Distribution,Sources And Risk Assessment Of Heavy Metals In Soils Of Fengle River Watershed,Huizhou District

Soil is an essential component of the earth and provides the basis for human activities.Heavy metal pollution in soil is widespread all over the world and has seriously affected the ecological environment and human health,which have been the common focus in modern society.Therefore,this study systematically investigates the distribution,sources,pollution degree and risk characteristics of heavy metals in topsoil,which could provide theoretical and practical references for local governments to control soil heavy metal pollution.In this study,taking the Fengle River Watershed of Huizhou District as an example,topsoil samples were collected from different functional areas,and the concentration of As,Cd,Co,Cr,Cu,Mn,Ni,Pb and Zn were determined.Several pollution evaluation methods such as Nemerow pollution index,enrichment factor and geo-accumulation index,and data analysis methods such as correlation analysis,principal component analysis,PMF model,potential ecological risk and health risk assessment were used for the distribution,source analysis,pollution degree and risk assessment of heavy metals.The main results are as follows:(1)The distribution of soil heavy metals content was investigated,and it was found that the average contents of As,Cd,Cu and Zn in the study area exceeded the soil background value in Anhui province.The highest concentrations of As,Cr,Cu and Ni were found in the water-reservoir area,while the highest concentrations of Cd and Pb were found in the plain area.The highest concentrations of Co,Mn and Zn were found in the forest area.(2)The sources of soil heavy metals in the study area were apportioned.It was found that Pb was primarily from traffic emissions,As was mostly derived from industrial activities,Cd was mostly from agricultural activities,and Co,Cr,Cu,Mn,Ni and Zn mainly originated from natural sources.The contribution rates of the four sources were 5.4%,10.0%,19.2%and 65.3%,respectively.(3)Using the comparison of soil heavy metal pollution degree among different functional areas,the results of Nemerow pollution index showed that water-reservoir area was the most polluted.The pollution index,enrichment factor and geoaccumulation index showed that As and Cd were the most polluted of the nine heavy metals.(4)The risks of soil heavy metals were analyzed in different functional areas.The results indicated that the potential ecological risk was moderate,and that the ecological risk due to Cd was the largest of the nine heavy metals,with agricultural activities as the largest contribution source.The results of health risk assessment revealed that oral ingestion was the main exposure route.Among nine heavy metals,the non-carcinogenic risk of As was highest,while the carcinogenic risk of Cr was highest.It was observed that the health risks of children were higher than those of adults,and industrial activities were the main contributor to carcinogenic risk.For non-carcinogenic risk,industrial activities were the largest source in forest area and water-reservoir area,while traffic emissions were the largest source in plain area.