Sediment geochemistry and arsenic mobilization in shallow aquifers of the Datong basin,northern China |
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Authors: | Xianjun Xie Yanxin Wang Mengyu Duan Huaiqing Liu |
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Institution: | (1) Key Laboratory of Biogeology and Environmental Geology of Ministry of Education, China University of Geosciences, Wuhan, 430074, People’s Republic of China |
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Abstract: | Understanding the mechanism of arsenic (As) mobilization from sediments to groundwater is important for water quality management
in areas of endemic arsenic poisoning, such as the Datong basin in northern China. The bulk geochemistry analysis of sediment
samples from three 50-m boreholes drilled specifically for this study at As-contaminated aquifers, the groundwaters of which
have an As concentration up to 1060 μg/l, revealed that the average bulk concentrations of major and trace elements of the
samples are similar to those of the average upper continental crust. The average As content of the sediment samples (18.7 mg/kg)
is higher than that of modern unconsolidated sediments (5–10 mg/kg). Moreover, the abundance of elements varied with grain
size, with higher concentrations in finer fractions of the sediments, such as silt and clay. The concentration of NH2OH–HCl-extracted iron (Fe) strongly correlated with that of extracted As, suggesting that Fe oxyhydroxides may be the major
sink of As in the aquifer. The results of microcosm experiments showed that As mobilization from sediments to groundwater
is probably mainly related to changes in the redox conditions, with moderately reducing conditions being favorable for As
release from sediments into groundwater. |
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Keywords: | Aquifer sediments Arsenic Datong basin Geochemistry Mobilization Redox condition |
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