Biodegradation of polycyclic aromatic hydrocarbons in sediments from the Daliao River watershed, China

The Daliao River, as an important water system in Northeast China, was reported to be heavily polluted by polycyclic aromatic hydrocarbons (PAHs). Aerobic biodegradations of four selected PAHs (naphthalene, phenanthrene, fluorene and anthracene) alone or in their mixture in river sediments from the Daliao River water systems were studied in microcosm systems. Effects of additional carbon source, inorganic nitrogen and phosphorus, temperature variation on PAHs degradation were also investigated. Results showed that the degradation of phenanthrene in water alone system was faster than that in water-sediment combined system. Degradation of phenanthrene in sediment was enhanced by adding yeast extract and ammonium, but retarded by adding sodium acetate and not significantly influenced by adding phosphate. Although PAHs could also be biodegraded in sediment under low temperature (5 degrees C), much lower degradation rate was observed. Sediments from the three main streams of the Daliao River water system (the Hun River, the Taizi River and the Daliao River) demonstrated different degradation capacities and patterns to four PAHs. Average removal rates (15 or 19 d) of naphthalene, phenanthrene, fluorene and anthracene by sediment were in the range of 0.062-0.087, 0.005-0.066, 0.008-0.016 and 0-0.059 mg/(L x d), respectively. As a result, naphthalene was most easily degraded compound, anthracene was the hardest one. In multiple PAHs systems, the interactions between PAHs influenced each PAH biodegradation.