Spatial Distribution Of Heavy Metals And Health Risk Evaluation Of Farmland Soils Around A Metal Smelter In Inner Mongolia

To explore the spatial distribution pattern of soil heavy metals in the farmland around a metal smelter is of vital importance to realize the rational use of regional soil resources and to prevent and control pollution.In this thesis,we use classical statistics,geostatistics and machine learning to analyze the accumulation and spatial distribution of As,Pb,Cr and Cd elements in the soil,and use correlation analysis,cluster analysis and principal component analysis to analyze the sources of soil heavy metal pollution,based on the Nemero integrated pollution index method,potential The pollution level and human health risk were evaluated and discussed based on the Nemero integrated pollution index method,the potential ecological hazard index method and the carcinogenic and non-carcinogenic risk methods.The main conclusions of this thesis are as follows:1、The content of As,Cr,Pb and Cd in the soils around the metal smelters ranged from 2.31 to 29.58 mg-kg-1,26.61 to 105.94 mg-kg-1,6.20 to 74.39 mg-kg-1 and 0.01 to2.29 mg-kg-1,respectively,and all the heavy metals in the study area were smaller than the risk screening value for soil pollution on agricultural land and the risk control value for soil pollution on agricultural land.Except for As,the mean values of all heavy metals were higher than the background values of the Hetao irrigation area to varying degrees,especially Cr,Pb and Cd,which were 3.5,0.66 and 0.23 times higher than the background values of the Hetao irrigation area,respectively.2、The spatial distribution characteristics of soil heavy metal contents predicted based on ordinary kriging and random forest models were generally similar,with the high value of soil Cd mainly distributed near the smelter,and the trend of decreasing with increasing distance in the southeast direction,while soil Pb,As and Cr generally showed a trend of high in the north and low in the south,and the accuracy of the random forest model was higher than that of the ordinary kriging method.3、Through correlation analysis,cluster analysis and principal component analysis,it was inferred that there are two main sources of heavy metal pollution around the smelter: first,soil Cd,Pb and As due to anthropogenic factors caused by human mining and smelting processes;second,soil Cr influenced by natural factors of weathering and soil formation of the parent rock.4、Taking the background value of the soil in the river-loop irrigation area as the standard,the PN shows that the percentage of heavy,moderate and light heavy metal pollution in the agricultural soil around the smelter is 37.95%,27.59% and 30.17%respectively,and the overall level of pollution is light or heavy.11.20% of the sample sites have strong RI index pollution,of which 0.86% and 10.34% are very strong and strongly polluted respectively.The main focus is on minor to moderate potential ecological risk contamination,which needs to be taken seriously and prevented and protected.The results of the health risk assessment of heavy metals in the smelter soil showed that the elements Cd and Cr in the soil around the smelter posed a high carcinogenic risk to human beings,and corresponding measures should be taken.