Evaluation Of Soil Heavy Metal Pollution And Identification Of Potential Soil Pollution Areas Around Metal Mining Areas In China

While the development of the metal mining industry brings economic growth,the frequent mining activities also inevitably lead to the accumulation of heavy metal contaminants in the soil and an increased risk of environmental degradation in the surrounding areas of mining areas.Previous studies on heavy metal contamination in soils due to metal mining usually required extensive field investigations and experiments,consuming large amounts of human and material resources.Moreover,previous studies often focused on a single or a few metal mining areas,and the results usually did not provide sufficient spatial information to support the analysis of solving soil environmental quality problems around mining areas on a national scale.In this study,the following data were first obtained through literature surveys and web data crawling techniques: 2086 sets of regional soil heavy metal concentration data around metal mining areas nationwide,information on 2088 metal mining areas currently under operation nationwide(e.g.,the scale of mineral resource reserves and the latitude and longitude coordinates of the center of mining areas),and spatial datasets of relevant natural and human environmental factors in China.Then,the comprehensive index method was used to evaluate the environmental capacity of soil heavy metals in the areas affected by metal mining activities around metal mining areas nationwide,and the regional soil heavy metal pollution status around metal mining areas was analyzed.Subsequently,the Max Ent(Max Ent＿MRS)model based on the scale of mine reserves was proposed to spatially predict the probability of soil heavy metal pollution in China’s metal mining industry and compare its prediction accuracy with that of Max Ent.The spatial distribution of potential soil heavy metal pollution areas was clarified,and the main environmental influencing factors on the probability of pollution occurrence were explored,along with a quantitative evaluation of their relationship.The main conclusions of this study were as follows:(1)Compared with the risk reference values of heavy metal elements in Chinese soil,except for Hg,Ni,Cr and Cu,the average soil concentrations of the other five heavy metal elements As,Cd,Zn,and Pb are 1.4 times,6.7 times,1.6 times,and 1.4 times the reference values,respectively.Therefore,under the long-term impact of mining activities,the concentrations of heavy metals in the soil around China’s metal mining areas have significant accumulation,especially the Cd element in the soil.(2)In China’s central region,the heavy metal elements in the soil around mining areas with negative existing environmental capacity are As,Cd,Pb,and Zn.In eastern and southern China,they are As,Cd,Cu,Pb,and Zn.In southwestern China,they are As,Cd,Cu,Hg,Pb,and Zn.Compared with other regions,these areas have the highest number of heavy metal elements with negative existing environmental capacity,indicating more severe and complex soil heavy metal pollution.(3)Overall,the comprehensive environmental capacity index of soil heavy metals is higher in the north and lower in the south,with overloaded and warning areas(i.e.areas with serious soil pollution)mostly appearing in the surrounding areas of southern mining areas.(4)In identifying potential soil heavy metal pollution areas in the metal mining industry,the prediction accuracy of the Max Ent＿MRS model(AUC = 0.822)is higher than that of Max Ent(AUC = 0.807).Among the natural and human environmental factors,GDP,population density,soil type,annual average precipitation,and land use type are the main influencing factors on the occurrence probability of soil heavy metal pollution in the metal mining industry.(5)The spatial distribution of the probability of soil heavy metal pollution deriving from metal mining industry shows that the regions with the occurrence probability of soil heavy metal pollution higher than 54% are mainly concentrated in the eastern coastal provinces of China and Guizhou Province,Jiangxi Province,central Guangxi Province,southeastern Sichuan Province,Gansu Province and southern Shanxi Province,Liaodong Peninsula,Shandong Peninsula and the border areas of Shandong,Anhui and Hebei and Hubei.The occurrence probability of soil heavy metal pollution tends to be higher than 54% in regions that meet the following conditions of natural and human environmental factors: GDP,76-261,267 million yuan/km~2;population density,152-551 people/km~2;precipitation,924-2869 mm/year;soil type,Ferralisols or Luvisols;land use type,construction land,urban land and other Construction land(quarry,large industrial area,factory and mine,etc.)...