In the present study it was demonstrated that organic additives eluted from plastic resins could be utilized as substrates by sulfate-reducing bacteria. Two laboratory-scale experiments, a microcosm experiment and a leaching experiment, were conducted using polyvinyl chloride (PVC) as a model plastic resin. In the former experiment, the conversion of sulfate to sulfide was evident in microcosms that received plasticized PVC as the sole carbon source, but not in those that received PVC homopolymer. Additionally, dissolved organic carbon accumulated only in microcosms that received plasticized PVC, indicating that the dissolved organic carbon originated from additives. In the leaching experiment, phenol and bisphenol A were found in the leached solutions. These results suggest that the disposal of waste plastics in inert waste landfills may result in the production of H(2)S.

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.