Aquatic life as biomonitors of dioxin/furan and coplanar polychlorinated biphenyl contamination in the Sacramento-San Joaquin river delta

A pilot study was designed to investigate the extent, magnitude and source of polychlorinated dibenzodioxin and furan (PCDD/F) and coplanar polychlorinated biphenyl (PCB) contamination using aquatic life as biomonitors. The study focused around a bleached pulp and paper mill operating, along with other industrial facilities, near the confluence of the Sacramento and San Joaquin rivers (Delta) in northern California. Four locations were selected for sampling: two upstream from the plant (one on each river), one in the vicinity of the plant and one downstream from the plant. Because of the salinity gradient of the riverine system, no single fish or bivalve species could be collected, but multiple comparisons were made instead. The target species were selected on the basis of their abundance and localized feeding range. Clams were transplanted in the three freshwater locations and retrieved two months later, while resident mussels were collected from the estuarine location. Surface sediment samples were collected from each location. Whole body fish samples were composited or analysed individually based on size. The samples were freezedried, cleaned by a modified Smith-Stalling procedure, and the coplanar PCBs and PCDD/Fs were isolated and analysed by HRGC/HRMS. Low levels of PCDD/Fs were found in all samples: 1–3 pg/g TEQ (wet wt) in fish; 1–5 pg/g I-TEQ (dry wt) in bivalves; and from 3–51 pg/g I-TEQ (dry wt) in sediments with variable PCB levels. With few exceptions, only 2,3,7,8-substituted PCDD/Fs were found in fish, whereas bivalves had both 2,3,7,8-substituted and non-2,3,7,8-substituted PCDD/Fs with relatively high levels of total TCDDs compared to total PeCDD or HxCDD. Sediments had a PCDD/F pattern consistent with pentachlorophenol contamination. Comparison of sediments and collocated bivalves did not indicate bioconcentration in PCDD/Fs, but it did reveal a tenfold increase in PCB #77 and #126. Within each sample type, the PCDD/F and PCB congener profiles were consistent across species and locations. Shifts in congener profiles from sediments to bivalves to fish were consistent across locations. From the available data, the influence of the pulp mill, if any, could not be distinguished from the other sources in the region.