2000 Volume 42 Issue 4 Pages 373-386
Lysimeter experiments were conducted to show relationships between the movement of water and Volatile Organohalogen Compounds (VOC) in an unsaturated zone. TCE and Bromide were used in the experiments to trace respectively the behaviors of VOC and water. Soil properties such as porosity and hydraulic conductivity were measured at eight depths. Soil water potential was measured with tensiometers, while soil water contents were obtained by a neutron soil moisture meter and TDR. Water was sprinkled from the top of the lysimeter in ten experiments. At the beginning of the first experiment, pure TCE and bromide-dated water were put at the surface of the lysimeter. Soil water and soil gas in the unsaturated zone were collected and analyzed during and after rain events. Compared the velocity of infiltrating water with that of TCE, it can be concluded that pure TCE liquid did not always move straight downward, but TCE gas moved more quickly. In addition, there was a tendency to increase TCE gas concentrations with increasing water content. It can be explained either the displacement of high gas concentration downward as a result of percolation of soil water or a desorption of TCE from soil particles.
