| In recent years,the mass production and use of persistent organic pollutants(POPs)on a large scale in the world has continued to grow and become a hotspot.Polycyclic Aromatic Hydrocarbons(PAHs)Potential toxicity,carcinogenicity and mutagenicity,and can be long-distance migration,easy to adsorb on the sediment,its risk assessment has important practical significance.The existing research results focus on the threshold method,the organic carbon homogenization method,the average effect of the median commercial law,and so on,and the ecological risk of polycyclic aromatic hydrocarbons in the whole sediments has no systematic evaluation method.In this paper,we consider the comprehensive risk of polycyclic aromatic hydrocarbons(PAHs)based on the environmental quality standards of Canadian sediments.The ecological risk is divided into five grades:I(rare effect level,REL,negligible risk),Ⅱ(threshold effect level,TEL,fewer risk),III(occasional effect level,OEL,acceptable risk),IV(probably effect level,PEL,higher risk),V(frequent effect level,FEL,great risk),using set-pair analysis theory to build the basic model.According to the complexity and ambiguity of ecological risk assessment,the weight of each index was determined by AHP and the toxicity equivalent factor(the benzo[a]anthracite was the most toxic,and the weight of the total ecological risk assessment was the largest,Benzo[a]pyrene,and more than naphthalene,acenaphthene,acenaphthene,fluorine,fluorine,phenanthrene and other weight greater).Then the model uses the triangular fuzzy number to improve the difference coefficient,calculates the comprehensive number of links and the level of eigenvalues,selects the measured and published polycyclic aromatic hydrocarbons(PAHs)data in the sediments to carry out the ecological risk assessment,which avoids the homogenization conclusion which is limited to the low risk and the potential risk of the monomer,and complements the original conclusion.The results show that:(1)The S-T model provides a simple,objective,and effective method for the grading assessment of PAHs in sediments.The S-T model is based on set pair analysis and triangular fuzzy numbers.It takes into account the interaction factors between compounds and does fuzzy processing,and improves the coefficient of difference,reflecting the inter-grade ambiguity.The calculation process is simple and the results are intuitive,which has similar results with present evaluation methods and can be used as supplements.(2)The S-T model conclusion has a global view when there are more data and the result is more objective and accurate.The S-T model synthesizes the toxicity of various contaminant monomers and takes into account the ambiguity of their interaction.The weights are determined by their toxicity equivalent factors.Monomers with large toxicity have a large weight,and the uncertainty of toxicity is treated by triangular fuzzy numbers.The conclusions are more accurate with the more data.(3)The S-T model is more practical when comparing regional risks.The S-T model evaluation results show that the ecological risk of PAHs in the surface sediments in the surrounding area of the Meiliang Bay area and the Beibu Gulf oilfields is gradeⅢ.The PAHs surrounding Taihu Lake,Fuzhou River,Chaohu Lake,and Shenzhen coastal waters The risk is grade Ⅱ.The ecological risk of PAHs in the surface sediments of the entire Taihu Lake basin(including drinking water sources),Qiandao Lake,Sansha Bay,the Yangtze River estuary,and Zhejiang coastal waters is Grade I,and the results are more intuitive and practical when compared across regions. |
