PW20 New Approaches to Determining Soil and Sediment Exposures
Exhibit Hall
8:00 AM - Wednesday
(PW292) Application of Site-Specific Equilibrium Partitioning Sediment Benchmarks for PAH Mixtures to Manufactured Gas Plants.
Kane Driscoll, S.1, Menzie, C.1, McArdle, M.1, 2, Coleman, A.2, 1 Menzie-Cura & Assoc., Inc., Winchester, MA, USA2 EPRI, Palo Alto, CA, USA
ABSTRACT- This project examines the application of site-specific Equilibrium Partitioning Sediment Benchmarks (ESBs) for assessing the bioavailability and toxicity of polycyclic aromatic hydrocarbons (PAHs) in sediments at former Manufactured Gas Plant (MGP) sites. The major objectives of the study were to: examine whether the ESB approach can be used as a conservative predictor of sediment toxicity at MGP sites and validate the use of the US EPA Bioavailability Procedure, which uses measured concentrations of PAHs in porewater and soot carbon in sediment to develop site-specific ESBs. Samples of sediment were analyzed for total PAHs, total organic carbon, black carbon, sediment toxicity (28-day Hyalella azteca test), and concentrations of PAHs and dissolved organic carbon in porewater. ESB Sum-TUs were calculated based on measured concentrations of PAHs in bulk sediment, measured concentrations of PAHs in porewater, or estimated concentrations in porewater that accounted for binding to black carbon. Results indicate that ESB Sum-TU based on bulk sediment correctly predicted lack of toxicity in sediments with concentrations of total PAHs less than 100 mg/kg, overpredicted toxicity for sediments with concentrations between 200 to 300 mg/kg, and correctly predicted toxicity in sediments with concentrations greater than 300 mg/kg. Sum-TU based on measured porewater concentrations were somewhat variable, overestimating toxicity in fewer samples than estimates based on bulk sediment, but in more samples than estimates that incorporate black carbon. Results indicate that estimates of ESB Sum-TU that incorporate measurements of black carbon are in closest agreement with results of sediment toxicity tests.
Key words: polycyclic aromatic hydrocarbons, Equlibrium Partitioning Sediment Benchmarks, black carbon, porewater