某水源地地下水四氯化碳污染特征分析

Characteristics of Carbon Tetrachloride Pollution in Groundwater in a Water Source

通过对某水源地地下水的四氯化碳污染调查和日常监测数据分析,研究了该水源地四氯化碳污染晕的形态和变化特征,并选取典型水源井对其四氯化碳动态特征进行了分析。在污染发现初期,污染面积为2.73 km2,最高污染浓度为249.7μg/L,随着后期污染治理工作的开展,污染面积减小到1.24 km2,最高污染浓度下降到3.62μg/L。分析认为,污染晕形态在空间分布上主要受地下水流场的控制,同时受降水量、地下水位标高及开采量等多种因素控制,污染物由北区井群向南区井群扩散。单井四氯化碳含量动态则呈现出南北区的相反特征:在北区,四氯化碳含量随着地下水位的上升而上升,并随地下水流向南扩散;在南区,四氯化碳含量随着地下水位的上升而下降,并随地下水流向地下水漏斗中心汇集。这是由于赋存于SD1井附近包气带中的四氯化碳尚未清除造成的。

Based on the investigation and everyday monitoring data of the carbon tetrachloride （CT） pollution in the groundwater occurring at a water source zone, this paper studies the form of the contaminant plume as well as the changing features, and also it analyzes the dynamic characteristics of the CT in several chosen water source wells. The contaminated area at the initial stage reached 2. 73 km2 , with the max contaminant concentration of 249.7 μg/L. As the pollution control is carried out at the later stage,the contaminated area reduces to 1.24 km^2, with the max contaminant concentration reduces to 3. 62μg/L. The results indicated that the form of contaminant plume was spatially determined by the groundwater flow field as a primary factor, and other factors included precipitation, elevation of groundwater level as well as the yield etc. The contaminant plume extends form the northern wells to the southern ones. In terms of the dynamic content of the CT in a single well, it＇s quite different in the northern and southern areas：for the former, the concentration increases with the rising of the groundwater, and the CT diffusion moves southwards along with the groundwater flow; for the latter, the concentration decreases with the rising of the groundwater, and the groundwater flow carries the CT towards the center of the funnel-shaped zone. The reason for causing such a difference is that the CT formed in the aeration zone near the SD1 well hasn＇t been cleared away.