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Kim D.-M.,Korea University | Kim D.-M.,Mine Reclamation Corporation MIRECO | Yun S.-T.,Korea University | Yun S.-T.,University of Calgary | And 3 more authors.
Chemical Geology | Year: 2014

A shallow (<25m), coastal alluvial groundwater system underneath a paddy field in the Yangyang area of South Korea was investigated to examine the occurrence of redox processes. The aquifer is affected by seawater intrusion, and is characterized by a highly reducing environment facilitated by high organic matter in the sediments. Hydrochemical data with δ34S and δ18O of sulfate were examined for depth-specific groundwater from two multilevel samplers that were installed at seaward (YY2) and landward (YY1) locations. Shallow groundwater showed distinct patterns of redox zoning. Evidence of significant bacterial sulfate reduction (BSR) was observed throughout the nearly entire depths of the two boreholes, while at the depths of active seawater intrusion in YY2, conditions suitable for methanogenesis were never reached. Thus, at YY2 the deep zone of intense BSR was overlain by a zone in which methanogenesis occurred in a low-sulfate environment. In contrast, concurrent BSR and methanogenesis in YY1 occurred at depths with high sedimentary organic matter and low dissolved sulfate due to intensive BSR. Considerable BSR in the groundwater representing trapped seawater in a clay layer had resulted in a very strong increase of δ34Ssulfate up to 99.9‰. The inferred sulfur isotopic enrichment factor (ε) for BSR in the lower part of YY2 was -12.3‰, while ε at YY1 was much higher (-45.9‰). In addition, the observed trends of δ18Osulfate at YY1 indicated significant oxygen isotope exchange of sulfate-oxygen with ambient water, likely because of lower cell-specific rates of BSR and higher sulfur isotope fractionation as indicated by the δ34S. In contrast, there was little evidence of oxygen isotope exchange between water and SO4 2- at YY2. This study indicates that in coastal aquifers with sulfate-reducing activity, δ34S and δ18O of sulfate can reveal zones of active seawater intrusion and of trapped seawater. This study provides an example of the application of sulfur and oxygen isotope data with hydrochemical and hydrogeologic data to interpret complex redox zonation in an organic-rich coastal environment. © 2014 Elsevier B.V.

Kwon J.C.,Sejong University | Lee J.-S.,Mine Reclamation Corporation MIRECO | Jung M.C.,Sejong University
Applied Geochemistry | Year: 2012

A national-scale survey of the environment in and around mines was conducted to evaluate the status of total As contamination in agricultural soils surrounding numerous abandoned metal mines in Korea. This survey aimed to compare As concentrations in soils in relation to geology and mineralization types of mines. A total of 16,386 surface soil (0-15cm in depth) samples were taken from agricultural lands near 343 abandoned mines (within 2km of each mine). These samples were decomposed by aqua regia and analyzed for As by AAS with a hydride-generation (HG) device. To compare As levels in soils meaningfully with geology and mineralization types, three sub-classification criteria were adapted: (1) five mineralization types, (2) four valuable ore mineral types, and (3) four parent rock types. The average concentration of As in all the soils was 11.6mgkg -1 with a range of 0.01-4230mgkg -1. Based on the mineralization types, average As concentrations (mgkg -1) in the soils decreased in the order of pegmatite (18.2)>hydrothermal replacement (14.5)>sedimentary deposits (12.4)>hydrothermal vein (10.7)>skarn (4.08). In terms of the valuable ore mineral types, the concentrations decreased in the order of Sn, W, Mo, Fe and Mn mines>Au, Ag, and base metal mines>Au and Ag mines≈base metal mines. For parent rock types, soils from metamorphic rocks and heterogeneous rocks exhibited enhanced As levels related to both igneous and sedimentary rocks. Therefore, it can be concluded that soils from highly altered rocks subject to metamorphic and igneous activities contained relatively high concentrations of As in the surface environment. © 2011 Elsevier Ltd.

Ko M.-S.,Korea Institute of Science and Technology | Kim J.-Y.,Gwangju Institute of Science and Technology | Park H.-S.,Mine Reclamation Corporation MIRECO | Kim K.-W.,Gwangju Institute of Science and Technology
Journal of Cleaner Production | Year: 2015

Arsenic (As) immobilization in soil using acid mine drainage sludge (AMDS) is described following batch, column, and field experiments. The AMDS is a by-product from electrochemical treatment of acid mine drainage and mainly contains Fe-oxide. Batch experiments were carried out to determine optimum mixing ratio of AMDS for As immobilization. Continuous flow column experiments were carried out to identify the optimal excavation method and field experiments were used to assess As immobilization efficiency and feasibility. In the batch experiments, the optimum mixing ratio was determined to be 3.0 wt%. Column experiments indicated that the surface soil amendment was adequate for As immobilization. In the field experiments, the average As concentration in pore water was observed to be 4.9 μg L-1 at the immobilization layer, and 11.6 μg L-1 at the contaminated layer in the AMDS amended plot. In addition, rice grain contained 0.06 mg kg-1 of As. The XANES analysis confirmed that As(V) was the main species in the soil and rice grain. These results indicated that soil amendment with AMDS could induce As immobilization in soil, and prevent As transfer from soil to pore water and crops. © 2015 Elsevier Ltd. All rights reserved.

Lee S.H.,Gwangju Institute of Science and Technology | Kim J.-Y.,Gwangju Institute of Science and Technology | Kim H.A.,Gwangju Institute of Science and Technology | Kim K.-W.,Gwangju Institute of Science and Technology | And 4 more authors.
Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment | Year: 2012

In order to remove arsenic, adsorption methods are widely used because of its cost-effectiveness and installation convenience. In this study, yttrium based adsorbents such as yttrium carbonate, yttrium hydroxide and titanium-loaded yttrium carbonate are tested to develop highly selective adsorbent for the removal of arsenic. Yttrium hydroxide showed the best removal efficiency on arsenite removal whereas Ti-loaded yttrium carbonate showed the best removal efficiency on arsenate removal because of enhanced surface area. These results suggested that yttrium based materials could be effective adsorbents for arsenic removal from water. © 2012 Taylor & Francis Group.

Ko M.-S.,Gwangju Institute of Science and Technology | Park H.-S.,Mine Reclamation Corporation MIRECO | Kim K.-W.,Gwangju Institute of Science and Technology | Lee J.-U.,Chonnam National University
Environmental Geochemistry and Health | Year: 2013

Bioleaching of As from the soil in an abandoned Ag-Au mine was carried out using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A. ferrooxidans is an iron oxidizer and A. thiooxidans is a sulfur oxidizer. These two microbes are acidophilic and chemoautotrophic microbes. Soil samples were collected from the Myoungbong and Songcheon mines. The main contaminant of the soil was As, with an average concentration of 4,624 mg/kg at Myoungbong and 5,590 mg/kg at Songcheon. A. ferrooxidans and A. thiooxidans generated lower pH conditions during their metabolism process. The bioleaching of As from soil has a higher removal efficiency than chemical leaching. A. ferrooxidans could remove 70 % of the As from the Myoungbong and Songcheon soils; however, A. thiooxidans extracted only 40 % of the As from the Myoungbong soil. This study shows that bioleaching is an effective process for As removal from soil. © 2013 Springer Science+Business Media Dordrecht.

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