基于数值模拟的某污染区地下水风险管控值确定

针对地下水风险管控目标值确定较难的问题，以某废弃铁合金厂为研究对象，讨论地下水中Cr （Ⅵ）污染对下游敏感目标河流的环境影响，采用数值模拟方法，确定水力截获条件下该污染区地下水风险管控目标值。结果表明:天然条件下，2500 d后，Cr （Ⅵ）浓度>0.5 mg/L的污染羽将迁移至河流处；在水力截获条件下，当水力截获Cr （Ⅵ）浓度为10 mg/L以上的污染羽范围时，排泄至河流处Cr （Ⅵ）最高浓度为0.46 mg/L，可达到地下水风险管控的目的。最终确定本场地地下水风险管控值为10 mg/L，使地下水风险管控的面积减少了约9.45万m2，节约了污水处理的成本。该成果可为地下水风险管控目标值的确定提供方法支撑，为我国污染地块地下水修复方案编制提供设计支撑。

DETERMINATION OF GROUNDWATER RISK CONTROL VALUE OF A POLLUTED LAND BASED ON NUMERICAL SIMULATION

Aiming at the difficult problems of determining the target value of groundwater risk management and control, this article took an abandoned ferroalloy plant as the research object, and discussed the environmental impact of hexavalent chromium pollution in groundwater on the downstream sensitive target rivers. Numerical simulation methods were used to determine the pollution under hydraulic interception conditions, the target value of groundwater risk management and control of the plot. The results showed that:under natural conditions, after 2500 days, the pollution plume with hexavalent chromium concentration greater than 0.5 mg/L will migrate to the river; under hydraulic interception condition, when the hydraulic interception of the hexavalent chromium concentration was above 10 mg/L of the pollution plume, the highest concentration of hexavalent chromium discharged to the river was 0.46 mg/L, achieving the purpose of groundwater risk management and control. It's finally determined that the groundwater risk control value of this site was 10 mg/L, which reduced the area of groundwater risk control by about 9.45 m2 and saved the cost of sewage treatment. This study provides support for determining the target value of groundwater risk management and control, and preparation of groundwater remediation plans for contaminated land in China.