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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]

Urban watersheds are significantly anthropogenically-altered landscapes. Most previous studies cover relatively short periods, without addressing concentrations, loads, and yields in relation to annual climate fluctuations, and datasets on Ag, Se, PBDEs, and PCDD/Fs are rare. Intensive storm-focused sampling and continuous turbidity monitoring were employed to quantify pollution at two locations in the Guadalupe River (California, USA). At a downstream location, we determined loads of suspended sediment (SS) for 14 yrs., mercury (HgT), PCBs, and total organic carbon (TOC) (8 yrs), total methylmercury (MeHgT) (6 yrs), nutrients, and trace elements including Ag and Se (3 yrs), DDTs, chlordanes, dieldrin, and PBDEs (2 yrs), and PCDD/Fs (1 yr). At an upstream location, we determined loads of SS for 4 yrs. and HgT, MeHgT, PCBs and PCDD/Fs for 1 yr. These data were compared to previous studies, climatically adjusted, and used to critically assess the use of small datasets for estimating annual average conditions. Concentrations and yields in the Guadalupe River appear to be atypical for total phosphorus, DDTs, dieldrin, HgT, MeHgT, Cr, Ni, and possibly Se due to local conditions. Other pollutants appear to be similar to other urban systems. On average, wet season flow varied by 6.5-fold and flow-weighted mean (FWM) concentrations varied 4.4-fold, with an average 7.1-fold difference between minimum and maximum annual loads. Loads for an average runoff year for each pollutant were usually less than the best estimate of long-term average. The arithmetic average of multiple years of load data or a FWM concentration combined with mean annual flow was also usually below the best estimate of long-term average load. Mean annual loads using sampled years were also less than the best estimate of long-term average by a mean of 2.2-fold. Climatic adjustment techniques are needed for computing estimates of long-term average annual loads. [ABSTRACT FROM AUTHOR]