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

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.