基于随机-模糊耦合的污染场地健康风险评价及案例

A fuzzy-stochastic integrated model of contaminated site risk assessment model and case study

采用模糊理论描述风险评价过程的模糊不确定性,采用概率理论描述随机不确定性,同时为解决模糊数计算过程复杂的问题,将模糊变量表示成均匀随机变量的函数,用 Monte Carlo 算法模拟模糊变量之间的函数运算,从而实现模糊-随机方法的耦合.为验证该模糊-随机耦合模型的有用性,选取青海某汞化工污染场地进行案例研究,通过与 RBCA 模型比较,验证了该模型的基本精度,且能较好地表征场地参数的不确定性对风险评价结果的影响.案例分析的结果表明：人群主要暴露途径为经口摄入,贡献率为80%左右；正常暴露情形下,该场地的健康风险水平为0.28,风险水平可以接受,最不利情况下的健康风险风险水平为1.28,最不利情况出现的概率小于等于1%；该场地对人群的健康风险随着时间减小,在第6年左右其风险减小至可接受水平,建议无需对场地开展污染治理,只需在污染物高峰段（第1~6年或第6~8年）为居民提供替代水源以截断暴露途径,待场地污染水平自然衰减.

Risk assessment is associated with uncertainties in nature, and neglect of those uncertain elements in evaluating risk will inevitably lead to difficulty for decision-makers in the stage of risk management and decision-making. Fuzzy theory was used to describe the fuzzy uncertainties, and probability theory was employed to describe the random uncertainties. A coupled fuzzy-stochastic model was built to resolve the problem of complex computation of fuzzy numbers in which fuzzy number are represented with the function of uniform random variables. Monte Carlo method was also used to simulate the computation between fuzzy numbers. One mercury contaminated site located in Qinghai Province was selected as a case to demonstrate the effectiveness and reasonability of this coupled model. The reasonability of this model was verified by comparing simulated results of the widely used RBCA model. The case study indicated that：1） the main exposure pathway was oral intake with a contribution rate of 80%;2） the health risk of this contaminated site was acceptable with non-carcinogenic Hazard Quotient （HQ） of 0.28 under normal exposure condition;under the most unfavorable exposure condition which appearance probability was less than 1%, the health risk was unacceptable with HQ equals to 1.28;3） the health risk would decline in time and reach to an acceptable level after about six years. Therefore, it was suggested that the related responsibility should provide other drinking water resources to eliminate the exposure routine in the period of the first 6 years or the 6-8 years rather than take engineering measurements to remediate this contaminated site.