Effects of soil environment changes on the behavior of VOC's in unsaturated zone

摘要

Behavior of Volatile Organic Compounds (VOC's) in an unsaturated-saturated capillary zone plays an important role in the understanding of pollutant mechanisms. Most of the previous experimental studies had problems of scale, temperature and size of porous media. Lysimeter experiments were than conducted to study the behavior of VOC's in unsaturated zone by simulated rain. TCE and Bromide were used in the experiments to trace respectively the behavior of VOC's and water. By comparing the vertical profile of bromide and the one of TCE, it was found that liquid's TCE does not always move straight downward to the water table. It rather remains at the top layer, while TCE gas moves faster than water. This is considered to be the result of downward pushing of water with dissolved TCE and TCE gas by percolating water. Furthermore, heterogeneous soil property, one of the factors causing the distribution of VOC's is also discussed.