| Coal occupies a dominant position in China's energy consumption structure.The exploitation and utilization of coal resources lead to a series of ecological and environmental problems,such as surface subsidence,land destruction,vegetation damage,water and soil pollution and so on.Especially in the mining areas with high diving level in the east of China,the long-term coal mining subsidence has formed a large area of surface water.The characteristics of heavy metal pollution in coal subsidence areas have attracted more and more attention from many researchers.Antimony is a semi-volatile harmful heavy metal,coal combustion is an important source of antimony in the environment.And antimony and its compounds are widely distributed in the atmosphere,soil,water and other environments.At present,the environmental pollution of antimony is becoming more and more serious.In this study,the distribution characteristics of antimony content in water samples of coal mining subsidence areas in Huainan during high and low water periods were analyzed,and then the Guqiao coal mining subsidence area was selected as the key research area.Overlying water(n=10),middle water(n=10),lower water(n=10)and surface sediment(n=10)samples were collected in the Guqiao coal mining subsidence water body.The surface sediments were centrifuged to obtain the corresponding pore water samples(n=10).The Sb in these samples were analyzed by Atomic Fluorescence Spectrometry(AFS),The occurrence forms of heavy metal As,Sb in surface sediments of Guqiao were determined by BCR three-step extraction method,with an aim of evaluating the associated pollution degree of heavy metals by methods of heavy metal pollution index and geo-accumulation index.The following results were obtained.(1)During the dry season,the content of antimony in the water body of coal mining subsidence area in Huainan city was 1.18-7.24 ?g·L-1,the average value was 3.37 ?g·L-1,and the content range of antimony in 42 surface water samples of Huainan City during the high water period was 0.01-9.98 ?g·L-1,with an average value of 3.04 ?g·L-1.The maximum sampling point was located in Guqiao Mine.Compared with the background value of the source area of the Yangtze River,there is a certain enrichment phenomenon of Sb in stratified water body.(2)Compared with the China sediment and the Huainan soil background values,As,Cd,Cu,Cr,Mn,Ni,Sb were enriched in the studied sediment samples.It is noted that the average content of Sb was as high as 1.66 mg·kg-1 respectively.The results of BCR extraction showed that the average ratio of residual state to total amount of Sb was 77.74%.(3)The distribution of heavy metals obeys the following order:sediment>pore water>overlying water.There is obvious migration activity of Sb in overlying water and sediment in Guqiao subsidence area.The distribution characteristics of eight heavy metals in sediment,pore water and overlying water are also consistent.(4)The results of heavy metal pollution index method showed that the total value of HPI of eight heavy metals in overlying water of Guqiao coal mining subsidence area was lower than the critical value of pollution,and there was no risk of heavy metal pollution.Geo-accumulation index revealed that the order of ecological risk of heavy metals follows as Cd>Cr>Sb>Cu>As>Ni = Mn>Zn where and Cr need attentions from environmental managers.Sb is slightly polluted,and the proportion of moderate pollution is 20%and 10%respectively. |
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