非正规填埋场渗漏的层次化环境风险评价模型及案例研究

A tiered model to evaluate the environment risk of leachate leakage in irregular waste landfill and a case study

通过系统分析非正规填埋场建设、运行和封场的工艺工程及其环境特征,将其渗漏风险的发生过程划分为3个阶段,针对不同阶段采用不同风险评价模型:采用水均衡模型和Monte Carlo方法研究渗滤液的渗漏风险;采用基于Darcy定律和Fick定律的溶质运移方程和Monte Carlo方法研究地下水的污染风险;采用剂量-效应模型评价受渗滤液污染地下水的人体健康风险,最终构建了非正规填埋场渗漏风险评价的层次化风险评价模型.应用该模型评价了西北地区某非正规填埋场的环境风险.结果表明:1第1层次的风险评估结果能较好的表征第2层次和第3层次风险的大小,其结果可作为是否进行后续风险评价的判断依据;2仅就本填埋场而言,若采用层次化风险评价模型,可大幅节约风险评价所需的时间成本(95%)和工程成本(96.5%);3案例表明该填埋场渗漏量超过可接受渗漏量的概率为0,渗漏风险极小;渗滤液的渗漏对地下水影响很小,污染风险为0;该填埋场渗滤液中存在的六价铬和总铬的非致癌危害商均低于10-2,健康风险水平很小;综合考虑,该填埋场的环境风险较小,无需采取工程措施对其进行治理或搬迁.

Through systematic analysis on the construction,operation and closure stages of irregular solid waste landfill( ISWL) and its environmental characteristics,the risk of leachate leakage is divided into three stages. Different models are used to evaluate the risk in different stages. Water balance model and Monte Carlo method are used in the first stage to calculate the leachate leakage risk,solute transport equation based on Darcy’ s law,Fick’ s law,and the Monte Carlo method is used in the second stage to evaluate the groundwater contamination risk,and Dose-effect model is used in the third stage to assess the health risk of contaminated groundwater by leachate contamination. An ISWL in the southwest China is selected as a case study to evaluate the human risk of leachate leakage using tiered model. The results show that: 1 the risk assessment in the first stage can better characterize the risk-in the second and third stages,therefore can be used to determine whether subsequent assessments should be taken; 2 as far as this case is concerned,the hierarchical model can significantly save the time and cost of risk assessment by 95% and 96. 5%,respectively; and 3 its leakagerisk is acceptable with the probability that its leaking rate is large than the acceptable rate equal to zero; the leakage of leachate in this landfill produce little impact on the groundwater with the pollution risk equal to zero; the health risk of population is extremely small and acceptable with the non-carcinogenic hazard quotient of Cr(VI) and Total(Cr) smaller than 10- 2,which means that there is no need to take measures for its treatment or relocation.