Heavy Metal Pollution And Ecological And Health Risk Assessment Of Soils And Sediments In Northwest China

In recent years,with the rapid development of mining industry and urban industrialization,the economic level has been greatly improved,but the harmful gases and liquids emitted by mining and industrial development pollute the surrounding environment and endanger human health.Therefore,in this paper,the soil around a tailings pond in Longnan,Gansu Province,Northwest China,and the sediments of Bahe and Chanhe rivers in Xi'an are taken as the research objects.Through the determination of the concentrations of heavy metals in the sample soil and sediments,several pollution assessment methods(Geological accumulation index method,Nemero index method and potential risk assessment method)are used to assess the heavy metal pollution level in the study area Finally,the sources of heavy metals in the study area were determined by multivariate analysis(correlation analysis and principal component analysis)(1)The content of Sb,As and Hg in the soil of the study area exceeded the background value of the local soil,and the closer the heavy metals were to the mining area,the higher the concentration of heavy metals was;except Cd,the highest concentration of heavy metals was found in the sediment,and the coefficient of variation of other heavy metals except Pb showed that the heavy metals might be affected by exogenous factors.(2)Through the analysis of geological accumulation index,Nemerow index and potential ecological risk assessment,it was found that the pollution of heavy metal Sb in the soil of the study area was relatively serious,and the main contribution rate of comprehensive potential ecological risk accounted for 65.12%.Combined with the analysis of coefficient of variation,it was obviously related to the degree of human interference.In the sediments of the study area,only Cd was slightly polluted,and the rest of heavy metals were almost non polluted,and the pollution of heavy metals was relatively high 77% of the total potential ecological risk.(3)By combining the "guidelines" and USEPA model to evaluate the soil and sediment in the study area,it is found that the health risk assessment model formulated by the "guidelines" concludes that as in the soil of the study area has carcinogenic health risk under three different exposure routes,and the rest of heavy metals do not have carcinogenic health risk,but through USEPA The results of the two models are almost the same,but the final evaluation results are different,which is due to the different carcinogenic risk values given by the two methods at home and abroad.Both of the two health risk assessment methods have come to the conclusion that oral intake is the most important way for human health risk caused by heavy metals in soil and sediment.