Vertical transport of chlorinated hydrocarbons in unsaturated zone including effect of rainfall

Abstract

Chlorinated hydrocarbons (CHCs) are highly volatile and little soluble in water, and can exist in unsaturated zone as vaporized, dissolved and undiluted non-aqueous phases. Therefore, it is of great importance to understand transport mechanism of CHCs with gas advection and diffusion in unsaturated zone, and then numerical analysis for vertical transport of CHCs in unsaturated zoneincluding effect of rainfall was conducted. Vertical one-dimensional fluid flow equations and mass transport equations for water and gas phases, and two layer model for mass transfer between the phases were employed in the model presented. The results showed that, though gas phase transport is usually dominant during dry period in unsaturated zone, transport in water phase overcomes that in gas phase during rainwater percolating period.