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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]

The objectives of this study were to examine surface sediments in the San Francisco Estuary for PAH composition over a range of spatial and temporal scales to determine distributions, trends, and possible sources. Surface sediments (top 5 cm) were collected at 26 sites from 1993 to 2001. The mean total PAH (∑PAH) concentration in sediments was spatially distributed as Central Bay (230 mg/kg TOC), South Bay (217 mg/kg TOC), North Estuary (96 mg/kg TOC), Extreme South Bay (87 mg/kg TOC), and Delta (31 mg/kg TOC). Overall, the mean ∑PAH concentrations were significantly higher in the Central Bay and South Bay segments compared to the North Estuary, Extreme South Bay and Delta segments, and the Delta was significantly lower than all other segments (Kruskal–Wallis, H=156.94, df=4, p=0.000). In addition, no significant difference in ∑PAH concentration was found between the Central Bay and South Bay. This distribution reflects the large amount of urbanized and industrialized areas that surround the Central Bay and South Bay compared to the less urbanized and rural areas surrounding the Delta. Temporal trend analysis showed a statistically significant temporal trend in ∑PAH concentration at only 1 of the 26 sampling sites located throughout the estuary (San Pablo Bay, significant decrease, p=0.024, r2=0.314, n=16), which suggests that ∑PAH concentrations in the estuary generally remained constant from 1993 to 2001. Source analysis using PAH isomer pair ratios as indicators showed that PAH are derived primarily from combustion of fossil fuels/petroleum (gasoline, crude oil, and coal) and biomass (wood and grasses), with minor amounts of PAH derived from direct petroleum input. [Copyright &y& Elsevier]