Abstract
Biodegradation rate of polycyclic aromatic hydrocarbons (PAHs) was evaluated using river sediments sampled in Fukuoka Prefecture to assess their fate in the sediment environment. Three sediments (Nos. 1－3) with distinct properties were selected among 18 sediments, and Nos. 1, 2 and 3 were characterized as the samples with PAHs contamination at low, medium and high concentrations, respectively. Fifteen PAHs were spiked to the sediment samples, and they were kept at 20 ℃ in dark during 4 weeks for the biodegradation tests. Significant degradation of naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, and chrysene was observed in No.1 sediment, while Nos. 2 and 3 could degrade only naphthalene, acenaphthene, fluorene, and phenanthrene. The PAHs degradation proceeded most efficiently in No. 1 sediment with the half-lives of the above 9 PAHs of 3－36 days. Although No. 3 sediment was sampled the downstream of the area heavily polluted with PAHs, especially with extremely high level of naphthalene (19,000 μg/g－dry), it was less effective for the PAH degradation than No.1 sediment unexpectedly. The oxidation-reduction potential was measured before and after the degradation tests, and the results showed that No. 1 sediment was kept the most oxidative during the experimental period, suggesting efficient degradation of PAHs in the sediments can occur under oxidative conditions.
