate reducing bacteria at pH values 〈 4.75. Simulated steady-state sulphate reduction rates are predicting measured rates at carbon substrate concentrations of 〈10 μM. Estimated steady-state reaction time scales range between 2.4 h at pH 7 and 41 h at pH 3 at a carbon half-saturation constant of K  = 100 μM and are increasing with increasing K values. Time scales at low pH are too long to allow for significant generation of alkalinity during the time of residence of groundwater passing through the top and hence most reactive zone of APL sediments which has important implications for the remediation of acidic pit lakes.
    Keywords: Sulphate Reduction Rates ; Acid Pit Lakes ; Monod Kinetics ; Modelling ; Acidity ; Internal Neutralisation ; Residence Time ; Sediments ; Geology
    ISSN: 0883-2927
    E-ISSN: 1872-9134
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  • 4
    Language: English
    In: Journal of Hydrology, August 2018, Vol.563, pp.260-272
    Description: Riparian wetlands as both hydrological and biogeochemical hot spots often have a major impact on the release of solutes from headwater catchments. Numerous studies give some evidence of a rather complex interplay of hydrological and biogeochemical processes that is still poorly understood. This study seeks to address this challenge using a multivariate solute concentration data set from a small riparian headwater wetland. First, a non-linear variant of the Principal Component Analysis (Isomap) was performed in a preceding study to identify prevailing biogeochemical processes controlling water chemistry. Second, the scores of the components of the stream draining the wetland were subjected to a cluster analysis to identify typical biogeochemical patterns for different biogeochemical and hydrological boundary conditions. Four different clusters could be identified, which roughly followed a seasonal pattern, although modified by hydrological boundary conditions in the short-term. During the first three months of the year, Cluster 3 prevailed, indicating a discharge of rather unaltered shallow to mean depth groundwater. Cluster 3 was increasingly replaced by Cluster 2 and then subsequently by Cluster 1, indicating increasingly anoxic conditions, increasing denitrification and desulphurization, and increasing decomposition of organic carbon reflecting increasing biological activity and increasing water residence time within the wetland. However, stream water during stormflow after extended periods of low groundwater level in the second half of the growth season exhibited a very distinct pattern, represented by the fourth cluster. It indicated strong oxic conditions causing enhanced oxidation of sulphides, a corresponding decrease in pH values, and a substantial increase in the concentration of alkaline earth ions, manganese and in electric conductivity during the dry period. It is concluded that temporal variations in stream water chemistry clearly reflected the intensity of biological activity in the wetland, interacting with water table dynamics. Our results provide strong evidence for major effects of single extreme events like drought periods which are expected to become more frequent because of climate change.
    Keywords: Stream Water Chemistry ; Solute Export ; Riparian Wetland ; Biogeochemistry ; Seasonality ; Cluster Analysis ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 5
    Language: English
    In: Journal of Hazardous Materials, Jan 30, 2014, Vol.265, p.208(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhazmat.2013.11.068 Byline: Susanta Paikaray, Joseph Essilfie-Dughan, Jorg Gottlicher, Kilian Pollok, Stefan Peiffer Abstract: acents Schwertmannite is a better scavenger than goethite in identical sorbent:solute ratio. acents Partial As(III) oxidation to As(V) by schwertmannite and goethite in anoxic media. acents Arsenic-rich surface precipitates form on schwertmannite with decayed morphology. acents Bidentate binuclear binding of both As(V) and mixed As(III)-As(V) on schwertmannite. acents Dissolved ferrous iron has negligible control on As(III) uptake and redox stability. Author Affiliation: (a) Department of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany (b) Department of Geological Sciences, University of Saskatchewan, SK S7N 5E2, Canada (c) Institute for Synchrotron Radiation, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany (d) Institute of Geosciences, Friedrich Schiller University of Jena, Carl-Zeiss-Promenade 10, 07745 Jena, Germany (e) Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Bhopal, Madhya Pradesh 462023, India Article History: Received 1 July 2013; Revised 26 November 2013; Accepted 30 November 2013
    Keywords: Nuclear Radiation ; Iron Oxides ; Hydrology ; Iron Compounds ; Arsenic
    ISSN: 0304-3894
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Journal of Hydrology, Feb 13, 2014, Vol.509, p.601(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2013.12.005 Byline: Svenja Bartsch, Sven Frei, Marianne Ruidisch, Christopher L. Shope, Stefan Peiffer, Bomchul Kim, Jan H. Fleckenstein Abstract: acents Temporal variability of river-aquifer exchange fluxes is controlled by the monsoon. acents Monsoonal extreme precipitation events are dominant drivers for flow reversals. acents Frequent flow reversals affect the local water quality. Article History: Received 26 August 2013; Revised 3 December 2013; Accepted 5 December 2013 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of Philippe Negrel, Associate Editor
    Keywords: Aquifers ; Rain ; Climate
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Geochimica et Cosmochimica Acta, 15 November 2017, Vol.217, pp.334-348
