Study On Risk Assessment Method Of Heavy Metal Contaminated Site Based On Speciation Evolution

The study of heavy metal speciation in soil is of great significance for risk assessment of soil contaminated sites.The chemical sequential.extraction method is an important method to study the metal fractions in soil and sediments.In this study,four extraction methods,namely BCR,Wenzel,Ciemat,and Shiowatana,were used to comprehensively compare the arsenic extraction effects.The experimental results showed that the Shiowatana extraction method had better extraction recovery and experimental reproducibility,and the average recovery and coefficient of variation were 96.87%and 3.63%,respectively.Besides,this Shiowatana extraction method has obvious advantages for the extraction and quantitative analysis of bioavailable arsenic.Therefore,this extraction method is a reliable extraction method for arsenic.In this study,a realgar mining area was selected as the research object,and the Shiowatana sequential extraction method was selected as the research tool for the arsenic extraction.Through the non-linear fitting of data,a Delayed Geochemical Hazard model of arsenic contaminated sites was established to assess the risk of dynamic chemical disasters in the realgar mining area.The experimental results show that there are 4.76%to 7.14%of the regions in the mining area with the risk of an outbreak of geochemical disasters.In this paper,a lead and cadmium compound contaminated site was selected as the research object,and the Tessier extraction method was used to extract and analyze the lead and cadmium fractions in the region.Then,the Delayed Geochemical Hazard model and the Hakanson potential ecological risk index method were combined to establish a DGH model for the compound contaminated site.The final results show that 30%to 70%of the compound contaminated site is at the risk of chemical disasters.Although the experiment finally achieved a risk assessment for compound contaminated sites through the establishment of a Delayed.Geochemical Hazard model,the DGH model was not perfect enough.The compound model misses a large number of potential chemical disasters outbreak pathways of heavy metals.Therefore,the application of the Delayed Geochemical Hazard model in compound contaminated sites still faces many problems and new trials are needed.