Analysis of Diffusion and Sorption of Chlorinated Hydrocarbons in Soil by Single-Pellet Moment Technique

The single-pellet moment technique was shown to be a powerful method for investigating the diffusion and adsorption of volatile hydrocarbons in the soil. The technique was used to evaluate effective diffusivities, adsorption equilibrium, and rate constants of chlorinated hydrocarbons (monochloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane). Results obtained in a dry system showed that adsorption rate constants of all these hydrocarbons on the soil pellet used are of the same order of magnitude (4.4-8.0 cm3 g-1 s-1). On the other hand, molecules having chlorine atoms bonded to the same carbon atom (monochloroethane, 1,1,1-trichloroethane) have adsorption equilibrium constants about 1 order of magnitude smaller than these for molecules containing chlorine atoms bonded to different carbon atoms (1,1,2-trichloroethane, 1,2-dichloroethane).