Distribution of Parent and Alkylated PAHs in Bivalves Collected from Osaka Bay, Japan

− 11 − ABSTRACT To compare the distributions of polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs (alkPAHs) in sessile marine organisms, bivalves were collected from 20 sites along the coastal areas of Osaka Bay in Japan. Both PAHs and alkPAHs in bivalve tissues were determined by GC/MS. Total PAHs (∑PAHs) were 87.3-361, 212214 and 70.9-351 ng/g dry weight (dw) in blue mussels, green mussels and oysters, respectively. Meanwhile, total alkPAHs (∑alkPAHs) were 466-3293, 950-1788 and 2862787 ng/g dw in blue mussels, green mussels and oysters, respectively. When compared to their reported concentrations in sediments, ∑PAH were much lower while ∑alkPAH were higher in bivalves. Moreover, ∑alkPAHs in bivalves of each samling site were 1.89.8 times higher than ∑PAHs although ∑alkPAHs in sediment of each sampling site were 1.2-4.5 times lower than ∑PAHs. On the other hand, of the PAHs, naphthalene showed the highest concentration in bivalves for most of the sampling sites. Fortunately, benzo(a)pyrene and PAH4 concentrations in bivalves from Osaka Bay were within the EU criteria. For individual alkPAHs in bivalves, the naphthalene, dibenzothiophene, and phenanthrene/anthracene groups were accumulated at relatively high concentrations. These results suggest that the low molecular weight alkPAHs have higher tendency to pollute water columns.