Light microscopy and petrography images of the four most abundant and relevant particle types present in Manufactured Gas Plant site sediments.

The Determination of Sediment Polycyclic Aromatic Hydrocarbon (PAH) Bioavailability using Supercritical Fluid Extraction (SFE) and Ultra-Trace Porewater (UTP) analysis.

D. Nakles, A. Hawkins, S. Hawthorne, T. S. Bridges, U. Ghosh.
Duration: 2008-2010
Funding agency: Environmental Security Technology Certification Program (DoD)

Summary. Studies of the bioavailability and toxicity of PAHs in sediments have shown that the use of total PAH concentrations to predict aqueous concentrations in porewater often overestimates the risk to aquatic organisms. The observed lack of toxicity at high sediment PAH concentrations has been attributed to the fact that these compounds are much more strongly bound to sediment organic carbon than is assumed by the standard equilibrium partitioning model. Mild supercritical fluid extraction (SFE) using carbon dioxide has been shown to be a good estimator of PAH bioavailability to benthic macro invertebrates in freshwater sediments, and ultra-trace porewater (UTP) analysis using solid phase microextraction (SPME) has been used to accurately measure the dissolved concentration of PAHs in sediment porewater. Both of these methods have been demonstrated to successfully predict the toxicity of freshwater sediments with much greater accuracy than is achieved by the use of generic sediment screening guidelines based on total PAH concentrations.

The proposed demonstration/validation project is designed to build upon the data developed to date demonstrating how site-specific estimates of PAH bioavailability in freshwater sediments can be used to predict toxicity to benthic freshwater species. The goal of the proposed project is to extend the application of SFE and UTP estimates of PAH bioavailability to marine/estuarine sediments and species. Specifically, the project objectives are to 1) use SFE and UTP analyses to predict the bioavailability of PAHs in marine/estuarine sediments collected from two Navy facilities, 2) show the relationship between predictions of PAH bioavailability and the actual measured toxicity to a marine/estuarine macro invertebrate species and 3) demonstrate the application and develop technical guidance on the use of SFE and UTP as site-specific measurements of PAH bioavailability for assessing risk.