潮汐作用对滨海垃圾填埋场地下水污染物迁移影响模拟研究

Simulation of tidal effects on migration of groundwater pollutant in coastal landfill

潮汐过程对滨海地区垃圾填埋场污染物的迁移影响显著.为探究潮汐作用下垃圾填埋场地下水污染物迁移过程,以深圳市某滨海垃圾填埋场为例,构建该场地地下水溶质运移数值模型,分析潮汐作用造成的地下水位周期性波动条件下特征污染物在含水层中不同时期的污染范围及浓度变化规律.结果表明:近海岸地下水位受潮汐作用明显,水位波动主要受含水层水文地质参数和潮水位变幅影响,污染物峰值浓度大幅降低,在含水层中滞留时间明显增加.该垃圾填埋场中特征污染物的污染范围和浓度呈现出丰大枯小的周期性变化特征,其中丰水期末最大污染范围和浓度分别为47547 m^(2)、21.54 mg·L^(-1),枯水期末最大污染范围和浓度分别为25605 m^(2)、12.73 mg·L^(-1).污染物峰值浓度最大降幅37%,滞留时间最长增加43 d.近海岸地下水污染物穿透曲线呈现日周期性波动,随着远离地表水边界,这种周期性波动越不明显,距地表水边界20 m时,污染物穿透曲线无明显日内周期性波动.研究结果可为滨海垃圾填埋场地下水监测方案的制定和地下水污染治理提供理论依据和参考.

The tidal process significantly impacts the migration of contaminants generated from the landfills in the coastal area.To investigate the migration of contaminants,simulations of solute transport were performed based on the data from a coastal landfill in Shenzhen City.The temporal and spatial distributions of pollutants associated with the periodic fluctuation caused by tidal action were analyzed.The results show that near the coast the groundwater level is significantly affected by the tide,which is caused by the hydrogeological parameters and the amplitude of the tidal level.The peak concentration of contaminant dramatically decreased,and the residence time of contaminant in the aquifer significantly increased.The contamination range and concentration of the characteristic contaminant in the landfill vary periodically with wet season and dry season.The maximum pollution range and concentration are 47547 m^(2),21.54 mg·L^(-1) at the end of wet season,and 25605 m^(2),12.73 mg·L^(-1) in the dry season,respectively.The maximum pollutant concentration decreased by 37%,and the maximum residence time reached 43 days.The breakthrough curve of contaminant near the coast shows a daily periodic fluctuation which becomes weak with the distance from the surface water boundary.No obvious daily periodic fluctuation of contaminant could be observed when the distance from the surface water increased to 20 m.The results of this study are expected to provide a theoretical basis and reference for planning the groundwater monitoring and controlling the groundwater contaminant in the coastal landfill.