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Applied geochemistry : journal of the Internationa... 20건

  1. [해외논문]   Characterization of selected conservative and non-conservative isotopes in mine effluent and impacted surface waters: Implications for tracer applications at the mine-site scale   SCI SCIE SCOPUS

    Larkins, Clayton (The Geological Survey of Finland, Industrial Environments and Recycling, P.O. Box 1237, FI- 70211, Kuopio, Finland ) , Turunen, Kaisa (The Geological Survey of Finland, Industrial Environments and Recycling, P.O. Box 1237, FI- 70211, Kuopio, Finland ) , Mä (The Geological Survey of Finland, Finnish Geosciences Research Laboratory, Klariksentie 1 B 27, 02250, Espoo, Finland ) , nttä (The Geological Survey of Finland, Finnish Geosciences Research Laboratory, P.O. Box 96, FI- 02151, Espoo, Finland ) , ri, Irmeli (The Geological Survey of Finland, Groundwater Unit, P.O. Box 96, FI- 02151, Espoo, Finland ) , Lahaye, Yann (The Geological Survey of Finland, Industrial Environments and Recycling, P.O. Box 1237, FI- 70211, Kuopio, Finland ) , Hendriksson, Nina (The Geological Survey of Finland, Industrial Environments and Recycling, P.O. Box 1237, FI- 70211, Kuopio, Finland) , Forsman, Pekka , Backnä , s, Soile
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 1 - 13 , 2018 , 0883-2927 ,

    초록

    Abstract Effluent from Europe's largest active gold mine is discharged to the adjacent River Seurujoki via natural treatment wetlands in Lapland Finland. Site waters, including two sources of mine effluent, treatment wetland surface water and Seurujoki river water were chemically and isotopically characterized. The results of isotopic characterization were evaluated to determine the effectiveness of selected environmental conservative isotopes ( δ 18 O, δ D, 87 Sr/ 86 Sr ) as tracers of water/solute source. Non-conservative isotopes ( δ 7 Li, δ 26 Mg, δ 25 Mg, δ 34 S SO4 ) were evaluated as tracers of fractionation inducing processes that provide insight to contaminant attenuation and mobility mechanisms. The two sources of mine effluent were chemically distinct, and the impacts of mine effluent were persistent in downstream river water to at least 12.8 km. Sr isotope-based estimates of mine effluent discharge to the river were in good agreement with Cl concentration-based estimates, and suggest effluent comprised approximately 4% of river discharge in both June 2013 and June 2015. These instantaneous mixing results were applied in a multi-isotope approach to characterize non-conservative solute and isotopic behavior for Li and SO 4 . In 2015 7 Li was enriched in downstream river water by approximately 3‰ with no discernible concentration change, suggesting ongoing in-stream ion exchange reactions with oxy-hydroxide precipitates. While SO 4 was attenuated by over 50% in the downstream direction, the observed 34 S SO4 depletion indicates that bacterial sulfate reduction was not a driver of in-stream attenuation. Further, depletion of 18 O and deuterium in treatment wetland 4 indicated that fresh meteoric water comprised approximately 25% of the treatment wetland discharge in March 2015. The contemporaneous flushing of numerous contaminants (Na, Ca, Mg, SO 4 , Mn, and Li) from the wetland supports the conceptual model in which disruption of contaminant concentration gradients will lead to contaminant leaching from the wetlands. Highlights Active gold mine effluent characterized using chemical and isotopic methods. Mine impacts are evident in downstream river water chemistry for at least 12.8 km. Conservative tracers ( 87 Sr/ 86 Sr and Cl) used to allocate solute sources in river. 7 Li/ 6 Li and 34 S SO4 in mine-impacted waters indicate controls on solute mobility. Fresh water influx to treatment wetland mobilizes Na, Ca, Mg, SO 4 , Mn, and Li.

