某典型污染场地地下水中氯代烃类的污染分布及迁移转化分析

Pollution distribution and migration law of chlorinated hydrocarbons in groundwater of a typical contaminated site

为探究氯代烃类在地下水中的污染分布和迁移转化规律,以天津某典型农药原料提纯场地为对象,通过地质勘察、监测采样与测试分析,对氯代烃类的水平和垂向分布特征及不同监测时间内的变化情况进行分析。结果表明,氯代烃类在研究区内水平分布不均,污染浓度较高的1,2-二氯乙烷和1,1-二氯乙烷主要集中在东侧办公室附近区域并随水流向四周扩散,点位检出率分别为66.67%和60.00%,点位超标率分别为40.00%和33.33%。污染物在垂向上不断向下运移,主要积聚在粉质黏土(4)_(2)、粉土(6)_(3)含水层中。在近一年的监测周期中,监测井Z17-2和Z9-2中氯代烃总浓度均呈现出先增加再降低的趋势,Z7-1中氯代烃总浓度呈现出逐渐升高的趋势,结合环境因子变化情况,表明该段时间内氯代烃浓度变化主要受到污染源和自然衰减两个因素影响,污染物浓度越高,自然衰减速率越慢。

In order to explore the pollution distribution and migration and transformation of chlorinated hydrocarbons(CAHs)in groundwater,taking a typical pesticide raw material purification site in Tianjin as the object,the horizontal and vertical distribution characteristics of CAHs and the changes in different monitoring time were analyzed by geological survey,monitoring sampling and test analysis.The results showed that the horizontal distribution of CAHs in the study area was uneven.1,2-dichloroethane and 1,1-dichloroethane with high pollution concentrations were mainly concentrated in the area near the east office and diffused around with the flow.The detection rates of point positions were 66.67%and 60.00%,and the exceeding rates of point positions were 40.00%and 33.33%.Pollutants move downwards in the vertical direction,mainly accumulated in silty clay(4)_(2)and silty soil(6)_(3).In the monitoring cycle of nearly one year,the total concentration of CAHs in monitoring wells Z17-2 and Z9-2 showed a trend of first increase and then decrease,and the total concentration of CAHs in Z7-1 showed a trend of gradual increase.Combined with the change of environmental factors,it showed that the change of CAHs content in this period was mainly affected by pollution sources and natural attenuation.The higher the pollutant content,the slower the natural decay rate.