Effects of Episodic Disturbances on Microbial Degradation of Polycyclic AromaticHydrocarbons (PAHs) in Coastal Sediments

摘要

To examine the effect of disturbance on bacterial PAH transformation insediments, C14 labeled sediment was resuspended into an oxic overlying water column in a flowthrough microcosm system (I-SORES) at resuspension frequencies of 8-12, 4, 1, 0.25 and 0 1/d. Rates of mineralization of C14 naphthalene, phenanthrene and benzo(a)pyrene, modeled as first order processes, were found to increase, along with cumulative mineralization as a function of resuspension frequency. Flux of dissolved compound from the bed was also found to increase with increasing resuspension for all compounds. For the most quiescent treatments (0 and 0.25 1/d ), multi-order kinetics suggested acclimation of bacterial populations. First order rate constants normalized to the fraction of bioavailable solute in pore waters were within an order of magnitude for all three compounds which span three orders of magnitude in hydrophobicity, suggesting that bioavailability is an important control on mineralization. Similarities in the rate and extent of mineralization between naphthalene and phenanthrene was explained by a greater resistance to desorption for naphthalene relative to phenanthrene. Model predictions of phenanthrene mineralization rates, based upon the degree of oxygenation in the different treatments, bracketed measured rates, demonstrating oxygen's control over mineralization.