灰渣填埋场地下水中典型污染物迁移数值模拟

Numerical simulation of typical pollutants transfer in groundwater of ash and slag landfill

地下水中重金属污染具有隐蔽、不可逆等特点,危害较大。固体废物填埋场一旦发生渗漏,渗滤液中各种重金属等污染物就会对当地地下水产生污染风险。以义马煤业综能新能源有限责任公司灰渣填埋场为例,通过分析其水文地质条件,建立水文地质概念模型,选取COD、氟化物、锌、镉、铅、六价铬、砷作为预测因子,采用Visual MODFLOW软件定量计算和预测重金属污染物在地下水中的迁移转化过程。结果表明:当填埋场底部污染物以及渗滤液调节池出现渗漏事故时,均会对下游产生不同程度的污染和影响;在填埋场底部渗滤液渗漏1000 d后,3种污染物浓度出现超标,7300 d后,除砷离子外,其他预测因子浓度均超过检出值,即对地下水存在影响;在渗滤液调节池出现渗漏1000 d后,COD、铅和六价铬浓度在部分地区超过检出值,但所有预测因子未发现超标,7300 d后所有预测因子未发现影响区和超标区;整个模拟过程中迁移速度最快的污染物为铅,影响范围最大的污染物为COD。研究结果可为评价该填埋场对当地地下水环境的影响提供参考。

Heavy metal pollution in groundwater has the characteristics of concealment and irreversibility,which is more harmful.Once the solid waste landfill site leaks,various heavy metals and other pollutants in the leachate will cause pollution risks to local groundwater.Taking the ash and slag landfill of Yima Coal Industry Comprehensive Energy New Energy Co.,Ltd.as an example,a hydrogeological conceptual model was established by analyzing its hydrogeological conditions.COD,fluoride,zinc,cadmium,lead,hexavalent chromium and arsenic were selected as predictors,and the migration and transformation process of heavy metal pollutants in groundwater was quantitatively simulated and predicted by using Visual MODFLOW software.The results showed that when the pollutants at the bottom of the landfill and the leachate regulating tank leak,it would cause different degrees of pollution and impact on the downstream area.The concentration of three pollutants exceeded the standard after 1000 days of leakage from the bottom of the landfill,and after 7300 days,the concentration of other predictors still could be tested out except arsenic ions,that is,it had an impact on groundwater.For leakage from the leachate regulating tank,the concentration of COD,lead and hexavalent chromium could be tested out in some areas after 1000 days,but none of the predictors exceed the standard,and all the indices did not generate influential area and the stander-exceed area after 7300 days.The fastest moving pollutant in the whole simulation process was lead,and the pollutant with the largest influence was COD.The research results can provide reference for impact assessment of landfills on local groundwater environment.