Distribution And Uncertainties Evaluation Of Soil Heavy Metals In Yixing,Yangtze River Delta,China

The study on the distribution characteristics and uncertainty of heavy metals in soil can accurately control the pollution of soil heavy metals of the region.This paper chooses Yixing as the study area,which located in Yangtze River Delta,analyzes the distribution characteristics and uncertainty of soil heavy metals,and provides scientific evidence for soil pollution prevention,protection,and regional sustainable development improvement.The paper evaluated the grade of soil heavy metal pollution by Nemerow index and potential ecological risk assessment.And then,used the inverse distance weight interpolation to show the results.The spatial variability of heavy metals in soil was explored by using the statistical tools.Take soil Hg content as an example,discussed uncertainty of spatial multi-points joint probability by using sequential Gaussian conditional simulation.Subsequently,threshold exceedance distribution of six soil heavy medal contents under the conditional of critical probability.The conclusions obtained in this paper are as follows:(1)The results of Nemerow index of soil heavy medals show that the As and Pb pollution of Yixing was trifling,98.18%and 99.91%of sampling points was sorted to Grade I,respectively.The single factor pollution index of Cd,Cu and Zn shows that there are some areas with medium and heavy degree of pollution.The light,moderate and severe pollution levels of Nemerow index accounted for 2.42%,0.61%and 0.52%,respectively.The main pollution in the study area is Cd,followed by Cu and Zn.(2)The results of potential ecological risk assessment of soil heavy metals show that the single factor potential ecological risk grade of As,Pb and Zn is low,and heavy metal ecological risk of the soil,Cd>Hg>Cu.The latent ecological risk degree of soil Cd is comparatively serious.Area of heavy risk multiple factors,which is mainly around the urban construction land in southwest and northwest.(3)The statistical analysis of heavy metal content in soil shows that the variation of As,Cu,Pb and Zn in the study area are in strong variation,which indicates that the variables of the study area are affected by many factors.Cd and Hg belong to strong variation,which indicates that these two kinds of heavy metals are affected by human factors.Spatial autocorrelation of six soil heavy medals are as follows:As>Cu>Cd>Pb>Hg>Zn.The most suitable models of six kinds of heavy metals are exponential models,and the Semi-variogram function of Cd,Hg and Pb are similar.Hg is isomorphic,while there is obvious heterogeneity in As from south to north,and in Cu from northeast to southwest.(4)Uncertainty analysis of heavy metal content in soil shows that,soil As content of the surface plots is higher than the background value due to the long-term accumulation.The random factors of Cu and Hg are huge,the heavy metal pollution is mainly caused by solid waste stacking.Soil Cd content is related to industrial wastewater discharge,Pb and Zn are mainly related to the accumulation of pollutant emissions from vehicles.