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  2. [해외논문]   Formation and characterization of ternary (Na, NH4, H3O)-jarosites produced from Acidithiobacillus ferrooxidans cultures   SCI SCIE SCOPUS

    Jones, F. Sandy (School of Environment and Natural Resources, Ohio State University, Columbus, OH 43210, USA ) , Bigham, Jerry M. (School of Environment and Natural Resources, Ohio State University, Columbus, OH 43210, USA ) , Gramp, Jonathan P. (Department of Microbiology, Ohio State University, Columbus, OH 43210, USA ) , Tuovinen, Olli H. (Department of Microbiology, Ohio State University, Columbus, OH 43210, USA)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 14 - 22 , 2018 , 0883-2927 ,

    초록

    Abstract The purpose of this study was to characterize a series of (Na, NH 4 , H 3 O)-jarosites produced with various combinations of NH 4 + + Na + in cultures of Acidithiobacillus ferrooxidans that simulated acid solutions from bioleaching systems. The solution concentrations utilized were 6.1, 80, 160 and 320 mM for NH 4 + and 0, 50, 100, 250 and 500 mM for Na + as their respective sulfates. Media at pH 2.2 were inoculated with iron-oxidizing A. ferrooxidans and incubated in shake flasks at 22 ± 2 °C. As the bacteria oxidized ferrous sulfate, ferric iron hydrolyzed and precipitated as schwertmannite (idealized formula Fe 8 O 8 (OH) 6 (SO 4 ).nH 2 O) and/or as solid solution jarosites [(Na, NH 4 , H 3 O)-Fe 3 (SO 4 ) 2 (OH) 6 )] depending on the relative and absolute concentrations of NH 4 + and Na + . The precipitates were characterized by elemental analysis, X-ray diffraction, specific surface area, and Munsell color. Schwertmannite was the dominant mineral product at low combinations of Na + (≤50 mM) and NH 4 + (≤80 mM) in the media after 2 weeks of aging. At higher single or combined concentrations and with aging for 6 and 11 weeks, the formation of yellowish, solid solution jarosites was enhanced. Precipitation of jarosite-group minerals was favored by NH 4 + relative to Na + . Color (Munsell hue) was a useful tool for assessing sample mineralogy after extended aging, but the presence of abundant, poorly crystalline schwertmannite tended to mask the color of admixed jarosite-group minerals after only 2 weeks of contact with the culture media. The purest samples of jarosite-type minerals had specific surface areas 2 /g. Unit cell edge lengths and cell volume calculations from powder XRD data indicated that the jarositic phases produced were ternary (Na, NH 4 , H 3 O)-solid solutions. Most products also appeared to be deficient in structural Fe, especially at low NH 4 contents. Thus, ferric iron precipitation from the simulated bioleaching systems yielded solid solutions of jarosites with chemical compositions that were dependent on the relative concentrations of Na + and NH 4 + in the synthesis media. No phase separations involving discrete, end-member Na-, NH 4 -, or H 3 O-jarosites were detected. Highlights Ternary (Na, NH 4 , H 3 O) jarosites were precipitated in cultures of A. ferrooxidans . H 3 O substitution for structural Na/NH 4 occurred in all samples. Crystallization of jarosites was enhanced by NH 4 + relative to Na + and by aging. Schwertmannite was formed at low NH 4 + (≤80 mM) and all Na + concentrations. Graphical abstract [DISPLAY OMISSION]

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  3. [해외논문]   Nitrate sources, accumulation and reduction in groundwater from Northern Italy: Insights provided by a nitrate and boron isotopic database   SCI SCIE SCOPUS

    Martinelli, G. (ARPAE Environmental Protection Agency, Emilia Romagna Region, Reggio Emilia, Italy ) , Dadomo, A. (Geoinvest Srl, Piacenza, Italy ) , De Luca, D.A. (Department of Earth Sciences, University of Torino, Italy ) , Mazzola, M. (ARPAV Environmental Protection Agency, Veneto Region, Vicenza, Italy ) , Lasagna, M. (Department of Earth Sciences, University of Torino, Italy ) , Pennisi, M. (Institute of Geosciences and Earth Resources (IGG), CNR, Pisa, Italy ) , Pilla, G. (Department of Earth and Environmental Sciences, University of Pavia, Italy ) , Sacchi, E. (Department of Earth and Environmental Sciences, University of Pavia, Italy ) , Saccon, P. (Waterdrop Consulting, Graz, Austria)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 23 - 35 , 2018 , 0883-2927 ,

