Biodegradation of sorbed fluorene in sediment slurries

The bioavailability of sorbed organic chemicals is a deciding factor in the applicability of bioremediation processes to contaminated sediments and soils. Sorption of pollutants may prevent contact between the microbes and the contaminant, or it may simply maintain the aqueous phase contaminant concentrations at levels too low to support growth. Studies presented herein investigate the biodegradation and desorption of fluorene, a 3-ringed polynuclear aromatic hydrocarbon (PAH), in estuarine sediment-water slurries. Adsorption of fluorene to sediments with 1.4% organic carbon was characterized with a linear isotherm. Desorption was characterized through step-desorption and temporal-desorption tests, which showed that desorption was both completely reversible and rapid. Further studies evaluated the rate and extent of fluorene removal in systems containing a fluorene-degrading culture. Fluorene biodegradation was confirmed with C-14 mass balance experiments, and fluorene disappearance was monitored in both the sediment and aqueous phase. In biologically active systems fluorene was rapidly degraded, after a lag period, to levels below detection limits. The rate of fluorene disappearance in biologically active systems was controlled by microbial degradation rates and was not Limited by desorption.