In this study, we present the levels of organochlorine (∑DDT, ∑HCH, ∑chlordane, HCB, and ∑PCBs) and metal (Pb, Hg, and Se) contaminants and their relationship to stable carbon and nitrogen isotope values in the Gulf of the Farallones marine food web. This food web consisted of two species of euphausiids (Euphausia pacifica and Thysanoessa spinifera), two fish species [short-bellied rockfish (Sebastes jordani) and anchovy (Engraulis mordax)], four bird species [common murre (Uria aalge), Brandt's cormorant (Phalacrocorax penicillatus), rhinoceros auklet (Cerorhinca monocerata), and pigeon guillemot (Cepphus columba)], and the northern sea lion (Eumetopias jubatus). We used a novel method of using egg albumen to determine stable isotope values. The values of δ13C ranged from −20.1‰ in the euphausiids to −15.0‰ in the northern sea lion and were consistant with a pelagic/offshore vs benthic/inshore results found in other studies. Values of δ15N in the Gulf of the Farallones food web ranged from 11.2‰ in the euphasiids to 19.8‰ in the northern sea lion and generally demonstrate an equivalence with trophic level. The levels of organochlorine compounds were lowest in the euphausiids [∑DDT 11, and ∑PCB 4.5 μg/kg dry weight geometric mean (GM)] and highest in the northern sea lion blubber (∑DDT 9500 and ∑PCB 3500 μg/kg dry weight GM). The highest levels of organochlorine compounds in the birds were in the common murre (∑DDT 8200 and ∑PCB 5900 μg/kg dry weight GM). Levels of Pb, Hg, and Se ranged from 80 to 1000, from 100 to 19000, and from 1900 to 4100 μg/kg dry weight GM, respectively. All of the organochlorine compounds and Hg were significantly correlated with δ15N values in the food web. Lower values of δ15N in egg albumen than in the muscle tissue from common murres reflect a switch in diet to a lower trophic position during the egg formation period. The high contaminant levels in the murre suggest a mobilization of stored lipids into the eggs.

The presence of PCB contamination in San Francisco Bay has been documented, but the number of sources, their chemical composition, and their geographic/temporal distribution are poorly understood. A self-training pattern recognition technique, polytopic vector analysis is used to determine those parameters from PCBs adsorbed on the particulate fraction of surface waters. Five chemical fingerprints (end-members) were resolved. Four were consistent with published Aroclor patterns. Aroclor 1260 was observed throughout the estuary, in all cruises, with highest proportions observed in Coyote Creek, a tributary of the South Bay. A pattern that matches typical Aroclor 1254 was observed in all cruises but was in generally higher abundance in spring 1995. A second Aroclor 1254 pattern, consistent with an atypical Aroclor 1254 batch described in the literature, was observed in moderate proportions in the three 1996 cruises. Aroclor 1248 was present in significant proportions in only one cruise (cruise 12: July 1996) but was the dominant fingerprint in the Central Bay samples collected at that time. End-member 5 did not match published Aroclor source patterns. Its composition exhibits high proportions of the metabolism-resistant congeners PCB-138 and PCB-153. The source of this pattern is not known, but we hypothesize that it may be due to sewage inputs in the Bay or from atmospheric inputs.

Advances in instrumentation have allowed the measure ment of the isotopic composition of 13C/12C (δ13C) in the effluent of a gas chromatograph for each individual peak; this technique is called compound-specific isotope analysis (CSIA). CSIA has been used in a variety of biogeochemical studies to determine the sources of hydrocarbons. We have utilized the technique of CSIA to examine δ13C of the individual congeners in the polychlorinated biphenyl (PCB) mixtures Aroclor 1242 and 1254; Clophen A30, A50, and T241; Kanechlor 200, 300, 400, 500, and 600; and Phenoclor DP-3, DP-4, DP-5, and DP-6. In addition, the bulk δ13C values (i.e., the entire mixture) were determined for comparison to the CSIA values. Bulk δ13C values ranged from −22.34‰ (Phenoclor DP-3) to −26.95‰ (Clophen A30). The analogues Aroclor 1254, Clophen A50, Kanechlor 500, and Phenoclor DP-5 had different bulk δ13C values. The bulk values fall within the CSIA values and are similar to the average of the δ13C values of the individual congeners. In both the bulk δ13C analysis and the CSIA, the PCBs show increased 13C depletion with increasing chlorine content. Values for congeners within a PCB mixture also showed a wide range of δ13C isotope values; for example, δ13C values in the Kanechlor 600 mixture range from −18.65‰ (PCB 52) to −27.98‰ (PCB 180). Large differences in δ13C values for individual congeners between mixtures were found (e.g., PCB congener 52, Clophen A30−28.35‰ vs Kanechlor 600−18.65‰). The δ13C values for individual congeners in the PCB mixtures showed a similar pattern of 13C depletion with increasing chlorine content, this trend is probably a result of kinetic isotope effects caused by the position of the chlorine atom on the biphenyl molecule. The wide range in δ13C ratios between PCB mixtures and individual congeners may prove to be a powerful tool in the determination of sources of PCBs in the environment, and this technique may have wide applications in environmental chemistry.