SINGLE AND CO-SOLUTE SORPTION OF ORGANIC CONTAMINANTS IN KEROGEN-CONTAINING SEDIMENTS
A difference in PCE sorption magnitude between the upper ~3 m oxidized zone and the deeper reduced matrix of the deposit is attributable to in situ oxidation of the carbonaceous matter. Normalizing the aqueous concentrations by compound solubility for single-solute systems resulted in superposition of the nonlinear isotherms for all of the compounds for a sample from a particular depth. The relationships identified in this work can be used to estimate sorption nonlinearity for specific compounds based on the observed sorption isotherm for a single solute and the fraction organic carbon content of the sediment.
Sorption competition was observed to occur between PCE and t-DCE, and between naphthalene and benzene in samples from ~5 m depth (reduced material). PCE sorption was reduced less in the presence of t-DCE in the oxidized material than in the reduced material. The results of this study demonstrate the importance of considering solute and co-solute concentration effects on contaminant transport retardation. Retardation of a solute can be significantly reduced in the presence of a co-solute, and may be overestimated if the standard empirical method is used.