基于保护水环境的场地地下水风险评估模拟应用研究

Modelling Application for Contaminated Land Groundwater Risk Assessment Based on Prospection of Water Environment

以江苏省某溶剂化工场地为例,利用英国污染地块水文地质风险评估模型研究了该场地地下水污染物对场地内及周边水环境的影响。比较了稳态和非稳态地下水溶质迁移模型(Ogata Banks、Domenico、Time variant Domenico)对污染物在自然衰减条件下从污染源向场地边界迁移过程模拟。结果表明:该场地的地下水中苯、乙苯、氯苯、1,2-二氯苯、1,4-二氯苯、氯仿超过了地下水质量Ⅲ类标准,但场地内污染物对场地边界地下水的潜在环境风险基本可以忽略。Ogata Banks与Domenico模型对于污染物在含水层的自然衰减下的迁移模拟表明污染物在30 m内的迁移过程中浓度下降较快,在30 m外的迁移过程中污染物的浓度较低且衰减不明显。Domenico模型计算较为简洁,在风险评估中具有较强的适用性;敏感性分析表明合规点至污染源距离x、含水层容重ρ、含水层孔隙度n、有机碳含量f_(oc)、有机碳分配系数K_(oc)、水力传导系数K、水力梯度i均影响污染物在含水层的自然衰减迁移过程,通过精细化水文地质调查获取上述参数将有助于提高风险评估结果的精确度。

Taking a solvent contaminated site in Jiangsu Province as a case study,the impact of groundwater contamination on the surrounding groundwater was studied by using hydrogeological risk assessment model for land contamination in the UK.The contaminants migration process from source to site boundary can be simulated under the conditions of natural attenuation.The simulation results of the groundwater solute transport using Ogata Banks,Steady-state Domenico and Time variant Domenico models were compared.The results showed that the concentrations of benzene,ethylbenzene,chlorobenzene,1,2-dichlorobenzene,1,4-dichlorobenzene,and chloroform exceeded the Ⅲ grade of the groundwater quality standard,but the groundwater surrounding the site has negligible environmental risk.The Ogata Banks and Domenico models'simulation of the migration of contaminants under the natural attenuation of the aquifer showed that the concentration of contaminants decreased rapidly during the migration process within 30 m,and the concentration of pollutants was low and the attenuation was not obvious during the migration process outside 30 m.The Domenico model is relatively simple and advantageous in the application of risk assessment.Sensitivity analysis showed that the hydrogeological parameters,such as migration distance(x),aquifer bulk density(ρ),aquifer porosity(n),organic carbon content(f_(oc)),organic carbon distribution coefficient(K_(oc)),hydraulic conductivity(K),and hydraulic gradient(i),could affect the natural attenuation migration process of contaminants in the aquifer,thus to improve the accuracy of risk assessment results,the abovementioned parameters need to be obtained through refined hydrogeological investigation.