滨海平原区某生活垃圾填埋场地下水污染修复模拟

渗滤液是垃圾填埋场区地下水的主要污染源。以滨海平原区某生活垃圾填埋场为例，采用MODFLOW/MT3D建立模型进行污染物的迁移模拟和修复模拟，模拟持续污染和清理污染源并配套抽水井的2种工况下，COD_Mn在浅层地下水中的迁移扩散特征。模拟结果表明：由于滨海平原区浅层地下水含水层渗透系数很小，水动力条件差，污染物主要影响埋深10 m以浅的2个含水层；持续泄漏将造成污染羽中污染物含量很高，但污染物向场外迁移扩散的距离却很有限，20年后污染物超出场界的迁移距离不超过70 m;设置抽水井可有效地清理污染物，但污染羽的清除速度很慢，需要5～10年的连续抽水方可使污染羽收缩至场内。实际修复中，可根据修复进展情况实时调整抽水井的运行和布设，关停已修复好区域的抽水井，同时加大污染中心抽水井的出水量，并在修复多年污染物浓度依然较高的地段增布抽水井，以加快污染修复速度。建立的污染物迁移和修复模拟模型可为其他相关垃圾填埋场地下水环境调查评估和污染治理提供参考与借鉴。

SIMULATION OF RESTORATION OF GROUNDWATER POLLUTION IN A LANDFILL IN COASTAL PLAIN AREA

Leachate is the main pollution source for groundwater in landfill areas. In this paper, a landfill in a coastal plain area was studied. The migration and remediation of pollutants in groundwater were simulated based on MODFLOW/MT3D modules. The studied working conditions included continuous pollution, cleaned pollution sources and supported pumping wells, and then we simulated the migration and diffusion characteristics of permanganate index in shallow groundwater. The simulation results showed that because of the very small permeability coefficient and the poor hydrodynamic conditions of shallow groundwater aquifers in the coastal plain area, the pollutants mainly affected two aquifers with a depth of less than 10 m; continuous leakage would result in a high content of pollutants in the groundwater plume, but the migration and diffusion distance of pollutants outside the site would be very limited, and after 20 years, the migration distance of pollutants beyond the site boundary would be less than 70 m; setting pumping wells can clean up pollutants effectively, but the groundwater plume removal speed would be very slow, and it would take 5 to 10 years of continuous pumping to shrink the groundwater plume into the site boundary. In the actual repair, the operation and layout of pumping wells can be adjusted according to the repair progress, the pumping wells in the repaired area can be closed, the water yield in the pollution centre can be increased, and pumping wells can be added in the sections with high pollutant concentration to speed up the pollution repair. The simulation model of pollutant transport and remediation established in this study can be used as a reference for the investigation and assessment of the groundwater environment and pollution control in other similar landfill sites.