上海浦东浅层地下水环境三氯乙烷自然衰减规律及过程模拟

Natural Attenuation Simulation of 1,1,1-Trichloroethane in Shallow Groundwater at a Contaminated Site in Pudong,Shanghai

针对某三氯乙烷（1,1,1-Trichloroethane）污染场地,采用地下水污染调查和地下水污染迁移转化模型,描述了污染场地自然衰减的潜在能力。通过对污染地下水样品的采集和测定,发现氯代烃污染物主要存在于地下2~6m的地层中,被污染的区域面积约1 000m2,并且场地含水层中发生了自然衰减过程。地下水模型的模拟结果表明地下水流场较为稳定且水力梯度较小,联合吸附作用共同导致了污染物的缓慢迁移扩散。考虑到吸附作用和生物降解作用,利用等温吸附实验和自然衰减模拟实验,计算和优选了三氯乙烷在含水层土壤中分配系数为0.06m3/kg和准一级降解动力学参数为0.005d-1。利用Visual MODFLOW软件模拟,预测污染区域的高质量浓度三氯乙烷的衰减,且5年后三氯乙烷的最高质量浓度低于300μg/L的荷兰标准值。

Chlorinated hydrocarbon pollution of groundwater environment has become a worldwide environmental pollution problem. 1,1,1-tricbloroetbane （TCA） in groundwater is susceptible to a variety of natural degradation mechanisms. Natural attenuation at a 1,1,1-trichloroethane （TCA）-contaminated site was investigated using reactive transport model to characterize its potential effectiveness. The results of the sampling and detection indicated that the majority of the contaminant mass was present at 2--6 m in depth, the contaminated area was about 1 000 m2 , and natural attenuation processes were occurring at the site. The MODFLOW groundwater model indicated that groundwater was stable and its hydraulic slope was low, which, along with the adsorption factor, slowed contaminant diffusion. Using the adsorption isothermal experiment and the column experiments of the simulation of natural attenuation of TCA in the aquifer, the kinetic parameter of adsorption was 0. 06 m3/kg and the kinetic constant for biotic dehydrochlorination of TCA was 0. 005 d 1. The contaminated area was predicted to be diminished gradually, and the maximum concentration of TCA to fall below the standard of 300μg/L in about 5 years. The simulation is of great significance for the groundwater pollution mechanism and the controlling technique of pollutants.