    초록

    Abstract Large volumes of precious water resources are negatively affected by nitrate contamination, and the problem of the world population's exposure to this is becoming an even more pressing issue. To tackle this problem, the application of environmental isotopes has proven to be an effective method to identify the N origins and major transformations in different environments. In this work, nitrate (δ 15 N NO3 and δ 18 O NO3 ) and boron (δ 11 B) isotope analyses performed in the last twenty years in groundwater from shallow aquifers of the Po plain area, a complex hydrogeological system of European relevance, have been compiled in a comprehensive database together with major ionic contents; these data were integrated with additional original results, targeting areas not previously examined or complementing the available information. Such data, previously interpreted on the local scale, are examined at the Po plain scale, providing an understanding of the N sources and dynamics in the shallow aquifers, and defining the most important processes governing nitrate contamination in Northern Italy. The most impacted groundwater is that hosted in the alluvial fans of the Alpine and Apennine foothills, due to a combination of high soil permeability and presence of intensive agricultural activities. Here, aquifers are characterized by fast circulation and by great water table depths. On the contrary, nitrate contamination is absent in most low plain areas, with shallow water table depths but lower soil permeability, due to the presence of denitrification processes. The δ 15 N median values, calculated for each province, are significantly correlated with pig density. Hence, manure represents one of the main nitrate sources in groundwater from agriculture, the other being synthetic fertilizers. Isotopic compositions enriched due to denitrification are present in ∼22% of the data, being responsible for nitrate abatement in groundwater affecting up to 70–80% of the original content. The B systematics, in such a low geogenic-B context, proved the presence in the investigated area of another anthropogenic nitrate source of civil origin (i.e. sewage). While new results on the local B sources are reported, the garnering of all groundwater data allowed us to define the range of the expected geogenic B signature (δ 11 B = +13 ± 2.5‰). This contribution is a significant step forward for the use of the coupled δ 15 N - δ 11 B toolbox in the study area, previously limited by a poor definition of the compositional end-members. This georeferenced set of hydrochemical and isotopic data will lay the foundations for future monitoring activities and advanced data treatment or modelling. In addition, since the hydrogeological setting of the investigated area shows common features to alluvial basins located near mountain ranges, the approach and the results presented in this study serve as a reference for other study areas worldwide. Highlights 648 δ 15 N NO3 , 403 δ 18 O NO3 and 27 δ 11 B georeferenced groundwater data discussed. δ 15 N median values are significantly correlated at the basin scale with pig density. Nitrates are absent in most low plain areas due to denitrification. δ 11 B data proved the presence of a contamination by sewage. The expected geogenic δ 11 B in the Po plain is +13 ± 2.5‰ vs NBS-951. Graphical abstract [DISPLAY OMISSION]

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  4. [해외논문]   Uranium bearing dissolved organic matter in the porewaters of uranium contaminated lake sediments   SCI SCIE SCOPUS

    Novotnik, B. (School of the Environment, Trent University, Peterborough, Ontario, Canada ) , Chen, W. (Chemistry and Biochemistry Department, Wilfrid Laurier University, Waterloo, Ontario, Canada ) , Evans, R.D. (School of the Environment, Trent University, Peterborough, Ontario, Canada)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 36 - 44 , 2018 , 0883-2927 ,

