Comparison of risk assessment based on the various methods of heavy metals in soil: A case study for the typical field areas in the Jianghan Plain
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摘要: 以江汉平原典型场区周边农田土壤为研究对象，分析了土壤重金属元素Cd、Pb、As、Hg的总量和赋存形态特征，选用修正单项污染指数法、潜在生态风险指数法、风险评估编码法(RAC)和次生相与原生相比值法(RSP)四种评价方法开展了土壤重金属的污染风险评价，并对评价结果进行了对比讨论。分析结果表明：（1）基于总量的两种方法对比，潜在生态风险指数法优于修正单项污染指数法。（2）基于形态的两种方法对比，RAC法的评价结果比RSP法更为合理。（3）基于总量和形态方法对比，潜在生态风险指数法和RAC法各有其优缺点，潜在生态风险指数法能直观反映重金属在土壤中的富集信息和环境危害性，而RAC法则可以利用形态来阐明重金属在土壤环境中的行为特性和生态活性。因此，在进行土壤重金属污染风险评价时，综合考虑重金属种类、累积程度、生物毒性和生物可利用性等参数指标，才能更加科学准确地评估重金属在土壤中的环境风险。综合上述评价结果，江汉平原典型场区周边农田土壤重金属元素Pb、As污染程度较低，对周边环境无影响；重金属元素Hg累积程度不高，但由于其具有较高的生物毒性，对周边环境存在潜在威胁；重金属元素Cd是研究区最主要的污染因子，对周边环境影响大，亟需采取相应措施减轻Cd带来的风险。Abstract: In this paper, the total amount and speciation characteristics of heavy metals (Cd, Pb, As and Hg) in agriculture soil in typical field areas in the Jianghan Plain are analyzed by field sampling and laboratory analyses. Four evaluation methods, including the fixed single pollution index method, the potential ecological risk index method, the risk assessment coding method (RAC) and the phase and primary comparison method (RSP), are chosen to carry out the risk assessment of heavy metals in soil, and the evaluation results are discussed. The results show that (1) compared with two total amount methods, the potential ecological risk index method is superior to the modified single pollution index method. (2) Compared with two speciation methods, the evaluation result of the RAC method is more reasonable than that of the RSP method. (3) Compared with total methods and morphological methods, the potential ecological risk index method and the RAC method have their advantages and disadvantages. The potential ecological risk index method can directly reflect the enrichment information and environmental hazards of heavy metals in soil, and the RAC method can use morphology to elucidate the behavior and ecological activity of heavy metals in the soil environment. Therefore, in order to scientifically evaluate the ecological risk of heavy metals in soil, we need to take into account all kinds of heavy metals, accumulation degree, biotoxicity and bioavailability. Comprehensive evaluation results of the above methods, heavy metals Pb and As in the agriculture soil in the typical field areas in the Jianghan Plain are less polluted and have no influence on the surrounding environment. The accumulation of heavy metal Hg is not high, but it is a potential threat to the surrounding environment due to its high biotoxicity. Heavy metal Cd is the main pollution factor in the study area, which has a great impact on the surrounding environment. Therefore, it is urgent to take corresponding measures to reduce the risk of Cd pollution.
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