Micellar desorption of polynuclear aromatic hydrocarbons from contaminated soil

Efficacious application of in situ surfactant-aided biodegradation for polynuclear aromatic hydrocarbon (PAH) compounds requires a sound understanding of the behavior of surfactants in these systems. We investigated the desorption of PAH compounds from an aged soil at a former manufactured gas plant site with Alfonic 1412-7, a nonionic alkyl ethoxylate surfactant. When concentrations of Alfonic were lower than twice the critical micelle concentration, PAH desorption was negligible. This was attributed to the sorption of the surfactant to the soil. At higher concentrations, Alfonic significantly enhanced the extent and rate of release of PAH compounds from the soil implying that mechanisms that increased matrix diffusivities in addition to micellar sinks may be operational. Evidence for soil organic matter desorption was also demonstrated.