    Description: The formation of pyrite has been extensively studied because of its abundance in many anoxic environments. Yet, there is no consensus on the underlying pathways and kinetics of its formation. We studied the formation of pyrite during the reaction between reactive ferric hydroxides (goethite and lepidocrocite) and aqueous sulfide in an anoxic glove box at neutral pH. The formation of pyrite was monitored with Mössbauer spectroscopy using Fe isotope-enriched ferric (hydr)oxides. The initial molar ratios of Fe(III):S(-II) were adjusted to be ‘high’ with Fe(III) concentrations in excess of sulfide (HR) and ‘low’ (LR) with excess of sulfide. Approximately the same surface area was applied in all HR runs in order to compare the mineral reactivity of ferric hydroxides. Electron transfer between aqueous sulfide and ferric hydroxides in the first 2 h led to the formation of ferrous iron and methanol-extractable oxidized sulfur (MES). Metastable FeS formed in all of the experiments. Pyrite formed at a different rate in HR and LR runs although the MES and ferrous iron concentrations were rather similar. In all HR runs, pyrite formation started after 48 h and achieved a maximum concentration after 1 week. In contrast, pyrite started to form only after 2 months in LR runs (Fe(III):S(-II) ∼ 0.2) with goethite and no pyrite formation was observed in LR with lepidocrocite after 6 months. Rates in LR runs were at least 2–3 orders of magnitude slower than in HR runs. Sulfide oxidation rates were higher with lepidocrocite than with goethite, but no influence of the mineral type on pyrite formation rates in HR runs could be observed. Pyrite formation rates in HR runs could not be predicted by the classical model of Rickard (1975). We therefore propose a novel ferric-hydroxide-surface (FHS) pathway for rapid pyrite formation that is based on the formation of a precursor species 〉Fe S . Its formation is competitive to FeS precipitation at high aqueous sulfide concentrations and requires that a fraction of the ferric hydroxide surface not be covered by a surface precipitate of FeS . Hence, pyrite formation rate decreases with decreasing Fe(III):S(-II) ratio. In LR runs, pyrite formation appears to follow the model of Rickard (1975) and to be kinetically controlled by the dissolution of FeS. The FHS-pathway will be prominent in many aquatic systems with terrestrial influence, i.e. abundance of ferric iron. We propose that the Fe(III):S(-II) ratio can be used as an indicator for rapid pyrite formation during early diagenesis in anoxic/suboxic aquatic systems.
    Keywords: Rapid Pyrite Formation ; Pathway ; Polysulfides ; Reactive Ferrous Iron ; Iron-Sulfur Interaction ; Ferric Hydroxides ; Mössbauer Spectroscopy ; Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 8
    Language: English
    In: Geochimica et Cosmochimica Acta, 15 November 2017, Vol.217, pp.292-305
    Description: Schwertmannite (SHM) is a powerful scavenger for As(III) leading to As(III)-enriched precipitates around acid mine drainage environments that may become exposed to aqueous Fe(II). In this study we have investigated the stability of pure SHM and SHM containing 0.92 wt% As(III) under Fe(II) -rich (0.4–1.0 mM) anoxic conditions using XRD, SEM, Mössbauer and FTIR spectroscopic techniques. Schwertmannite transformation proceeded through an alkalinity-driven pathway releasing sulfate and a Fe(II)-catalyzed pathway that generated lepidocrocite and goethite at pH 6 and 6.9 in the presence of 1 mM Fe(II) . Lepidocrocite was found to be needle shaped if the SHM contained As(III) and platy for pure SHM. Goethite had a poor degree of crystallinity in As(III) containing SHM. Pre-adsorption of As(III) inhibited the extent of SHM transformation. Fe(II) sorption onto SHM was pH dependent and reflected a sorption edge with complete consumption at pH 6.9, while only ∼20% were adsorbed at pH 5. Surface coverage with Fe(II) appears to be the key parameter controlling extent and products of the transformation process. As(III) concentrations in solution are controlled by two mechanisms: (1) exchange of As(III) for sulfate upon alkalinity-driven transformation of schwertmannite and (2) re-adsorption to new phases formed upon Fe(II)-catalyzed transformation. The adsorbed As(III) has inhibited the extent of transformation and was partly released with the maximum release at pH 5 (0.5%) in the absence of Fe(II) .
    Keywords: Schwertmannite ; Acid Mine Drainage ; Lepidocrocite ; Goethite ; Arsenic ; Fe(II) Catalyzed Transformation ; Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 9
    Language: German
    In: Grundwasser, 6/2014, Vol.19(2), pp.105-105
    Keywords: Earth Sciences ; Hydrogeology ; Hydrology/Water Resources ; Waste Management/Waste Technology ; Mechanics ; Soil Science & Conservation ; Geoecology/Natural Processes ; Environmental Sciences ; Geography;
    ISSN: 1430-483X
    E-ISSN: 1432-1165
    Source: Springer (via CrossRef)
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  • 10
    Language: English
    In: Journal of Hydrology, Nov 27, 2014, Vol.519, p.1560(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2014.09.005 Byline: Christina Weyer, Stefan Peiffer, Kerstin Schulze, Werner Borken, Gunnar Lischeid Abstract: * A systematic approach is used to identify biogeochemical hot spots in a catchment. * Only three prevailing processes explained 89% of the variance of solute concentration. * Hot spots were identified with respect to these different biogeochemical processes. * Hot spots were found for all 15 solutes along different flow paths. * Up to 97% of the biogeochemical transformation were restricted to 2% of the regolith. Article History: Received 20 May 2014; Revised 24 August 2014; Accepted 3 September 2014 Article Note: (miscellaneous) This manuscript was handled by Corrado Corradini, Editor-in-Chief, with the assistance of Barbara Mahler, Associate Editor
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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