Uptake and release of polynuclear aromatic hydrocarbons by short-necked clams (Tapes japonica)

We studied the uptake and release of polynuclear aromatic hydrocarbons (PNAHs) by shortnecked clams (Tapes japonica) under the following conditions: exposure to PNAHs dissolved in artificial sea water, in the sediments and in natural sea water. Nine PNAHs, i.e. anthracene, pyrene, benz(a)anthracene, benzo(e)pyrene, benzo(b)flouranthene, benzo(a)pyrene, benzo(g,h,i)perylene, dibenz(a,h)anthracene and 3-methylcholanthrene, were dissolved in artificial sea water at a concentration of 10 ppb each. Index clams were placed in PNAH containing sea water for 7 days and then transferred into the clean artificial sea water for release. Maximal uptake of these substances ranged from 150 to 560 ppb and the release rate (half life) was 4–8 days. While six PNAHs were accumulated by the clams from the sediments during the 7-day exposure, levels of accumulated PNAHs were positively correlated to the PNAH concentrations in the sediments. High accumulation of pyrene, benzo(e)pyrene and benzo(b)fluoranthene were found and their levels in the sediments were correspondingly high. The levels of PNAHs fell to initial levels after the 14-day exposure to the PNAH free sea water. In the PNAH-uptake experiments conducted in the sea, pyrene 14 times the initial amount was accumulated in clams, while the other six compounds were accumulated at 3–8 times. All the PNAH amounts in the clams were determined by HPLC with a fluorescence detector. The results suggest that PNAHs are readily accumulated in clams and these PNAHs in the clams may be a useful biological indicator of PNAH contamination.