| Harbin is a typical area crisscrossed with rapid urbanisation and agricultural intensive management.Agricultural planting and industrial production can cause soil heavy mental pollution.Taking the surface soil in the Fourth Ring Road of Harbin as the research object,125 soil samples were taken to determine the total content of heavy metal manganese,Fe,Cu,Zn,As and Pb in the soil,compared and analysed the heavy metal content in the 2nd ring,the 2nd ring-the 3rd ring and the 3rd ring-the 4th ring,and analysed the correlation between heavy metals.Combined with Arc Gis 10.4 software,the spatial distribution map of soil heavy metals was drawn to carry out quality evaluation,ecological risk evaluation and human health risk assessment of the soil environment in the study area.The main research work and results are as follows:（1）The average concentration of Cu,Zn and Pb exceeds the soil background value,which is 1.64,1.29 and 1.31 times the soil background value respectively,and there are more excess rates of Cu,Zn and Pb.The mean change of Cu,Zn content is the same,and it gradually increases from the inner rings to the outer ring.The average value of Pb content is sorted in order:2 rings>2-3 rings>3-4 rings,which are all higher than the soil background value.The average enrichment coefficients of Cu,Zn and Pb are 1.67,1.31 and 1.34,which are in a mild enrichment level.The average enrichment coefficient of As is 0.97,which is close to 1 and almost consistent with the natural background.However,there are Cu and Zn severe enrichment points in the research area.（2）There are many similarities between the spatial distribution characteristics of Cu,Zn and Pb elements.At the intersection of Hatong Expressway and Harbin Ring Expressway,Changjiang Road and Pioneer Road,Beijing-Harbin Expressway and Suiman Expressway,they all show high-content areas,which may be related to the automobile park distributed on Xianfeng Road and the relatively large number of vehicles entering and leving.（3）The average value of the heavy metal accumulation index of Mn,Fe,Zn,As and Pb is less than 0,which is a pollution-free level.The average single-factor pollution index of Mn and As soil heavy metals is 0.99 and 0.95 respectively,which is in the degree of no pollution.Cu,Zn and Pb are 1.64,1.29 and 1.31 respectively,all of which are between1-2 and are in a slight pollution level.The average evaluation result of the Nemero Comprehensive Pollution Index is 2.06,which is a moderate pollution degree,but the excess rate of the sampling point in the research area is 94.4%,and there is a degree of heavy pollution in each ring.（4）The average value of the potential ecological risk index of Cu,Zn,As and Pb is8.20,1.29,9.52 and 6.53 respectively,which is in a slight pollution level;the average value of the comprehensive potential ecological risk index is 26.52,and the research area as a whole is in a slight pollution level.（5）In the human health risk assessment,the average non-carcinogenic risk value of Cu,Zn,As,and Pb is less than 1,from large to small is As>Pb>Cu>Zn,and the total value of the four elements HQ is also less than 1,indicating that there is no non-carcinogenic risk of heavy metals in the research area.The average carcinogenic risk of As and Pb is2.34×10-5 and 3.77×10-7 respectively,and the average carcinogenic risk of As is greater than 10-6,indicating that there is a potential carcinogenic risk. |
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