某垃圾填埋场氯化物运移的不确定性分析

Uncertainty analysis of chloride transport in groundwater of a landfill

实际污染物的运移浓度和污染范围受水文地质参数的数值不确定性和空间分布随机性的影响,常规数值模型不能有效地模拟污染物运移。分别将水文地质参数的数值不确定性和空间分布随机性考虑到常规数值模型中,以某垃圾填埋场氯化物渗滤液运移为例,计算了该垃圾填埋场1940-2000年60 a氯化物的运移浓度和运移范围变化情况。以第43年计算结果为例,结果表明:考虑了不确定性因素的随机模型多次模拟结果平均值与实际值吻合更好,说明随机模拟法较常规数值模拟更具有优势;当自变量变化范围为20%时,考虑数值不确定性的随机模型计算结果比同等条件下考虑空间随机性模型计算结果的平均偏差值和平均方差值大25.04%和26.95%;60 a内氯化物浓度和污染范围的计算结果不确定性大小存在变化,两种不确定性模型计算得到的结果大小变化趋势一致,即呈现出先增大后减少的趋势。通过不确定性分析可以掌握该地区氯化物浓度的变化范围,在划分不同浓度置信区间的基础上进行风险分析,为地下水的污染防治提供数据参考。

The actual pollutant transport concentration and pollution range are affected by the numerical uncertainty and random spatial distribution of hydrogeological parameters.Conventional numerical models cannot effectively simulate the transport of pollutants.So,we integrated the numerical uncertainty and random spatial distribution of hydrogeological parameters into the conventional numerical model respectively for better simulation results.Taking the chloride leachate transport of a landfill as an example,the variation of its concentration and range from 1940-2000 year is calculated.Taking the results of year 43 as example,the results show that the mean values of multiple simulations of the random models which takes into account the uncertainty factors were consistent with the actual values,indicating that the proposed models are superior to conventional numerical models.It is concluded that when the variation range of the independent variables was 20%,the mean value and mean variance values of numerical uncertainty random model were 25.04%and 26.95%larger than those of the random spatial distribution model.The uncertainty of calculation results of chloride concentration and pollution range varied in the study period,and the variation trend of the uncertainty of calculation results of two kinds of uncertainty models were consistent which increased first then decreased.Through uncertainty analysis,the variation range of chloride concentration in this area are clarified,the risk analysis can be carried out on the basis of dividing different concentration confidence intervals,so as to provide data reference for the prevention and control of groundwater pollution.