| 【Purpose】The contents and distribution of Pb,Cd and Cr in the soil of Wujiang District,Suzhou City were investigated to evaluate the pollution degree and potential ecological risk,to analyze the environmental impact factors of soil heavy metal content,and to provide the relevant basis for the early warning and prevention of soil pollution in the area.【Methods】In this study,the contents and distribution of Pb,Cd and Cr in the soil of Wujiang District,Suzhou City were measured by site investigation,field GPS positioning sampling,laboratory atomic absorption analysis method.The environmental pollution factors of soil heavy metals were systematically evaluated by single factor pollution index method,Nemero comprehensive pollution index method and potential ecological risk index method.We used ArcGIS mapping software to map the distribution,and used statistical methods to analyze the environmental impact factors of soil heavy metal content.【Result】①The pH value of the soil in the study area ranged from 3.33 to 7.24 with an average value of 5.50,which was mostly acidic and strongly acidic.Pb,Cd and Cr were 11.8%,66.7% and 29.2%,respectively,which were the average contents of three kinds of heavy metals in soil secondary environmental quality standard.There were 22 points Cd content in the 120 samples of the monitoring sites exceeded the secondary standard,the excessive rate was 18.3%,and the Pb and Cr contents did not exceed the secondary standard.②From the distribution of townships,the average content of soil lead in each township is from high to low order: Zhenze> Taoyuan> Lili(Fenhu Development Zone)> Pingwang> Shengze> Tongli> Qidu> Songling;The average content of soil cadmium is from high to low order:Zhenze> Taoyuan = Shengze> Pingwang> Lili(Fenhu Development Zone)= Tongli> Qidu> Songling;The average content of soil chromium from high to low order: Taoyuan> Tongli> Lili(Fenhu Development Zone)>Pingwang> Shengze> Qidu> Songling.③The results of the statistical study show that the production and discharge of industrial waste and industrial wastewater will affect the pH value of farmland soil in the area,and the daily output of industrial waste is negatively correlated with soil pH;The daily output of industrial wastewater at all points was weakly correlated with soil Pb content;The generation and discharge of industrial wastewater will affect the Cd content of farmland soils in the area;The production and discharge of industrial wastewater will affect the Cr content of farmland soil in the area,and the daily output of industrial wastewater is positively correlated with the Cr content in farmland soil.④The results of single factor pollution index show that two sites are moderately polluted by Cd,the pollution rate is 1.67%,20 points are slightly polluted by Cd and the pollution rate is 16.7%;The results of Nemero comprehensive pollution index show that11 sites are mildly polluted by heavy metals,the pollution rate is 9.17%,and 20 sites reach the heavy metal pollution warning limit,the warning rate is 16.7%.⑤The potential ecological risk coefficient of Pb and Cr in rural soil of Wujiang District of Suzhou City was grade Ⅰ and the harm degree was low;Cd has 10 sites of single factor potential ecological risk coefficient for grade Ⅱ to achieve moderate ecological hazards,accounting for 8.3% of the total sample number.The total potential ecological risk coefficient RI was grade Ⅰ and the harm degree was low.⑥According to the analysis of the present situation of soil pollution in Wujiang district of Suzhou City,it is speculated that the heavy metal pollution and accumulation in this area may be due to the industrial activities of township industrial enterprises,especially the sewage discharge.In this regard,we proposed three ecological countermeasures:source control,scientific treatment;engineering measures to reduce the pollution of landfill leachate;improving plant remediation measures. |
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