基于Visual Modflow的填埋场地下水污染迁移研究——以河北省保定市某飞灰填埋场为例

Research on Groundwater Pollution Migration in Landfill Site Based on Visual Modflow——Taking a fly ash landfill in Baoding City,Hebei Province as an example

垃圾焚烧发电和稳定化飞灰填埋场模式的联合处置方式是目前处理城市生活垃圾的有效手段之一,但填埋场对地下水存在潜在的污染风险,因此研究填埋场污染物迁移规律对于填埋场建设和管理具有重要的意义。以河北省保定市某飞灰填埋场为例,采用Visual MODFLOW建立了地下水水流模型和溶质迁移模型,对河北省保定地区某填埋场典型污染物泄漏情景下的污染物迁移扩散情况进行预测,并对渗滤液调节池短时泄漏和库区底部连续泄漏两种非正常状态下污染物的迁移特征进行分析。研究结果表明:渗滤液调节池短时泄漏情景下,泄漏30d后采取应急措施切断污染源,形成的污染晕向地下水下游运移,污染扩散距离及范围不断变大,但污染晕最大浓度在迁移过程中随着地下水的稀释不断减小。模拟期间超标范围未超过厂区边界,在此情境下,只要在泄漏发生后及时采取应急措施切断污染源,可以确保将污染晕控制在一定范围内,避免对厂区周围地下水环境产生明显不利影响。库区底部连续泄漏情景下,污染扩散距离及范围不断变大,如不加控制,会影响下游敏感目标。因此,为避免污染泄漏对下游及敏感点地下水环境产生不利影响,必须在泄漏发现后及时采取抽提或渗透反应墙等有效措施阻断污染物继续向下游运移,研究为填埋场地下水污染控制和环境影响评价提供管理和决策依据。

The combined disposal method of waste incineration power generation and stabilized fly ash landfill mode is currently one of the effective means to treat municipal solid waste.However,landfills have potential pollution risks to groundwater.Therefore,studying the law of pollutant migration in landfills is of great significance for the construction and management of the landfills.Taking a fly ash landfill in Baoding City,Hebei Province as an example,a groundwater flow model and a solute migration model were established using Visual MODFLOW to predict the migration and diffusion of pollutants under a typical pollutant leakage scenario in a landfill in Baoding,Hebei Province,and analyze the migration characteristics of pollutants under two abnormal conditions:short-term leakage in the leachate adjustment tank and continuous leakage at the bottom of the reservoir area.The research results showed that:under the short-term leakage scenario of the leachate adjustment tank,emergency measures are taken to cut off the pollution source after 30 days of leakage,and the pollution halo formed migrates to the downstream of the groundwater,and the diffusion distance and range of the pollution continuously increase,but the maximum concentration of the pollution halo decreases with the dilution of groundwater in the process of migration.During the simulation period,the exceeding range did not exceed the boundary of the plant area.In this scenario,as long as emergency measures are taken to cut off the pollution source in time after the leakage occurs,the pollution halo can be controlled within a certain range and avoid obvious adverse effects on the groundwater environment around the plant area.Under the continuous leakage scenario at the bottom of the reservoir area,the pollution diffusion distance and range will continue to increase.If it is not controlled,it will affect the downstream sensitive targets.Therefore,in order to avoid the adverse effects of pollution leakage on the groundwater environment of downstream and sensitive points,effective measures such as extraction or infiltration reaction walls must be taken in time after the leakage is discovered to block the continued migration of pollutants to the downstream.The study provides management and decision-making basis for groundwater pollution control and environmental impact assessment in landfill sites.