MIGRATION OF CHLORINATED-HYDROCARBON SOLVENTS THROUGH COVENTRY SANDSTONE ROCK COLUMNS

The migration in the Coventry sandstone aquifer system of aqueous solu tions of various chlorinated hydrocarbon solvents (CHSs) (1,1,1-trichl oroethane (TCA), trichloroethylene (TCE) and tetrachloroethylene (TeCE )) was studied by means of percolation experiments with undisturbed ro ck cores. The retardation factor (Rf) was very low (always less than 2 for TCA, less than 3 for TCE and less than 5 for TeCE). The Rf varied slightly according to the nature of the solid sample but could not be related to the solid organic carbon content. The solvent adsorption w as always almost completely reversible and little affected by the perc olation flow rate (0.08-0.56 m day-1). The CHS breakthrough curves wer e typical of non-equilibrium processes (caused by sorption by the soli ds and possibly by diffusion between mobile and immobile water). The R f values obtained experimentally were much lower than those calculated from batch adsorption studies, showing that percolation experiments a re necessary to evaluate the filtering properties of consolidated rock s. These results indicate that in the Coventry sandstone aquifer (rela tively high vertical and, especially, lateral hydraulic conductivities ), two-carbon CHS aqueous solutes should migrate readily with water wi th very little retardation.