Sorption of Naphthalene onto Natural and Surfactant-Amended Soils

Surfactant amendment has been proposed as a means to stabilize or mobilize groundwater contamination by modifying the soil's natural sorption characteristics in situ. The importance of the native soil's characteristics with regard to contaminant sorption and the effect of surfactant amendment were evaluated using three varied soil samples and naphthalene as a model contaminant. As expected, soils with high cationic exchange capacity and organic matter content tend to have the greatest ability to sorb naphthalene and the surfactant cetylpyridinium chloride. Micelle formation was noted in the presence of weakly sorbing natural soil, though not in the more reactive soil samples. Surfactant amendment significantly increased naphthalene sorption capacity for sterilized, nonreactive sand, increasing the partitioning coefficient, Kd, by 50%, and decreasing sorption among soils with high natural sorption capacity, partitioning naphthalene back into the aqueous phase.