Health Risk Assessment And Pollution Characteristic Of Heavy Metals In Subsidence Area In Huainan Coal Mining Area

Taking the six subsidence ponds in the Huainan coal mining area(two new mines,two middle-aged mines and two elderly mine)as the main research object,a total of 90 water,sediments and surrounding soil samples from six subsidence ponds were took.Through the analysis of the samples,the characteristics of heavry metals of water bodies,soil and sediments were analyzed.Content of heavy metal in different media and their relationship with the physical and chemical properties were considered.The pollution load index,geo-accumulation index and potential ecological risk index were used to compute pollution state of heavy metals in soil and sediment.In this paper,single factor index and Nemero index of pollution were employed to comprihensively assess pollution state of heavy metals.Finally,USEPA model was used to assess health risk of heavy metals in the water bodies.Main results were as follows:(1)The average concentration of heavy metals in soil around the collapse pond and in the sediments were relatively low.Their values was lower than the background value of soil in Huainan and the secondary standard of soil environment quality standard of China,except the average concentration of Mn in partial sediments.For the surrounding soils of different subsidence periods,concentrations of the other heavy metal from the middle age mine area were highest except for Cr.For the average concentrations of Cd,Cu and Zn in the soils from different years,the turn from high to low was in turn middle mine> old mine> new mine,while that of Cr?Mn?Ni and Pb was middle mine> new mine> old mine.Contents of heavy metal in the sediments from the differnet periods showed irregular changes.(2)For the surrounding soils of the ponds,there was a significant correlation among Pb,Cu and Cr,there was also a significant correlation among Cu,Cr,Mn and Ni,and showed that the source of Cu,Cr,Mn,Ni and Pb may be the same.For the sediments,there was a significant correlation among Cu,Zn and Ni;the same was to Mn,Ni and Pb.Pb and Cu had a significant correlation.Above results showed that the source of Cu,Zn,Ni,Mn and Pb may be the same.From the correlation analysis between heavy metals and physical-chemical properties,different heavy metals were affected by different physical-chemical properties.(3)The paper employed the pollution load index and index of geo-accumulation method to evaluate heavy metal pollution in the surrounding soil and sediments.The results showed that the pollution degree of all samples belonged to the lowest level.For the ecological risk assessment,ecological risk coefficients of Cd in the soils surrounding pond and sediment samples were greater than those of the other heavy metals,however,its pollution degree belonged to slight pollution according to the ecological harm relation table.The comprehensive ecological hazard index(RI)of seven heavy metals in each sampling point was non pollution or slight pollution in the corresponding relation table.(4)The single factor index method and Nemero comprehensive index method were used to evaluate the pollution status of heavy metals in water bodies.The results showed that the pollution index of Hg was the highest.In the six subsidence ponds,heavy metal pollution in Xinji'er Mine was the most serious.For the health risk assessment results,the health risks of heavy metals in the water bodies of the six subsided ponds were within the acceptable range.According to the calculated results of health risk values,the carcinogenic health risk played a decisive role in the overall health risk.Moreover,the results showed that the carcinogenic health risk values of As and Cr were relatively high,and that of Cd was the low.Figure [4] table [33] reference [84].