水環境の改善と修復 多摩川河口域低泥表層における石油化学物質の微生物による分解浄化

Abstract

The objective of this study is to determine aerobic and anaerobic biodegradation rates of hexadecane (HEX), phenanthrene (PHE), and anthracene (ANT) using estuarine sediments of Tama River in Tokyo and to estimate degradation potentials of these petroleum hydrocarbons in estuarine sediment of Tama River. Known amounts of these petroleum hydrocarbons were added to sediment slurry prepared by mixing estuarine sediment with bottom water in Tama River (sediment : water=1 : 1 v/v). Sediment slurry was incubated by reciprocal shaking in aerobic and anaerobic condition at 20°C. After sediment slurry was sampled periodically and extracted with ethyl acetate, these petroleum hydrocarbons in sediment were determined by gas chromatography with FID. In aerobic incubation series, the cells number of total heterotrophic bacteria and HEX-, PHE-, or ANT-utilizing bacteria in sediment slurry was determined. Aerobic biodegradation rates of HEX, PHE, and ANT in sediment slurry ranged from 40 μg·g-1 dry sediment·day-1 to 70μg·g-1 dry sediment·day-1. Anaerobic biodegradation rates of HEX were 5-8 μg·g-1 dry sediment·day-1. But, biodegradation of PHE and ANT was not observed during the two-month incubation period. Aerobic degradation of HEX was not affected by existence of PHE or ANT. The mumber of HEX-, PHE- or ANT-utilizing bacteria was 5-10 percentage of total heterotrophic bacteria in estuarine sediment. Biodegradation potentials of petroleum hydrocarbons in estuarine sediment of Tama River calculated from biomass of the utilizing bacteria in estuarine sediment and biodegradation rate per cell of utilizing bacteria in the period of constant biodegradation being observed were 1.0-3.5μg·g-1 dry sediment·dry-1 of HEX and 1.2×10-2-4.2×10-2μg·g-1 day sediment·day-1 of PHE or ANT.