| With the continuous development of social economy,the problem of environmental pollution is increasingly aggravated,and the situation of soil environmental pollution is gradually deteriorating.As a representative of the typical soil pollution of mining area of the surrounding soil heavy metal pollution and its pollution situation is not optimistic,the long-term cumulative effects of heavy metals soil environmental health risks caused by the problem is more serious,so the surrounding soil heavy metal content,source and environmental risks,for the prevention and control of regional soil heavy metal pollution has important practical significance.In western arid and natural geographical conditions in arid areas with strong representativeness,the mining area in Xinjiang,Inner Mongolia,Gansu and other surrounding soil heavy metal pollution were studies,but relatively lack of Ningxia for studies of the surrounding soil,based on the typical copper-silver mining area in Ningxia and the surrounding soil on the surface as the research object,combined with the natural geographical features in the study area layout 194 sampling points,on every point sampling and heavy metal content determination of system science.Respectively using The Single Factor Index Method,The Nemerow Pollution Exponential Method and The Muller's Accumulated Index of heavy metal pollution evaluation way for the mining area and the surrounding soil heavy metals pollution degree evaluation,and through the GIS space mapping,geographical probe analysis and resolution of positive definite matrix molecules PMF source of soil heavy metal source analysis methods of soil heavy metals in the study area discriminant analysis of characteristics of spatial distribution and pollution source,finally using the method of potential ecological risk assessment and the human health risk assessment in our country RAG-C model of the soil heavy metal elements in the study area the ecological health risk assessment,The pollution characteristics,sources and ecological health risks of heavy metals in the soil in the study area were analyzed comprehensively,and the following conclusions were drawn.(1)The study area soil heavy metal Hg,As,Cu,Zn,Cr,Cd,Pb,Ni and Ag elements of descriptive statistical analysis,the results showed that the average nine kinds of heavy metal content in soil were not beyond the soil environmental quality standard of controlling farmland soil pollution risk(GB15618-2018)the risk of filter value,Hg,Cd,Pb and Ag elements are higher than the average of soil background values of heavy metals in Ningxia,including Hg paint is most serious,followed by Pb,Ag and Cd respectively..Among the nine heavy metal elements in the soil,the maximum values of As,Cu,Cd and Pb all exceeded the risk screening values of soil environmental quality agricultural land soil pollution risk control standard(GB15618-2018),and the exceeded rates were 0.52%,0.52%,1.03%and 1.03%,respectively.The results showed that the accumulation of Hg,Cd,Pb and Ag existed in most regions of the study area,and the content of As,Cu,Cd and Pb in the soil at some points had exceeded the corresponding risk screening value,it was necessary to further strengthen soil environmental monitoring at the corresponding points.(2)The soil background values of heavy metals in Ningxia as evaluation criteria,using a variety of pollution evaluation method to evaluate the soil heavy metal pollution situation in the study area,the analysis results show that the single factor pollution index method,Hg and Ag and Cd of sampling points of heavy metal pollution accounted 100%,99.48%and 99.48%respectively,and Cd and Hg,Ag has a trend of regional pollution;Pb,Cr,As,Cu and Zn all have some pollution in different degree.The results of The Nemerow Pollution Exponential Method show that the proportion of heavy pollution level is 91.2%,and the proportion of moderate pollution level is 8.76%,indicating that the large area is heavily polluted,some of them are moderately polluted,and there are no clean samples,indicating that the heavy metal pollution is quite serious.The results of the Muller's Accumulated Index show that the proportion of heavy metal pollution at the sampling points of Hg,Ag and Cd are 100%,94.85%and 74.2%,respectively;As,Cu,Cr and Pb are 0.52%,1.03%,1.03%and 8.25%respectively,and Zn and Ni are clean.In general,the evaluation results of Hg,Ag and Cd elements show that the proportion of heavy metal pollution points is very high,presenting a situation of surface source pollution.As,Cu,Cr and Pb all have some sample points to the extent of heavy metal pollution,and the point source pollution is obvious,which indicates that the pollution situation of heavy metal in the soil in the research area is relatively serious,and necessary measures should be taken to reduce the harm of heavy metal pollution.(3)In order to realize the accurate prevention and control of soil heavy metal pollution,further analyzing the source and contribution of heavy metals in the study area,the main use of PMF source of quantitative analysis combined with GIS spatial visualization,and refer to the geographical detector interaction analysis,parsing out four kinds of soil heavy metal total contribution source,Factor 1 is a natural source of parent material,the relationship between rock soil parent material in the study area is larger,the main contribution of elements for Cr and Ni,contribution of 56.8%and 57.8%respectively;Factor 2 traffic activities and for industry wastewater irrigation comprehensive source,silver and copper in the southwest of the study area,south mining ore mining,transport and mineral intergrowth and the Middle East in the study area a large pool of water irrigation on the surrounding farmland irrigation,the influence of its contribution to the more heavy metal element for the As,Cu,zinc,and Pb,contribution were 76.6%,67.5%,54.9%and 60.5%respectively;Factor 3 is the atmospheric subsidence source and industrial emission source,which is related to the mining and dressing of the mining areas in the southwest and south of the research area,and is also related to the surrounding industrial and mining enterprises,coal combustion and metal smelting.The main element contributed is Hg,with a contribution of 77.2%.Factor 4 was determined as the source of agricultural activities,and the main contributing elements were Ag and Cd,with contribution degrees of 53.3%and 40.4%,respectively.It was related to the dressing of sand and gravel and the application of phosphorous fertilizer in the selenium melon field in the study area.(4)Ecological risk and human health risk were evaluated respectively for heavy metals in the soil of the study area.Among them,according to potential ecological risk assessment,Hg is the degree of extremely high ecological risk,Cd and Ag are medium ecological risk,and the remaining 6 heavy metals are mild ecological risk.According to the analysis of the proportion of pollution points,Hg presents an overall pollution situation,while Ag,Cu and Pb all present a part of ecological hazard state,and As,Zn,Cr and Ni have a good ecological environment pollution situation.Integrated ecological risk analysis in the high ecological risk of 72.7%,higher ecological risk of 22.7%,moderate ecological risk of 4.6%,and that the region ecological risk is extremely high,and the harm of the regional ecological environment situation is not optimistic.The health risk assessment of soil heavy metals showed that the average value of the 6 heavy metals in the study on the total non-carcinogenic quotient(HQ total)of human health in this region was 0.048,which was less than the assessment baseline value,indicating that the non-carcinogenic risk of the 6 heavy metals in the soil had a small impact,but it was still necessary to pay attention to the impact of exposure route through oral intake.Total carcinogenic risk(CR total)in the study are a of the mean value of 1.55×10-5,the result is higher than the acceptable values,this area of soil heavy metals in carcinogenicity,approaches of exposure to oral intake,As and Cr element is the main risk factors of cancer,the Cd is part of the sample have a higher risk,in order to ensure the safety of soil environmental quality and human health,the need to strengthen the risk of cancer of the As and Cr,reasonable and effective soil As and Cr element pollution prevention measures. |
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