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Abstract: Bivalve tissue samples were examined over a range of spatial and temporal scales (1993–2001) to determine PAH distributions, trends, and possible sources. Mussels (Mytilus californianus), oysters (Crassostrea gigas), and clams (Corbicula fluminea) were deployed for three months in the estuary at stations remote from known point source discharges. The range of ∑PAH detected in bivalves was oysters 184–6899μg/kg dry wt (mean 678μg/kg dry wt), mussels 21–1093μg/kg dry wt (mean 175μg/kg dry wt), and clams 78–720μg/kg dry wt (mean 323μg/kg dry wt). Linear regression analysis showed no statistically significant (p >0.05) temporal trends in clam and mussel ∑PAH at any of the deployment stations or estuary segments. On the other hand, a statistically significant (p <0.05) decreasing trend was found in ∑PAH in oysters at the Petaluma River station, and in the North Estuary segment. PAH isomer pair ratios applied as diagnostic indicators suggested that the bioaccumulated PAH were derived primarily from petroleum combustion, with lesser amounts derived from biomass and coal combustion, and unburned petroleum. [Copyright &y& Elsevier]

The composition of PAH in surface waters was examined over a range of spatial and temporal scales to determine distributions, trends, and possible sources. Water samples were collected from 1993 to 2001. PAH in organic extracts were analyzed by gas chromatography–mass spectrometry (GC–MS) and 25 individual target PAH summed to get the total PAH concentration in each water sample. The distribution of median total PAH concentration by estuary segments was Extreme South Bay (120ngl−1)>South Bay (49ngl−1)>North Estuary (29ngl−1)>Central Bay (12ngl−1)>Delta (7ngl−1). Overall, total PAH concentrations were significantly higher in the Extreme South Bay compared to all other segments, and the Central Bay and Delta were significantly lower than all other segments (Kruskal–Wallis, H=157.27, df=4, p<0.0005). This distribution reflects the large urbanized and industrialized areas that border the southern portions of the estuary and the less populated and rural areas that surround the Delta. Temporal trend analysis showed a statistically significant temporal trend in total PAH concentration at only one of the 18 sampling stations situated throughout the estuary (San Jose, significant decrease, p=0.031, r2=0.386, n=12). PAH isomer pair ratio analysis showed that PAH in estuary waters were derived primarily from combustion of fossil fuels/petroleum (possible PAH source contributors include coal, gasoline, kerosene, diesel, No. 2 fuel oil, and crude oil) and biomass (possible contributors include wood and grasses), with lesser amounts of PAH contributed from direct petroleum input. [Copyright &y& Elsevier]