    초록

    Abstract Uranium (U) mobility in the environment strongly depends on its oxidation state and the presence of complexing agents such as inorganic carbon, phosphates, and dissolved organic matter (DOM). Despite the importance of DOM in U mobility, the exact mechanism is still poorly understood. Therefore, the aim of our investigation was to characterise sediment porewater DOM in two lakes in Ontario, Canada (Bow and Bentley Lakes) that were historically contaminated with U and propose possible composition of UO 2 -bearing DOM. Depth profiles of U concentrations in porewaters and total sediment digests reveal U levels of up to 1.3 mg L −1 in porewater and up to 0.8 mg −1 g in sediment. Depth profiles of U did not correlate with Fe, Mn, SO 4 2− , or Eh profiles. Therefore, porewater DOM was analysed and taken into consideration as the primary source of U mobility. Porewater DOM in each sediment section (1 cm sections, 20 cm core length) was analysed by high-resolution electrospray ionisation mass spectrometry. PCA analyses of porewater DOM mass spectra showed grouping and clear separation of DOM in sediment sections with elevated U concentrations in comparison to sections with background U concentrations. Several criteria were set to characterise UO 2 -bearing DOM and more than 70 different molecules were found. The vast majority of these UO 2 -DOM compounds fell in the category of carboxyl-containing aliphatic molecules (H/C between 0.85 and 1.2 and O/C ≤ 0.4) and had a mean value of m/z about 720. Highlights U concentrations up to 1.3 mg L −1 in pore waters and 0.8 mg −1 g in sediment are reported for two historically contaminated lakes in Ontario. High resolution mass spectrometry was performed on pore waters. More than 7000 different molecules were evaluated to find UO 2 -bearing dissolved organic matter. Over 70 different UO 2 -bearing molecules had their molecular formula assigned. UO 2 -bearing molecules are plotted in a Van Krevelen diagram according to O/C and H/C ratios. The majority of UO 2 -bearing molecules fell in the category of carboxyl-containing aliphatic molecules with H/C between 0.85 and 1.2 and O/C ≤ 0.4. Size distribution of UO 2 -bearing molecules is presented with a mean size value of m/z of about 720. Graphical abstract [DISPLAY OMISSION]

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  5. [해외논문]   Applicability of the chromium reducible sulfur test for acid metalliferous drainage prediction in hard rock mining   SCI SCIE SCOPUS

    Black, Silvia (ChemCentre, PO Box 1250, Bentley, Western Australia 6983, Australia ) , Allen, David (MBS Environmental, 4 Cook Street, West Perth, Western Australia 6005, Australia ) , North, Michael (MBS Environmental, 4 Cook Street, West Perth, Western Australia 6005, Australia ) , Price, Barry (ChemCentre, PO Box 1250, Bentley, Western Australia 6983, Australia ) , Rothnie, Neil (ChemCentre, PO Box 1250, Bentley, Western Australia 6983, Australia ) , Sharma, Rajesh (ChemCentre, PO Box 1250, Bentley, Western Australia 6983, Australia)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 45 - 53 , 2018 , 0883-2927 ,

    초록

    Abstract The potential for Acid and Metalliferous Drainage (AMD) from waste rock in mining operations is a key issue which must be addressed at all stages, from the initial mining proposal to rehabilitation and site closure. The Chromium Reducible Sulfur (CRS) method was originally introduced into Australia as a rapid and cost-effective method to estimate the acid production potential of acid sulfate soils. However, concerns are being raised over its potentially inappropriate use without supporting scientific evidence to assess the AMD potential of mine wastes in hard rock mining, especially those containing base metal (lead, zinc, copper and nickel) sulfides. This paper outlines the results of a comparative laboratory study of 55 Western Australian mine waste samples and mineral specimens for AMD potential using CRS results from routine commercial laboratories normally handling soil samples as well as conventional approaches. CRS was found to be generally suitable for many applications, particularly for common iron sulfides at low to moderate concentrations (relevant to many iron ore, mineral sands and gold mining operations). However, CRS was not a reliable predictor of potential acid production from samples containing elevated concentrations of iron sulfides, base metal sulfides, arsenopyrite or molybdenite. Issues with CRS precision and bias were also indicated. A good understanding of sulfide mineralogy is required for accurate AMD predictions of these types of mine wastes, and cannot be obtained from any single test. Highlights The CRS method to assess AMD potential has limitations in hard rock applications. CRS variability should be investigated to improve reliability for hard rock. CRS under-reported acid potential for ores containing arsenopyrite and molybdenite. If used, CRS should be combined with NAG testing and mineralogy for AMD prediction.

