西南某退役化工厂场地地下水污染特征及污染物迁移规律分析

Analysis of groundwater pollution characteristics and pollutant migration law of a decommissioned chemical plant site in Southwest China

针对某退役化工厂场地受有机物污染的地下水含水层,开展地下水污染特征调查,通过风险评价模型、DRASTIC模型分别对研究区进行人体健康风险及地下水脆弱性评价,构建污染物地下水迁移扩散模型,进一步剖析典型污染物迁移扩散的影响因素及动力学模式。结果表明:研究区地下水受1,2-二氯乙烷、苯、三氯甲烷的污染,1,2-二氯乙烷的总致癌风险为4.00×10^(−6),超过人体健康风险可接受水平,主要暴露途径为吸入室内空气中来自地下水的气态污染物;研究区地下水脆弱性指数为4.912~5.305,整体处于中等脆弱性水平,地下水系统抵御污染能力较强,地下水埋深、净补给量和含水层厚度是影响地下水脆弱性的主要因素;1,2-二氯乙烷迁移扩散受地下水对流作用、含水介质吸附阻滞作用、生物化学作用共同影响,地下水对流作用是其迁移扩散的主要动力,含水介质吸附阻滞作用及生物化学作用对于其分布范围影响显著。

Taking a decommissioned chemical site as the research object,in view of the organically polluted groundwater aquifer in it,the groundwater pollution characteristics were investigated.The risk assessment model and DRASTIC model were applied to evaluate the human health risk and groundwater vulnerability in the study area,respectively,and the groundwater migration and diffusion model of typical pollutants was constructed to further analyze the influencing factors and dynamic modes of the migration and diffusion of typical pollutants.The results showed that the groundwater in the study area was polluted by 1,2-dichloroethane,benzene and trichloromethane.The total carcinogenic risk of 1,2-dichloroethane was 4.00×10^(−6),exceeding the acceptable level of human health risk,which was mainly caused by inhaling gaseous pollutants from groundwater in indoor air.The groundwater vulnerability index of the study area ranged from 4.912 to 5.305,which was at the medium vulnerability level as a whole.The groundwater system had a strong ability to resist pollution.The groundwater depth,net recharge and aquifer thickness were the main factors affecting groundwater vulnerability.The migration and diffusion of 1,2-dichloroethane were jointly affected by the convection of groundwater,the adsorption and retardation of aqueous media,and biochemical effects.Groundwater convection was the main driving force for its migration and diffusion.Moreover,the adsorption and retardation of aqueous media and biochemical effects had significant effects on the distribution range of 1,2-dichloroethane.