Comprehensive assessment method of site heavy metal pollution risk based on fuzzy mathematics

Based on the theory of traditional soil evaluation methods and the framework of fuzzy mathematics, this paper established an evaluation model composed of risk factor set, risk evaluation set, membership function, evaluation matrix and weight coefficient, and finally formed a set of comprehensive evaluation methods for heavy metal pollution risk of sites. The polluted soil of a smelter from Tongling, Anhui was selected as the research site to analyze the pollution of heavy metals and verify the effectiveness of the evaluation model. The average contents of heavy metals in the surface soil of the study site were 1382mg/kg for As, 64.9mg/kg for Cd, 4973mg/kg for Cu, and 3403mg/kg for Pb. Among them As and Pb were seriously polluted. Compared to the traditional soil evaluation method, the integrated evaluation method considered three aspects especially human health risk, groundwater migration risk and ecological risk of heavy metals. The proportion of area occupied by different risks after interpolation was safe (25.3%), low risk (5.86%), medium risk (9.00%) and high risk (59.9%). Compared with nemero index method, the area of high risk in the comprehensive evaluation method decreased by 9.50%, while the area of medium risk, low risk and safe area increased by about 3.54%, 3.83% and 1.20% respectively, indicating that the overall risk decreased. Compared with traditional soil evaluation methods, the comprehensive evaluation method based on fuzzy mathematical model is not limited to a single index of total heavy metals, but carries out a more detailed pollution risk assessment regarding the actual situation of the site and the way of land reuse, which highlights the contribution of different heavy metal pollution and thus providing more accurate risk assessment of soil pollution. © 2023 Chinese Society for Environmental Sciences. All rights reserved.