Study On The Methyl At Ion Of Mercury And Its Influencing Factors In Soil In Coal Mining Subsidence Area

As the most important primary energy in China,coal had a serious impact on the environment and ecology after a long period of extensive coal mining.The subsidence of the ground and the accumulation of waste rock pile in the process of coal mining,processing and transportation have seriously affected the local environment,and the heavy metal pollution has become one of the hot spots in the study of many scholars.Mercury is a highly toxic element that can be transformed into a more toxic neurotoxin methylmercury in a wide range of environments.Methylmercury is easy to accumulate in body fat.In the environment,it can enter the human body through the food web,which is harmful to human health.It is easy to accumulate water in the subsidence area and eventually form water area from subsided land because of high phreatic water level in Huainan.The land environment was transformed into an aquatic environment,after the soil subsides,and the surface soil turn into the sediment at the bottom of water area from subsided.Therefore,the distribution characteristics of mercury and methylmercury in the soils in the subsidence area of Huainan Coal Mining Area were explored,which provided a scientific basis for the prevention and control of mercury pollution and comprehensive utilization of soil in the subsidence area.In this study,the soil in the subsidence area of Huainan coal mining was studied.The temporal and spatial distribution characteristics of mercury and methylmercury in soil from the subsidence area were systematically analyzed.On this basis,the factors that affect the distribution of mercury and methyl mercury in soil of the subsidence area are discussed in combination with soil physical and chemical properties,and the risk of soil mercury in the subsidence area is evaluated.The main results are as follows:(1)The mercury contents in the subsidence area of coal mining in Huainan is between 0.011 and 0.050 mg/kg,with an average value of 0.027 mg/kg,which is 1.35 times the background value of the soil in Huainan City and 1.43 times that of the unsinked soil.It shows that after soil subsidence,the soil mercury content increases,and there is a potential ecological risk to some extent.(2)Comparing the soil mercury contents in different subsidence years,it was found that with the increase of the subsidence years,mercury enriched in the soil and the mercury was mainly concentrated in the surface of the subsidence area,reflecting that the soil mercury in the subsidence area may mainly come from atmospheric deposition.(3)The average MeHg contents in the surface soil of Huainan Guqiao,Panyi,Pansan and Xinzhuangzi coal mining subsidence areas was 0.24 ng/g,0.09 ng/g,0.21 ng/g,and 0.08 ng/g,respectively.With the increase of the age of subsidence,the methylmercury contents is significantly reduced.In the vertical section,methylmercury is mainly concentrated in the soil surface and decreases with increasing soil depth.And the soil organic matter and soil pH in the subsidence area are one of the main factors controlling the change of methylmercury content in the subsidence area.(4)Two kinds of pollution assessment methods(single factor pollution index method and potential ecological risk index method)were used to evaluate soil mercury in coal mining subsidence areas in Huainan.The results shows that,he pollution index of mercury in the coal mining subsidence area is 1.64,the pollution level is light pollution,and the potential risk coefficient is 56.17,which is a moderate ecological hazard.The average soil pollution index of Gu Qiao coal mining subsidence area is 2.21 of moderate pollution,and the average value of potential risk coefficient Eri is 88.4,and it is in strong ecological harm.Therefore,enough attention should be paid to it.