垃圾填埋场渗滤液变密度地下水溶质运移模拟

Simulation of Solute Transport in Variable-Density Groundwater for Landfill Leachate

为分析垃圾填埋场变密度渗滤液对地下水的影响,本文通过MODFLOW中的SEAWAT模块建立变密度地下水溶质运移模型,模拟了在密度效应情况下垃圾渗滤液在地下水中的运移规律,并且与不考虑密度影响的模型结果进行了对比。结果表明,在密度驱动下污染物运移得更快,出现了明显的“指流”,在3650 d时,变密度模型中地下水质量浓度大于10%源强浓度的面积比恒定密度模型结果多1611.95 m~2;这表明变密度模型计算的污染物影响范围要比恒定密度模型的范围要大。根据不同质量浓度源强模拟结果可以看出,在整个预测期内源强为90 g/L的影响面积最大,随着源强浓度降低,影响面积逐渐减小。根据观测孔浓度曲线可以看出,1号、2号和3号孔的10 m、2 m观测层位浓度历时曲线都呈现变密度模型结果高于恒定密度模型,且底部观测层位更容易捕捉到污染物。因此在分析垃圾渗滤液或者其他密度较高的污染物对地下水的影响时,应重视密度因素。

In this study,a variable density groundwater solute transport model was established by SEAWAT module(from MODFLW)to simulate the migration of landfill leachate in groundwater under density effects.The results show that the pollutants migrate faster under the driving of density,forming a clear“finger flow”phenomenon.At 3650 d,the area where the groundwater concentration is greater than 10%of leachate concentration in the variable density model is 1611.95 m~2 more than that of the constant density model,indicating that the scope of contaminant plume calculated by the variable density model is larger than that of the constant density model.According to the simulation results of different concentrations of leachate,the largest scope of contaminant plume occurs in the scenario with the highest concentration of leachate(90 g/L),and it decreases with the concentration of leachate decreases.From the time series curves of concentration at 10 m and 2 m in monitoring well 1,2 and 3,the results of the variable density model are higher than those of the constant density,indicating that the density is an important factor that cannot be ignored when analyzing the impact of landfill leachate or other higher density contaminants on groundwater.