An integrated assessment model for heavy metal pollution in soil based on triangular fuzzy numbers and chemical speciation of heavy metal

The triangular fuzzy numbers theory was introduced to environmental assessment system.Double weighting system of heavy metal biology-toxicity was designed,which could characterize the biology-toxicity of different heavy metals and the biology-toxicity of different chemical speciation of every single heavy metal quantitatively.Afterwards,an integrated assessment model based on the index of geo-accumulation was built.As a model case,the soil pollution of heavy metal in Shizhuangding typical sewage irrigation area was selected to test and verify the integrated assessment model.The results showed that the integrated assessment value of the 5 heavy metals were markedly different,while their integrated pollution degree were in the order CdNiCuZnCr,and the Cd,Ni and Cu would be the primary pollution controlling factors in Shizhuangding typical sewage irrigation area.Compared with the result of the certain assessment model,it was concluded that the integrated assessment model overcame the shortcomings of the certain assessment model,by conveying information about both degree of heavy metal enrichment and potential biological risk of heavy metal pollution in soil more accurately which provided the basic theory to scientific decision-making.