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  6. [해외논문]   Radium isotope response to aquifer storage and recovery in a sandstone aquifer   SCI SCIE SCOPUS

    Vinson, David S. (University of North Carolina at Charlotte, Department of Geography and Earth Sciences, 9201 University City Blvd, 324 McEniry, Charlotte, NC 28223, USA ) , Lundy, James R. (Minnesota Department of Health, Environmental Health Division, 625 North Robert Street, St. Paul, MN 55164, USA ) , Dwyer, Gary S. (Duke University, Nicholas School of the Environment, Box 90328, Durham, NC 27708, USA ) , Vengosh, Avner (Duke University, Nicholas School of the Environment, Box 90328, Durham, NC 27708, USA)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 54 - 63 , 2018 , 0883-2927 ,

    초록

    Abstract Radium isotopes and water-rock interaction were evaluated in an aquifer storage and recovery (ASR) pilot study conducted in 2010–2011 in Minnesota (USA) in order to identify mechanisms governing Ra activities when low-Ra water is recharged into a sandstone aquifer. Groundwater in the aquifer selected for the study, the Cambrian Mt. Simon Sandstone, contains naturally occurring radium that in many areas exceeds United States drinking water standards (185 mBq/L or 5 pCi/L combined 226 Ra+ 228 Ra), highlighting the need to identify the rates and mechanisms by which stored water acquires Ra isotopes. Major element concentrations of recovered water largely resembled recharged water, while Ra activities exceeded the Ra activities of the recharged water. 224 Ra reached ∼100 mBq/L during the first 8 h of recovery (overall range 15.5–133 mBq/L). 226 Ra and 228 Ra also increased during the 47-day recovery period (23.7–82.5 mBq/L and 33.7–85.5 mBq/L, respectively). Ra isotope ratios indicate the relative contribution of alpha recoil vs. chemical processes (e.g. adsorption/desorption). During recovery, the 224 Ra/ 228 Ra and 228 Ra/ 226 Ra ratios declined, approaching their expected limiting values near unity. Collectively, the rates of Ra activity change with time, trends in Ra isotope ratios, barium concentrations, and manganese concentrations suggest that Ra was governed by chemical processes and alpha recoil, in which the half-lives of each Ra isotope determined the primary mechanism(s) controlling radionuclide mobilization from the aquifer solids. Radium-mobilizing processes during storage may include: (1) recharge of low-Ra water into an aquifer containing high-Ra groundwater induced adsorption/desorption disequilibrium and caused net Ra desorption; (2) chemical conditions during storage (e.g. the Ba content of the recharge water or the reducing conditions in the aquifer) could have further released Ra from the aquifer solids or reduced the effectiveness of Ra adsorption; and/or (3) mobilization from radioactive decay of solid-phase thorium parents (alpha recoil) contributed Ra isotopes into the low-Ra recharge water. The short-lived 224 Ra was released dominantly by alpha recoil while the longer-lived 226 Ra was dominantly released by chemical mechanisms such as desorption. Radium-228, of intermediate half-life, also appears to have been released predominantly by alpha recoil, although significant chemical release of 228 Ra cannot be ruled out. Accordingly, at near-neutral pH, groundwater geochemical conditions (such as redox state and/or shifts in Ra activities or Ba concentrations) can influence observed Ra activities in recovered water, which in proportional terms impart the largest effect on the longer-lived 226 Ra. Given the roles for both alpha recoil and chemical reactions, the duration of storage could influence radium activities in recovered water from ASR wells. Highlights Low-Ra water was stored in a sandstone aquifer and subsequently recovered. Ra isotopes in the recovered water increased during storage. Ra isotope ratios varied during storage, approaching unity with time. Alpha recoil and adsorption/desorption governed observed Ra activity. Ba and Mn suggest Ra was less adsorbed with increasing storage time.

