Transport and fate of mercury under different hydrologic regimes in polluted
stream in mining area |
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Authors: | Yan Lin Thorj?rn Larssen Rolf D Vogt Xinbin Feng and Hua Zhang |
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Institution: | 1. Department of Chemistry, University of Oslo, POB 1033, 0315 Oslo, Norway 2. Department of Chemistry, University of Oslo, POB 1033, 0315 Oslo, Norway;Norwegian Institute for Water Research, Gaustadalleen 21,0349 Oslo, Norway 3. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China |
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Abstract: | Seepage from Hg mine wastes and calcines contains high concentrations of mercury (Hg). Hg pollution is a major environmental
problem in areas with abandoned mercury mines and retorting units. This study evaluates factors, especially the hydrological and
sedimentary variables, governing temporal and spatial variation in levels and state of mercury in streams impacted by Hg contaminated
runo . Samples were taken during di erent flow regimes in theWanshan Hg mining area in Guizhou Province, China. In its headwaters
the sampled streams/rivers pass by several mine wastes and calcines with high concentration of Hg. Seepage causes serious Hg
contamination to the downstream area. Concentrations of Hg in water samples showed significant seasonal variations. Periods of
higher flow showed high concentrations of total Hg (THg) in water due to more particles being re-suspended and transported. The
concentrations of major anions (e.g., Cl??, F??, NO3?? and SO4
2??) were lower during higher flow due to dilution. Due to both sedimentation
of particles and dilution from tributaries the concentration of THg decreased from 2100 ng/L to background levels (< 50 ng/L) within
10 km distance downstream. Sedimentation is the main reason for the fast decrease of the concentration, it accounts for 69% and 60%
for higher flow and lower flow regimes respectively in the upper part of the stream. Speciation calculation of the dissolved Hg fraction
(DHg) (using Visual MINTEQ) showed that Hg(OH)2 associated with dissolved organic matter is the main form of Hg in dissolved
phase in surface waters in Wanshan (over 95%). |
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Keywords: | mercury hydrology temporal variation fractionation and speciation |
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