VOLATILIZATION OF AROMATIC-HYDROCARBONS FROM SOIL .1. FLUXES FROM COAL-TAR CONTAMINATED SURFACE SOILS

The non-steady-state fluxes of aromatic hydrocarbons were measured in the laboratory from the surface of soils contaminated with coal tar Fo ur soil samples from a former gasworks site were used for the experime nts. The fluxes were quantified for 11 selected compounds, 4 mono- and 7 polycyclic aromatic hydrocarbons, for a period of up to 8 or 16 day s. The concentrations of the selected compounds in the soils were betw een 0.2 and 3,100 mu g/g. The study included the experimental determin ation of the distribution coefficient of the aromatic hydrocarbons bet ween the sorbed phase and the water under saturated conditions. The de termined distribution coefficients showed that the aromatic hydrocarbo ns were more strongly sorbed to the total organic carbon including the coal tar pitch - by a factor of 8 to 25 - than expected for natural o rganic matter. The fluxes were also estimated using an analytical solu tion of the Fick's diffusion equation and assuming that the compounds diffused independently of each other and that instant equilibrium exis ted between the air, water and sorbed phases. A relatively good agreem ent was found between the predicted and the measured flux. The predict ed fluxes were between 0.11 and 7.5 time the measured fluxes. The flux es were overestimated for the monocyclic aromatic hydrocarbons and und erestimated for 3-rings-PAHs.