地下环境中水溶性污染物运动的模拟

Modeling of the Migration of Soluble Contaminants in the Subsurface of a Landfill Site

基于美国国家环保署(USEPA)开发的地下环境中微生物及化学物质传输模型FATMIC,对地下环境中可溶性污染物运动的数值模拟方法进行了研究。以位于某水库上游集水区的一个生活垃圾填埋场作为研究对象,选择横贯填埋场的一垂直剖面作为模拟区域,对填埋场区包括顶部粘土覆盖层、垃圾层、底部衬里及下部花岗岩基岩在内的地层进行了概化,并对其地层特征参数进行了量化,对填埋场衬里完好及破损两种条件下地下水流场和垃圾渗滤液可能对地下环境造成的影响进行了模拟。模拟结果表明,正常情况下,填埋场目前场底防渗层可以有效阻止垃圾渗滤液穿透;在防渗衬里发生破损后,垃圾渗滤液沿着裂缝渗入地下,25年内填埋场渗滤液的污染物前锋会随地下水流迁移至下游350 m处,对填埋场周边地下水将产生严重的污染,且随着时间的增加,污染愈加严重。可以认为2DFATMIC可以形象和准确地模拟填埋场衬里正常和破损条件下的地下水流场和渗滤液中可溶性污染物的时空分布。

The migration of soluble contaminants in the subsurface of a landfill site was modeled based on the FATMIC model developed by the U.S.Ministry of Environmental Protection.A landfill located at the water catchment area of a reservoir upstream was chosen as a case for the modeling study,and the vertical section of the landfill parallel to the groundwater flow direction as the modeling area.The landfilling area including clay cover,solid-waste body,liner,and the granite layer under the landfill was generalized,and the characteristic parameters of these layers were quantified.The groundwater flow field and the possible impact of the leachate on the subsurface environment were modeled and analyzed under the cases of the liner iu both good condition and poor condition.Results show that,in good condition,the single-layer liner system under the solid-waste body cau effectively prevent the leachate from penetrating the liner layer itself and polluting the groundwater.When the liner is damaged,the leachate will pass through the liner system and penetrate into the granite layer under the landfill,the forward of the leachate pollutant plume will move as far as 350 meters far away from the damaged site in 25 years,and the groundwater will be polluted by the leachate.The degree of contamination will also increase over time.It suggests that 2DFATMIC can perfectly model the flow field of the groundwater and the distribution of the soluble contaminant of the leachate in the subsurface under both good and poor liner conditions.