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  7. [해외논문]   Water quality impacts and river system recovery following the 2014 Mount Polley mine tailings dam spill, British Columbia, Canada   SCI SCIE SCOPUS

    Byrne, Patrick (School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, L3 3AF, UK ) , Hudson-Edwards, Karen A. (Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Tremough Campus, Penryn, TR10 9EZ, UK ) , Bird, Graham (School of Environment, Natural Resources and Geography, Bangor University, Bangor, Gwynedd, LL57 2UW, UK ) , Macklin, Mark G. (School of Geography and Lincoln Centre for Water and Planetary Health, College of Science, University of Lincoln, Brayford Pool, Lincoln, Lincolnshire, LN6 7TS, UK ) , Brewer, Paul A. (Department of Geography and Earth Sciences, Aberystwyth University, Penglais, Aberystwyth, Ceredigion, WY23 3FL, UK ) , Williams, Richard D. (School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, UK ) , Jamieson, Heather E. (Geological Sciences and Geological Engineering, Queen's University, Kingston, ON, K7L 3N6, Canada)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 64 - 74 , 2018 , 0883-2927 ,

    초록

    Abstract The Mount Polley mine tailings embankment breach on August 4th, 2014, in British Columbia, Canada, is the second largest mine waste spill on record. The mine operator responded swiftly by removing significant quantities of tailings from the primary receiving watercourse, stabilizing the river corridor and beginning construction of a new river channel. This presented a unique opportunity to study spatial patterns of element cycling in a partially-restored and alkaline river system. Overall, water quality impacts are considered low with Cu, and to a lesser extent V, being the only elements of concern. However, the spatial pattern of stream Cu loading suggested chemical (dominant at low flow) and physical (dominant at high flow) mobilization processes operating in different parts of the watershed. Chemical mobilization was hypothesized to be due to Cu sulfide (chalcopyrite) oxidation in riparian tailings and reductive dissolution of Cu-bearing Fe oxides in tailings and streambed sediments whereas physical mobilization was due to erosion and suspension of Cu-rich stream sediments further downstream. Although elevated aqueous Cu was evident in Hazeltine Creek, this is considered a relatively minor perturbation to a watershed with naturally elevated stream Cu concentrations. The alkaline nature of the tailings and the receiving watercourse ensures most aqueous Cu is rapidly complexed with dissolved organic matter or precipitates as secondary mineral phases. Our data highlights how swift removal of spilled tailings and river corridor stabilization can limit chemical impacts in affected watersheds but also how chemical mobilization (of Cu) can still occur when the spilled tailings and the receiving environment are alkaline. We present a conceptual model of Cu cycling in the Hazeltine Creek watershed. Highlights The Mount Polley mine tailings embankment breach is the second largest on record. Spatial patterns in trace metal cycling were studied in Hazeltine Creek. Water quality impacts are considered low with Cu and V the only elements of concern. Chalcopyrite oxidation and Fe oxide reduction are Cu mobilization mechanisms. Swift removal of spilled tailings can limit chemical impacts in watercourses. Graphical abstract [DISPLAY OMISSION]

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  8. [해외논문]   Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles   SCI SCIE SCOPUS

    Markelova, Ekaterina (University Grenoble Alpes, University Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France ) , Couture, Raoul-Marie (Ecohydrology Research Group, Department of Earth and Environmental Sciences and Water Institute, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada ) , Parsons, Christopher T. (Ecohydrology Research Group, Department of Earth and Environmental Sciences and Water Institute, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada ) , Markelov, Igor (University Grenoble Alpes, University Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France ) , Madé (Andra, National Radioactive Waste Management Agency, R&D Division, Transfer Migration Group, 1/7 rue Jean Monnet, 92298 Chatenay Malabry Cedex, France ) , , Benoit (Ecohydrology Research Group, Department of Earth and Environmental Sciences and Water Institute, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada ) , Van Cappellen, Philippe (University Grenoble Alpes, University Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble) , Charlet, Laurent
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 75 - 88 , 2018 , 0883-2927 ,

