TRANSPORT OF VOLATILE ORGANIC CHEMICALS BENZENE IN THE UNSTATURATED POROUS MEDIA：EXPERIMENTAL STUDIES FOR BENZENE

Based on the State Key Laboratory project“Study on the migration and transformation of the unsaturated zone solute”, conduct isotropic sand and sand with loam interlayer soil column experiments. Benzene as the main line of research, combined laboratory analysis research, research the migration rule of benzene in the unsaturated zone, and provide the basis for the restoration technique. Based on two different cross-sectional configurations soil column, experiment with bromide ions as tracer, and systematic and comprehensive analysis of the benzene migration under constant flow conditions in the unsaturated zone was done. By analyzing the characteristics of water infiltration, matric potential variation with time, migration and distribution of benzene in different soil column, and relations between benzene mobility and bromide ions. There are following conclusions:

1. The benzene adsorption kinetics curve: the characteristic pollutant adsorption equilibrium time of sand was longer than silty loam, about 25h; silty loam adsorption equilibrium time was about 8h and adsorption capacity was more than about 10mg/Kg compared to sand.

2. Benzene adsorption isotherm experiment by using the Henry model: fine sand and silty loam adsorption of benzene gave priority to with linear adsorption, and distribution coefficient Kd_powder> Kd_sand; the adsorption capacity of silty loam is greater than the silt, and the higher clay content, the higher the more easily adsorbed, the higher sand content, the stronger the migration of contaminants.

3. Homogeneous sand soil column wetting front advanced with a certain nonlinear, while, sand loam soil column, when the wetting front in the upper soil wetting front advanced the process was consistent with the former, and then into the layered interface wetting front advancing speed decreased, illustrating that there is a certain infiltration reduction effect of stratification interface.

4. The addition of layered sand loam can significantly change the shape of the curve, and through the initial breakthrough time increased, the slope of the curve becomes smaller; increased clay content result bromine ions and benzene in the soil severely disrupted. The more clay content, the slower speed of the water and solute transport in the soil.