The Study On Heavy Metal Pollution In Urban Soils Of Dongyang River Basin

With the discharge of industrial pollutants,the excessive use of fertilizers and pesticides and fertilizers in agricultural production,and the random dumping of rural living pollutants,heavy metals enter,migrate and accumulate in the soil.However,heavy metals migrate slowly and most of the heavy metals are concentrated in the soil,resulting in soil pollution Increasingly.This paper is based on the Sample data which 4295 surface soils heavy metals and Remote Sensing date of land use types in the Dongyang River Basin,using GIS,Geo-statistical analysis,and Pollution Evaluation index methods,reveal the heavy metal arsenic(As),mercury(Hg),chromium(Cr),copper(Cu),lead(Pb),cadmium(Cd),nickel(Ni),and zinc(Zn)pollution characteristics,spatial distribution pattern and major sources of heavy metal pollutants in the soils of surface soil,research shows:(1)The spatial distribution of the heavy metals in the middle and western parts of the Dongyang River Basin is relatively high.From the vertical distribution,the heavy metals other than Zn generally show a decreasing trend as the height increases,and the distribution of exceeding standard soil heavy metals in the areas of altitudes from 200m to 400m in the local area of Chian Town,Fotang Town,Hengdian Town,Choujiang Street and Geshan Town,are mostly distributed in Yiwu City,only a few are distributed in Dongyang City.The soil heavy metals in the Dongyang River Basin are mainly within the primary and secondary grades.(2)The spatial correlation of soil heavy metal content in the river basin is above the medium level,the nugget coefficient of all heavy metal elements in the fitted semi-variance model does not exceed 75%,and only Cd,Pb,and As three soil heavy metal nuggets coefficient is higher than 39%.(3)The average values of soil heavy metals As,Hg,Cr,Cu,Pb,Cd,Ni,and Zn were all within the national secondary standards,but the maximum value exceeded 2.27 to 12.84 multiple than the national secondary standard.The Coefficient of Variation of Cd greater than l,mean it's a strong variability,except for the remaining heavy metals of Cd which are moderately variable.CV order of the eight heavy metals is:Cd>Ni>Cr>Hg>As>Pb>Cu>Zn.(4)The evaluation results of the single factor index and the Nemerow index show that the integrated pollution level in the study area is not high.Cd is light and moderately polluted,and Hg is lightly polluted,Other heavy metals are Mainly clean.The results of the Geo-accumulation index and ecological risk index show that the pollution degree of heavy metals in the soil in Dongyang River Basin are inconsistent.That is to say,when analyzing the heavy metal pollution of soil in Dongyang River Basin,the focus will be different,and pollution assessment results will differ.However,the three evaluation results all indicate that the soil pollution of heavy metal Cd is high.(5)Different types of land use in the Dongyang River basin will affect the distribution of heavy metal content in the soil,and the major sources of heavy metal pollutants in the soil can be roughly analyzed.The landscape pattern index in dryland,paddy field,residential area,and traffic land has a significant correlation with the pollution degree of various heavy metals.Agriculture,domestic pollution,and transportation are the factors causing soil pollution.In summary,combined with the Dongyang River Basin ecological health report and field exploration findings,the soil heavy metal pollution in Dongyang River Basin is mainly distributed in Beiyuan Street,Duanjiang Street,Futangjie Town,Chian Town,and Qiangcheng Street in Yiwu;the main factors are:Fertilizers and pesticides are used in large quantities,agricultural non-point source pollution is serious,industrial enterprises are numerous,total industrial pollution is large,and domestic sources of pollution(urban and rural)emit large amounts.