| With the rapid development of China’s social economy and urbanization,industrial enterprises in succession,but also bring the urban environment pollution,to improve the quality of urban environment,the reform of the urban economy in our country,the implementation of "half astern into three" "enterprises entering into the area" industrial adjustment policy,early due to some technical backwardness,lack of environmental awareness leads to serious pollution enterprise down or moved,appeared a number of existing pollution conditions of the industrial enterprise legacy,urban environment pollution problem is becoming more and more serious.When the remaining contaminated sites are redeveloped and utilized,heavy metal pollutants will have a certain impact on the site environmental media and may cause harm to the health of the surrounding people.Since 2011,the State Council and the Ministry of Environmental Protection have issued a series of documents,repeatedly emphasizing the need to strengthen the supervision of the environment of contaminated sites,and the reuse of contaminated sites must carry out standardized and targeted environmental risk assessment.In this paper,heavy metals in the soil of a lead battery plant in Suzhou were taken as the research object.The main content of the research was to analyze the distribution of heavy metal concentration,draw a three-dimensional volume rendering map based on single heavy metal concentration and further analyze the main sources of heavy metals in each layer of soil.Evaluate the degree and potential risk of heavy metal pollution;Health risk assessment of heavy metals was carried out based on four-step method and the slice map of spatial distribution of health risk was established.Based on the above research contents,the following conclusions are drawn:(1)The concentration of lead and arsenic was over 50%.The concentrations of other 5 heavy metals Cu,Ni,Cd,Hg and Cr(Ⅵ)were all lower than the limit.In combination with Voxler’s three-dimensional spatial distribution map of concentration,it was found that most of the points seriously polluted by Pb and As were located in the southeast direction of the site.(2)Based on principal component analysis to extract the 3 principal components,the results show that the first and second principal components of the cumulative contribution rate is high,Cu,Pb,Cd in the first principal component have higher load,Pb,Cd from the former lead battery factory manufacturing battery for long lead dust,lead emissions from waste water and waste containing cadmium cell stabilizer,the influence of human activity disturbance,concluded that the first principal component is likely to be for the source of "human" and "natural source" to review the source;In the second principal component,As and Hg have higher positive loads,and part of As comes from natural sources.Hg is mainly affected by atmospheric deposition after human burning coal,and is classified as "natural source".The third principal component,Ni may be the joint action of "natural source" and "influence of soil parent material".(3)The results of Nemero comprehensive pollution index showed that more than95% of the sites were polluted to different degrees,and the longitudinal pollution degree of points S-5,S-11 and S-14 was larger than that of other sites,and the soil at a depth of 0.5m～3.0m was more seriously polluted.According to the geological accumulation index method,the results show that the pollution degree and data span of Cd and Pb are large,and the corresponding evaluation grades are distributed from 0 to 6.The total number of samples with the geological accumulation index of Pb in moderate pollution,heavy pollution and heavy pollution accounts for 79.0%.The sampling sites of serious pollution accounted for 11.3%,which was the highest among the six heavy metals.(4)According to the evaluation results of the potential ecological harm index model,the potential ecological harm index values of Pb and Cd have a large span,and the maximum value appears at S14-1,which is 0.5m above the surface of this point.This depth is most seriously polluted by lead and cadmium.According to the total ecological harm RI calculated at each point point,there were 6 soil points that reached a strong degree of potential harm,among which the RI of S-14 point was as high as2048.02,exceeding the limit value of 1200 for strong harm,indicating a strong potential harm to the surrounding soil environment and even other environmental media and organisms.(5)The heavy metal pollutants of concern in this site were determined to be heavy metals Pb,Cd,Cu and similar metals As in the soil.As and Cd were selected to study their carcinogenic risks to children and adults,and As,Pb,Cd and Cu were selected to study their longitudinal health risk distribution maps of non-carcinogenic risks for children and adults.The results showed that the high carcinogenic and noncarcinogenic risk values of As in the surface samples of 0.5m and 1.5m of soil in the residual site mainly appeared at the points of S-4,S-11 and S-14.The carcinogenic risk of CD(CR)and non-carcinogenic risk(HI)appear at the S-14 location,and the area with this point as the source of pollution is relatively large.The value of CR is in the range of 10-6 to 10-4,which will bring a certain carcinogenic risk to human body.The non-carcinogenic risk of Pb to adults can be ignored,but the non-carcinogenic risk to children is relatively large at each sampling depth,among which the lead pollution at S-14 point is particularly serious,and the non-carcinogenic risk to children at 0.5m and1.5m reaches 4-5 times of the acceptable level.Based on the above results,the soil of the lead battery plant has been polluted by heavy metals of As,Pb and Cd to different degrees,and the pollution is mainly at the depth of 0.5～1.5m.From the three-dimensional spatial distribution of soil heavy metal concentration,the risk distribution can be directly and vividly determined,mainly in the main production workshop and wastewater treatment area of lead battery plant.The Nemero pollution index method and geoaccumulation index method were used to evaluate the heavy metal pollution in each layer of soil,which showed the pollution level more comprehensively,and confirmed that the pollution degree of a certain layer of soil depth was serious.Drawing the soil heavy metal spatial health risk map makes the risk visualization,and visually identifies the health risk distribution characteristics of each soil depth,which is of great significance for the formulation of soil remediation plan and soil management in the later stage. |
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