| Research Abstract |
We investigated the fluctuation of mutagenicity and polyaromatic hydrocarbons (PAHs) in the sewage water obtained from several treatment steps at one of the Tokyo Metropolitan combined sewer plants. The sample waters (10L each) were collected at four different points
1) incoming raw water
2) aerating tank
3) just before chlorine treatment plant
4) outgoing water
Each sample water was fractionated into a fiItrate and a residue. The filtrate was concentrated 500 times and treated with dichloromethane (DCM) 3 times to extract active compounds. The residue was treated with methanol and then with DCM to extract high and low polar compounds, respectively. Sampling was conducted under continuous fine weather and heavy rains. Direct extraction of the active compounds was also carried out using a Blue Rayon (BR),which has a high absorbing capacity to PAHs,and compared its recovery ratio to our extraction method.
Mutagenicity was determined by Forward mutation assay using Salmonella typhimurium TA 677
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and the highest activity was detected in the aerating tank and incoming waters (7.719 and 2.139 x 10^<-6>/ml/plate, respectively) without the presence of S9. The remaining two samples were pseudo-positive and thought to be not seriously harmful to fisheries environment at the present.Under the presence of S9,no mutagenicity was detected from any sample including BR extract.
Acenaphthylene, pyrene, and benzo(a) anthracene were the major PAHs distributed over 0.2ng/L in all samples regardless of the weather condition. In the case of BR extraction, only 1 to 11% of the total PAHs was recovered compared to the sample prepared by our extraction method.
From these results, mutagenicity and the concentration of PAHs released from the combined sewer plant looked not serious at the time, but long term exposure of marine organism to genotoxicity must be unfavorable from the view point of food chain. BR method for extracting the mutagenic compounds might sometime overlook considerable part of the genotoxic activity. Less
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