    초록

    Abstract Argillaceous geological formations are considered promising repositories for waste containing inorganic contaminants. However, the sequestration capacity of an argillaceous natural barrier may change as a result of dynamic environmental conditions, in particular changes in redox state. Here, we imposed redox cycles to argillaceous suspensions amended with a mixture of the inorganic contaminants As(V), Sb(V), Cr(VI), by alternating 7-day cycles of sparging with either oxic or anoxic gas mixtures. During the redox cycles, we assessed the relative importance of different contaminant sequestration mechanisms under sterile and non-sterile conditions. The non-sterile experiments were carried out 1) with the argillaceous material as is, that is, containing the native microbial population, 2) with the addition of ethanol as a source of labile organic carbon, and 3) with the addition of both ethanol and a soil microbial inoculum. In order to capture the observed solid-solution partitioning trends, a series of mixed thermodynamic-kinetic models representing the dynamic conditions in the experiments were developed using PHREEQC. Parameter values for processes such as adsorption, which occurred in all experiments, were kept constant across all the simulations. Additional formulations were introduced as needed to account for the microbial detoxification and respiration of the contaminants in the increasing complexity experiments. Abiotic adsorption of As and abiotic reductive precipitation of Cr dominated sequestration of these two contaminants under all experimental conditions, whereas the presence of microorganisms was essential to decrease the aqueous Sb concentration. Once reduced, As(III), Sb(III), and Cr(III) were not re-oxidized upon exposure to dissolved O 2 in any of the experiments. Neither the mineralogy nor the native microbiota catalysed contaminant oxidation processes. Thus, kinetically, the reduction of As(V), Sb(V), and Cr(VI) was irreversible over the experimental duration (49 days). The capacity of the argillaceous matrix to reduce and sequester the aqueous contaminants, without subsequent remobilization to the aqueous phase during the oxic periods, supports the use of argillaceous barriers for geologic waste storage. Highlights Aqueous As(V) is removed by adsorption, Cr(VI) by abiotic reductive precipitation. Microorganisms remove aqueous Sb(V) via reductive precipitation. Once reduced, As(III), Sb(III) and Cr(III) are not oxidized when exposed to O 2 . Oxyanions are reduced in parallel via detoxification, sequentially via respiration. Measured E H does not respond quantitatively to observed speciation of Cr, N, As, Sb. Graphical abstract [DISPLAY OMISSION]

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  9. [해외논문]   From swollen gels to dried films: Relating the IR spectra of ferrihydrite dried as a film on an ATRIR crystal to aqueous suspensions   SCI SCIE SCOPUS

    Hamid, Rossuriati Dol (School of Chemistry and Environmental, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450, Shah Alam, Selangor, Malaysia ) , Miskelly, Gordon M. (School of Chemical Sciences, University of Auckland, Private Bag, 92019, New Zealand ) , Hadzir, Nursyamsyila Mat (School of Chemistry and Environmental, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450, Shah Alam, Selangor, Malaysia ) , Mohamad Hanapi, Nor Suhaila (School of Chemistry and Environmental, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450, Shah Alam, Selangor, Malaysia ) , Swedlund, Peter J. (School of Chemical Sciences, University of Auckland, Private Bag, 92019, New Zealand)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 89 - 96 , 2018 , 0883-2927 ,

    초록

    Abstract In aquatic systems ferrihydrite forms as highly porous aggregates that resemble swollen gels. Much insight into the surface chemistry of ferrihydrite has been gleaned using a technique in which ferrihydrite is dried on to the surface of a crystal that acts as an Attenuated Total Reflectance (ATR) medium for in situ infrared (IR) studies of ligand sorption. In this paper BET N 2 adsorption, acid-base titration, H 4 SiO 4 isotherms and the relationship between H 4 SiO 4 sorption and H 4 SiO 4 interfacial oligomerization are used to systematically probe the influence of this drying step on ferrihydrite's surface chemistry. This means that insights into sorption reactions revealed from in situ ATR-IR are can be increasingly related to real environmental systems. Comparing the measured acid-base titration curves to the theoretical curve provide a specific surface area (SSA) estimation of ≈600 and 290 m 2 g −1 for the fresh and film-dried ferrihydrite respectively, compared to the BET N 2 adsorption values of 240 and 140 m 2 g −1 where the fresh ferrihydrite was freeze dried prior to BET measurement. The H 4 SiO 4 isotherms were identical on the two ferrihydrite samples when normalized to the titration derived surface areas. The extent of interfacial H 4 SiO 4 oligomerization provides insights into surface structures. Within experimental uncertainty, the process of drying ferrihydrite into a film did not alter either the general trend in the relationship between sorption and oligomerization, or the extent of oligomerization as a function of surface coverage normalized to the titration derived surface areas. Therefore, in comparable laboratory studies where sorption densities for dried films are compared with fresh suspensions the SSA values of 290 and 600 m 2 g −1 respectively should be a reasonable estimate. Highlights The chemistry of H 4 SiO 4 on ferrihydrite suspensions and dried films are compered. This connects insights from ATRIR spectra to insights from batch suspensions. Acid-base titrations, N 2 BET, H 4 SiO 4 isotherms and IR spectra were compared. Both ferrihydrites had similar behaviour when normalized to titration derived SSA. This implies similar ferrihydrite short range order before and after film formation.

