Rapidly Desorbing Fractions of PAHs in Contaminated Sediments as a Predictor of the Extent of Bioremediation

Abstract

In the present study, the desorption kinetics of 15 PAHs (two to six rings) from sediments were determined before and after bioremediation in a bioreactor or landfarm. Desorption kinetics were measured with a method in which the water phase was kept PAH-free by Tenax TA beads. For almost all degraded PAHs, rapidly desorbing fractions (desorption rate constants > 0.1 h-1) were much smaller after bioremediation than before treatment whereas the slowly desorbing amounts remained unchanged. Thus, mainly the rapidly desorbing PAHs are degraded during bioremediation. The extent of possible PAH degradation could be roughly predicted from the initial rapidly desorbing fraction. For nondegraded PAHs, the rapidly desorbing fractions were substantial (up to 55%) and remained unchanged by remediation. The magnitude of the rapidly desorbing fractions of the nondegraded PAHs suggests that their persistence is due to microbial factors, not bioavailability.