填埋场渗漏风险评估的三级PRA模型及案例研究

在对填埋场渗滤液渗漏的环境风险进行系统分析的基础上,基于层次化风险评价,构建了填埋场渗漏风险评估的三级PRA模型,其中第1级概率风险评价模型(PRA)评价填埋场渗漏风险,第2级PRA评价地下水污染风险,第3级PRA评价人体健康风险.为定量研究不确定性因素对风险评价结果的影响,采用Monte Carlo方法研究三级PRA模型中参数的不确定性;采用事故树方法研究防渗层破损事故的不确定性.应用三级PRA模型评价了西南地区某危险废物填埋场渗滤液渗漏的环境风险,通过与实测数据和EPACMTP模型的比较,验证了该模型模拟结果的准确性. 第1级PRA评价结果显示,该填埋场渗漏量大于可接受渗漏量的概率为0.85,表明渗漏风险较大；第2级PRA评价结果指出,自第28年起渗滤液污染地下水的概率逐渐增大,在第47年污染概率等于1.00,主要污染物为Ni和Pb；第3级PRA评价结果表明,被污染的地下水将对填埋场周边居民构成健康危害,主要危害物为Pb,正常情况下其非致癌危害商为1.05；在不利条件下(降水量大、漏洞多、水文地质条件利于污染物扩散),非致癌危害商为1.34. 

3-Level of Probability Risk Assessment on Environmental Risk of Landfill Leakage and It's Case Study

Based on the theory of tiered risk assessment, a 3-tier probability risk assessment (PRA ) model was built to evaluate the environmental risk of landfill leachate leaking. The first level of PRA was used to predict the probability of leachate leakage, the second level was applied to calculate the risk of groundwater pollution, and the third level of PRA was implemented to assess the human health risk. To quantitatively research the uncertain elements and their influences on the risk assessment results, this study used the Monte Carlo method to propagate the randomness of input parameters, and applied Fault Tree Analysis method to quantify the uncertainties of liner damage. A hazardous waste (HW) landfill in the southwest of China was selected as the case area. The accuracy of the 3-tier model is verified by comparing the simulated results with the measured data and the results of widely used EPACMTP model. The results of the first level PRA indicated that the risk of leachate leaking was huge with the leakage probability greater than 0.85; the second level of PRA predicted that the leachate begin to pollute the groundwater after 28years, and the pollution risk reached to the maximal extent after 47years with the pollution probability equal to 1.00; the third level of PRA indicated that the contaminated groundwater will pose a non-carcinogenic hazard to surrounding residents. The main hazardous substance was lead with a non-carcinogenic hazard quotient of 1.34under unfavorable conditions, when rainfall was abundant, liner damage was serious and hydrogeological conditions were beneficial for the dispersal of pollutants, and of 1.05under normal conditions, respectively.