STUDY ON THE MECHANISMS OF POLLUTANTS ON SOIL AND GROUNDWATER

点击翻译按钮获取中文摘要

20 years has passed since the first case of groundwater pollution caused by VOCs. By now, there were many methods and technologies developed for soil and groundwater pollution investigation as well as remediations. As well known, movements of VOCs in soil and goundwater are mostly controlled by hydrogeological conditions. In this research, we investigated mechanisms of VOCs migrations in soil and groundwater in three scales: indoor experiment, lysimeter experiment and in site experiment.1 Results of indoor experimentsThe underground distributions of NAPLs are effected by the water table changes due to pumping, air sparging, infiltration etc. around the pollution sources. It is clear that variations of water table can make TCE and benzene movable by changing balances among water, air and them. During the water table moves up, TCE body keeps still and benzene body tends to move together and may be intercepted by water and trapped in saturated zone. Both of trapped TCE and benzene in saturated zone may change its shape, and never move up in spite of variations of the water table. Therefore, DNAPLs are trapped by water more easily than LNAPLs. On the other hand, during the water table moves down, TCE body changes its shape from flat to long bar and increase its entry pressure, but benzene only spreads laterally to expand its distribution area.2.Results of lysimeter experimentsGenerally, infiltrating water can push both TCE-dissolved-water and TCE gas downward during rain events. It means that TCE can move with infiltraing water by dissolution and TEC gas can move down through the soil due to sealing porous pores and compressing gases in the unsaturated zone during the events.3.Results of in site experimentsVOCs can change the hydraulic conductivities of soil. As a results, distributions of both water and VOCs became very complicated, which must effect on the remediation efficiency.