Soil Heavy Metal Pollution Characteristics And Risk Of A Contaminated Site In Shanghai

This paper takes a contaminated site in Taopu Industrial Park,Shanghai as an example,selects soil in different depths of the site as the research object,combines field observation,laboratory analysis,multivariate statistics,model simulation and other methods and techniques.The spatial distribution of copper(Cu),chromium(Cr),cadmium(Cd),arsenic(As),lead(Pb),zinc(Zn)and nickel(Ni)in the soil of the research site,the source analysis of heavy metals,soil environmental quality assessment and human health risk assessment were systematically analyzed.It provides key basic data support for the subsequent restoration of contaminated sites and the redevelopment and redevelopment of contaminated sites.The main conclusions are as follows:(1)The average contents of Cu,Cr,Cd,As,Pb,Zn and Ni in the site were 31.40mg/kg,83.43mg/kg,0.44mg/kg,7.84mg/kg,29.38mg/kg,47.13mg/kg and 98.67mg/kg,respectively.Except As,the average contents of the other 6 heavy metal elements were1.15,1.19,3.17,1.18,1.58 and 1.21 times of the background values of Shanghai soil,respectively.(2)Through the enrichment factor method,it is found that all heavy metal elements in the study site are basically enriched in a depth range of 0-140 cm under the influence of human activities,showing relatively obvious enrichment.Through principal component analysis,the further source analysis of the heavy metal elements in the research site found that Cu,Cd and Pb were from the industry-traffic source;As and Zn come from industrial production or discharge,while Cr and Ni mainly come from natural soil-forming process.(3)The specific situation of soil pollution in the study site was revealed through the single factor pollution index method,Nemerow comprehensive pollution index method and potential ecological risk index method.The comprehensive degree of heavy metal pollution in the soil of the site was severe pollution,among which Cd was severe pollution and other elements were mildly polluted.The comprehensive potential ecological risk in the site is between low risk and medium risk,among which the potential ecological risk degree of Cd is the highest,and the ecological risk of other heavy metal elements in the study site is in a low risk state.In summary,the site is faced with severe pollution situation,and Cd is the key pollutant in the site.(4)By scenario prediction method,the concentration values of 7 heavy metal elements in this research site are predicted year by year for the next 30 years from2020 under optimistic scenario and non-mutation scenario.The results show that except Cd,the other 6 heavy metal elements all show a trend of decreasing gradually with the increase of time under any scenario.However,Cd accumulates in the soil in the range of 0-100 cm depth under the scenario of no mutation that is closer to the reality,and the predicted concentration value is higher than the measured value in 2020.It is inferred that further Cd accumulation in the surface soil in the study site is still certain to occur in the future,leading to the deterioration of soil environmental quality.(5)Using the predicted value of the mutation-free scenario as input data,the Cal TOX model was used to evaluate the health risk of the target pollutant Cd in this study site.The results found that during the 30 years from 2020 to 2049,the cancer risk for children and adults was consistently above the threshold,representing unacceptable health risks.