PARENT SESSION
PS8 - Bioaccumulation in Terrestrial Systems
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P107) Bioaccumulation of PCBs in Terrestrial Plants and Invertebrates at Vandenberg AFB, California.
Clark, Donald*,1, Kephart, Bea2, Torres, Kevin1, Shibata, Mark1, Rigby, Mark1, McElligott, Mike2, Waitman, Karen1, 1 Tetra Tech, Inc., Lafayette, CA, USA2 Department of the Air Force, Vandenberg AFB, CA, USA
ABSTRACT- A field validation study in support of ecological risk assessments (ERAs) at Vandenberg Air Force Base (AFB) successfully addressed key uncertainties concerning PCBs. A main objective was to develop regression models to elucidate relationships between PCB concentrations in plant or soil invertebrate tissues and co-located soils. PCB concentrations in tissues and soil were measured across locations comprising both reference and contaminated sites. Exposures of herbivorous and insectivorous wildlife to PCBs were characterized through these regressions. This study improved upon the predictive ERAs by evaluating total PCBs instead of Aroclors, as well as the 14 most toxic individual PCB congeners. PCB concentrations in tissues were lipid normalized to control for variability in the fatty lipids in plants and soil invertebrates. Concentrations of lipid-normalized total PCBs increased in plant tissues (R2 = 0.84) and soil invertebrate tissues (R2 = 0.90) with increasing levels of total PCBs in soil. The individual PCB congeners exhibited similarly strong bioaccumulation relationships. Relative slopes and strengths of the relationships illustrate patterns of PCB accumulation in tissues. The regressions suggest that exposures of insectivorous wildlife to PCBs are higher than those of herbivorous wildlife. Differences between rates of PCB accumulation observed in this study and those predicted using models from the literature are also apparent. We are applying the Vandenberg AFB-specific bioaccumulation regressions to improve the accuracy of exposure estimates for wildlife at other sites with PCB contamination. This study was effective in providing the client and regulators with critical information to reduce uncertainties concerning the risks associated with PCBs.
Key words: pcbs, bioaccumulation, field verification, ecological risk assessment