Quantification and fractionation of mercury in soils from the Chatian mercury mining deposit,southwestern China |
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Authors: | Yonghua Li Linsheng Yang Yanfang Ji Hongfei Sun Wuyi Wang |
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Institution: | (1) Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A Datun Road, Anwai, Chaoyang District, Beijing, 100101, China |
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Abstract: | Contents of total Hg and Hg fraction, organic matter, pH, grain size and chemical composition were measured to investigate
the pollution characteristics and binding behavior of Hg in soils collected from the Chatian Hg mining deposit (CMD), southwestern
China. The average concentration of Hg concentration in the CMD soils was 155 and 1,315 times higher than that in control
soils and Chinese soils, respectively, suggesting that the CMD soils were heavily contaminated by the element. The finding
was confirmed by Müller geoaccumulation index assessment with 75% very seriously polluted, 6.25% highly to very highly polluted
and 18.75% moderately to highly polluted. Hg sources in the region were natural and anthropogenic: in addition to the pedogenic
process and original geochemical situation, human mining–refining activities have also seriously impacted the redistribution
of Hg in soils, especially in paddy soils. Based on the BCR protocol, soil Hg was divided into exchangeable (EXC), amorphous
Fe–Mn oxides (AFe–MnOX), organic-crystalline iron oxides (OM-CFe) and residual (RES) fraction. The average percentage of the
four fractions in the CMD followed the trend: RES (85.77%) > OM-CFe (12.44%) > AFe–MnOX (0.93%) ≥ EXC (0.86%), suggesting
that the majority proportion of soil Hg in the study area remained of residual form inside the soil mineral matrix. However,
their concentrations and percentages significantly varied among different locations and land use types. Soil physico-chemical
parameters were key factors affecting the presence of Hg fraction. Generally, Hg fraction concentrations were positively correlated
with the sand contents and soil pH values, which was presumably due to the basic anthropogenic input of Hg-containing materials
and their similarity to sand in physical characteristics. However, organic matter caused adsorption–fixation and reduction–volatilization
to coexist, which had opposite effects on Hg concentrations in soil, consequently exhibiting its dual nature. |
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