填埋场环境下HDPE膜老化特性及其对周边地下水污染风险的影响

为研究危险废物填埋场环境下防渗系统HDPE膜（高密度聚乙烯膜）材料老化规律及其对渗滤液产生、渗漏和区域地下水环境的影响，通过HDPE膜缺陷现场检测及室内老化性能测试，获取了HDPE膜初始缺陷特征参数（漏洞密度）和缺陷演化特征参数（老化起始时间和半衰期），并以上述参数作为输入，综合运用HELP模型（填埋场水文过程评估模型）与Landsim模型（填埋场地下水污染风险模拟模型）对HDPE膜老化条件下的渗滤液产生、渗漏和地下水污染过程进行模拟预测.结果表明:①现场条件下HDPE膜在第2年开始老化，第8年达到半衰期.②HDPE膜老化导致漏洞数量和渗透系数增加，进而导致渗滤液渗漏量增加，地下水污染风险逐渐增加.短期（0~5 a）内，地下水超标概率为0，污染风险较小；中期（5~10 a）内，距离填埋场200 m内污染超标概率污染≥ 80%，污染风险较大，但400 m外的污染概率为0，污染风险较小；就长期（>10 a）而言，距离填埋场1 000 m处，污染超标概率达100%，地下水污染风险极大.填埋场现场条件下，防渗材料劣化及老化过程较实验室条件更为迅速，导致渗滤液长期渗漏、地下水污染风险加剧，因此建议加强填埋场设计和运行中HDPE膜抗老化研究，保障危险废物填埋场长期安全运行. 

Aging Behaviors of HDPE Geomembrane in Landfill Environment and Its Impact on Pollution Risk of Surrounding Groundwater

In order to research the aging regularity of HDPE membrane material and the influence of leachate generation, leakage and regional groundwater environment in hazardous landfill environment, the initial defect characteristic parameters (leak density) and defect evolution characteristic parameters (aging initiation time and half-life) of HDPE geomembrane were obtained through in-situ defect detection of HDPE geomembrane and indoor aging performance test of HDPE membrane. With the above parameters as input, the HELP model (landfill hydrological process assessment model) and the Landsim model (landfill groundwater pollution risk simulation model) were used to simulate and predict the leachate generation, leakage and groundwater pollution process under HDPE membrane aging conditions. The results showed that:(1) HDPE geomembrane began to age in the second year and reached half-life in the eighth year. (2) This led to the increase in the leakage and groundwater pollution risk increased gradually. In the short term (0-5 a), the risk of groundwater pollution is small (the probability of exceeding the standard is 0); In the medium term (5-10 a), the risk of groundwater pollution is high (the probability of exceeding the standard is more than 80%) within 200 m from the landfill, but the probability of pollution beyond 400 m is 0; in the long term (>10 a), the probability of pollution of up to 1000 m from the landfill is 100%, and the risk of groundwater pollution is serious. Finally, it should be pointed out that the deterioration and aging processes of the anti-seepage materials in the landfill are faster than that in laboratory conditions, which leads to the increase of groundwater pollution risk caused by long-term leachate leakage. It is suggested that the study on anti-aging measures of HDPE membrane in landfill design and operation should be strengthened to ensure the long-term safe operation of hazardous waste landfill sites.