填埋场长期渗漏的环境风险评价方法与案例研究

填埋场的长期渗漏是由于防渗膜老化、导排层淤堵等原因,导致填埋场封场后渗滤液渗漏量增加的现象. 为分析渗滤液长期渗漏对填埋场环境风险的影响,采用Landsim-HELP耦合模型进行渗漏源强计算和污染组分迁移转化计算. 在此基础上,以致癌风险和非致癌风险为渗滤液渗漏的环境风险表征,采用剂量-效应模型对风险值进行计算. 最终构建了基于Landsim-HELP耦合的填埋场长期渗漏的环境风险评价模型,并将其用于山西省某工业固体废物填埋场渗漏风险研究. 结果表明:①短期(0~100 a)内,在CLTP(考虑长期性能衰减)和NCLTP(不考虑长期性能衰减)情景下,渗滤液渗漏的环境风险无明显差异, 并且二者的风险值均低于可接受风险水平；而长期(>100~1 000 a)状态下,2种情景的风险值差别较大,其中CLTP情景下的风险为NCLTP情景下的7倍左右,并且主要体现为Cr(Ⅵ)的致癌风险(10-4). 采用Monte Carlo方法分析风险结果的不确定性,其中Cr(Ⅵ)致癌风险值的不确定性为6.7,Cr(Ⅵ)和TCr的非致癌风险评价结果的不确定性分别为2.3、2.1. 

Method and Case Study to Evaluate Long-Term Environmental Risks from Landfill Leakage

Abstract:Long-term leakage of leachate from landfills refers to the obvious increase in the leakage rate after landfill closure due to performance degradation of the linear system and clogging of the drainage system. To consider the influence of this leakage on the risk assessment results, the Landsim model, which accounts for the degradation process of capping system, linear system and drainage system, was coupled with the HELP model to calculate the long-term leakage and the transport of contaminants in vandose and aquifer. Cancer risk and hazard quotient were used to characterize the environmental risks of long-term leaking, and were calculated by the Dose-Effect model. As a result, a coupled HELP-Landsim-Dose-Effect (HLDE) model was constructed to assess the long-term risk of landfill leakage with the consideration of its performance degradation. The coupled model was then applied to the long-term risk assessment of an industrial solid waste landfill in Shanxi Province, according to the procedures recommended by the Technical Guidelines for Environmental Risk Assessment on Projects. The case study results indicated that there was not an obvious difference between the risk results of CLTP (consideration long term performance) and NCLTP (no consideration of long term performance) over a short period (0-100 a). However, over long periods (>100-1000 a), significant differences existed:risk over the long term under the scenario of NCLTP was relatively small and could be accepted; however, risk under the scenario of CLTP over the long term, whose main source was from the carcinogenic effect of Cr(Ⅵ) and whose magnitude was as high as 10-4, could not be accepted. In addition, uncertainty analysis indicated that due to the influence of model parameters, there was a big uncertainty in the risk result. The uncertainty coefficient of Cr(Ⅵ)'s carcinogenic risk was 6.7, while the uncertainty coefficients of Cr(Ⅵ) and TCr's non-carcinogenic risk were 2.3 and 2.1, respectively.