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  10. [해외논문]   Mineralogical influences on water quality from weathering of surface coal mine spoils   SCI SCIE SCOPUS

    Clark, Elyse V. (Department of Crop and Soil Environmental Sciences, 185 Ag Quad Lane, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA ) , Daniels, W. Lee (Department of Crop and Soil Environmental Sciences, 185 Ag Quad Lane, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA ) , Zipper, Carl E. (Department of Crop and Soil Environmental Sciences, 185 Ag Quad Lane, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA ) , Eriksson, Kenneth (Department of Geosciences, 926 West Campus Drive, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA)
    Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry v.91 ,pp. 97 - 106 , 2018 , 0883-2927 ,

    초록

    Abstract Surface coal mining fractures geologic materials to access coal seams. The excavated rock materials (mine spoils) have freshly exposed mineral surfaces that weather rapidly and release soluble ions to streams during and after site reclamation. The soluble ion release is directly influenced by the mine spoil mineralogy. We examined relationships among mine spoil mineralogical and geochemical properties and soluble ion release for the purpose of determining their influence on Appalachian stream water quality. We determined the mineralogy, bulk spoil composition, leachate concentrations, and acid-base accounting (ABA) parameters of 16 non-acid-forming spoil samples. Mineralogical composition was determined using thin section spectroscopy, a column leaching experiment was conducted to determine eluted leachate concentrations of 15 elements, and ABA parameters were determined using conventional methodologies. Results indicated that the mine spoils were comprised predominantly of quartz, with smaller amounts of plagioclase and K-feldspars, lithic metamorphic fragments, muscovite, chlorite, and goethite. Cementing agents included quartz, kaolinite, siderite, and carbonate. Indicators of weathering observed in samples presumed to be unweathered included halloysite at the expense of feldspar and goethite at the expense of pyrite and siderite. On an oxide basis, SiO 2 and Al 2 O 3 dominated the bulk geochemical composition. Sulfate had the largest initial leachate concentration whereas HCO 3 − was the dominant anion in final leachates. The ABA tests indicated most spoils were non-acid-forming, with total sulfur values ranging from 0.01 to 0.38%. Relatively high dissolved sulfate elution was attributed to trace pyrites. Carbonates were not observed in many samples, indicating other mineral sources neutralized the acid produced by pyrite oxidation. Feldspar hydrolysis and the weathering of metamorphic lithic fragments (schists), chlorite, and muscovite may have been responsible, in part, for soluble ion release and acid-neutralization. Bulk Mg contents often exceeded Ca for most samples, and high Mg:Ca ratios in leachate concentrations relative to regional waters may be attributed to chlorite weathering. Historically, high levels of soluble ion release was assumed to be controlled by sulfide oxidation reactions coupled with carbonate neutralization reactions. These results, however, indicate that other minerals typically presumed to be relatively stable also contribute significantly to overall soluble ion release in this highly disturbed environment. Minimizing the amount of time water is in contact with mine spoils and, by extension, decreasing the potentials for chemical weathering, may assist with controlling soluble ion discharges from Appalachian coal mining areas. Highlights Appalachian coal mine rock mineralogy influences water quality and chemistry. Quartz, feldspars, lithics, muscovite and chlorite comprised spoil mineralogy. Typically unreactive minerals influenced mine spoil leachate geochemistry. Non-acid-forming spoils were influenced by pyrite oxidation and neutralization. Feldspar, muscovite, and chlorite weathering influenced dissolved ion release.

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