Evaluation of the role of environmental contamination in the microbial degradation of polyaromatic hyrocarbons

Studies were undertaken to determine the effect of environmental contamination upon the potential for degradation of polyaromatic hydrocarbons (PAH) by the microbial populations in freshwater sediments. Naphthalene (NAP), phenanthrene (PHE), and benzo(a)pyrene (BP) were employed as substrates for PAH biodegradation. Biodegradation was assessed by mineralization of the ¹⁴C-PAH substrates incubated in sediment slurries. Mineralization rate constants and substrate turnover times were calculated for the PAH mineralization studies. Sediment microcosms treated with individual, unlabeled PAH or a synthetic oil (SO) were sampled for the mineralization assay after various periods of acclimation. NAP and PHE treatments enhanced PAH mineralization rates while BP was inhibitory. The SO treatment caused a substantial enhancement of PAH mineralization rates. A PAH-degrading bacterial population added to various sediment systems did not significantly enhance PAH mineralization rates. Studies with natural sediment samples also indicated that previous environmental contamination tends to enhance the potential for PAH biodegradation. Studies indicated PAH mineralization in sediments was related to the length of incubation time, temperature, molecular size of the substrate and prior exposure to PAH or related contaminants.