RAPIDLY DESORBING FRACTIONS OF PAHS IN CONTAMINATED SEDIMENTS AS A PREDICTOR OF THE EXTENT OF BIOREMEDIATION

In the present study, the desorption kinetics of 15 PAHs (two to six r ings) from sediments were determined before and after bioremediation i n a bioreactor or landfarm. Desorption kinetics were measured with a m ethod in which the water phase was kept PAH-free by Tenax TA beads. Fo r almost all degraded PAHs, rapidly desorbing fractions (desorption ra te constants > 0.1 h(-1)) were much smaller after bioremediation than before treatment whereas the slowly desorbing amounts remained unchang ed. Thus, mainly the rapidly desorbing PAHs are degraded during biorem ediation. The extent of possible PAH degradation could be roughly pred icted from the initial rapidly desorbing fraction. For nondegraded PAH s, the rapidly desorbing fractions were substantial (up to 55%) and re mained unchanged by remediation. The magnitude of the rapidly desorbin g fractions of the nondegraded PAHs suggests that their persistence is due to microbial factors, not bioavailability.