| Every year,a large amount of expired or decommissioned ammunition in China needs to be destroyed and disposed of,and the soil environment in the destruction area is suffering from serious heavy metal pollution,and the ecological safety of the surrounding area is also facing a great threat.The investigation and remediation of heavy metal pollution in ammunition destruction sites has become a current research hotspot in the field of heavy metal pollution investigation,assessment and remediation.This thesis takes an ammunition destruction site in Shanxi as the research object,and evaluates the pollution degree and potential ecological hazards of soil heavy metals through sampling and investigation and monitoring analysis,analyses the morphological distribution and biological availability of Pb,Cu,Zn and Sb in different sampling areas,evaluates the model to assess the health risks of Pb,Cu,Zn and Sb,and explores the remediation pathways of heavy metals in the study area.The main findings are as follows:（1）The average contents of Cr,Ni,Cu,Zn,As,Cd,Sb and Pb in surface soil samples of the study area were 91.95,26.15,991.50,2515.03,8.04,0.85,112.56 and 4739.97 mg/kg,which were higher than the background values in Shanxi Province.In addition,it is 0.37,0.14,9.92,8.38,0.32,1.42,3.22,27.88 times of the corresponding screening values.The destruction activities lead to an obvious increase in heavy metal content in the study area,in which the pollution of Pb,Cu,Zn,Sb and Cd is more serious,and the pollution of Cr,As and Ni is less.The potential ecological hazards of heavy metals such As Pb,Cu and Sb show a strong risk level,Cd is a strong risk level,and Cr,Ni,As and Zn are a slight risk level.The potential ecological hazard index of the study area was as high as 2653.35,which was 4.42 times of the upper limit of the extreme risk level.The sources of heavy metals Ni,Cd,Zn,Cr and Cu in the study area were mainly mixed sources,and their contribution rates were 78.04%,62.84%,53.25%,43.21%and 40.86%,respectively.The main sources of Pb and Sb are incineration and destruction sources,whose contribution rates are 72.94%and 53.99%respectively.The contribution rate of natural sources to As is the largest,which is 44.63%.（2）Pb,Zn,Cu and Sb accounted for 80.6%,81.7%,83.2%and 82.1%,respectively.There were some differences in other forms.The potential risk in the study area came from high iron-manganese oxide binding heavy metals.The bioavailability of Pb,Zn,Cu and Sb were all lower than 20%,and the bioavailability of heavy metals was closely related to their morphology.Based on the total amount of heavy metals,the non-carcinogenic risks of Pb,Cu,Zn and Sb for adults were 11.1,0.34,0.09 and 2.42,and for children were 102,3.16,0.8 and 21.33,respectively.However,when calculated based on the content of bioavailable forms,The non-carcinogenic risks of Pb,Cu,Zn and Sb for adults were 0.008,0.004,0.005 and 0.15,respectively,and those for children were 0.07,0.04,0.05 and 1.42,respectively.The human health risks based on the total amount of heavy metals were several orders of magnitude higher than those based on bioavailability.They overestimate their risk.In terms of carcinogenic risk,based on the total amount calculation,the carcinogenic risk of Pb for adults is 3.21×10-4,and that for children is 2.99×10-3.The carcinogenic risk of Pb for adults is1.90×10-5and that for children is 1.77×10-4 when calculated based on the content of bioavailable forms.（3）The content of Pb,Cu,Zn and Sb in the soil treated with zeolite,biochar and their combined application decreased,while the residual state increased.The combined application had the best effect,and the available state contents of Pb,Cu,Zn and Sb were reduced by 7.83%,0.73%,1.90%and 0.36%,respectively.After the application of amendments,the toxic leaching content of heavy metals also decreased,and the combined application effect was the best.The TCLP leaching contents of Pb,Cu,Zn and Sb decreased by 33.8%,38.6%,58.4%and 3.35%respectively.The results of heavy metal immobilisation on the surface of biochar also show that the porous structure and large specific surface area of biochar can immobilise some of the heavy metals. |
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