Objective

Sediment beds at many Department of Defense (DoD) sites are contaminated with hydrophobic organic compounds (HOC). These HOCs are persistent and tend to bioaccumulate. In order to improve the fundamental understanding of chemical sorption to real world sediments, the role of black carbons (BC) (e.g., soots, chars, coal dust) in these deposits needs to be elucidated. Such BC sorption greatly reduces the bioavailability of a wide range of organic contaminants. This improved understanding will have several important impacts, including improved understanding and modeling of bioavailability when site managers are using sediment concentration data, enhanced means to use and interpret passive samplers when assessing wide arrays of target compounds using only a few performance reference compounds, insights to kinetic limitations associated with phenomena like contaminant desorption from resuspended sediments, an ability to pre-judge the sorption of a far more diverse array of organic contaminants, and more accurate expectations for risk reduction associated with remedial efforts since BC sorption exhibits nonlinear behavior.

The overarching objective of this project is to improve the fundamental understanding of organic chemical sorption to BCs in sediments while providing a practical means for evaluating this interaction quantitatively. This can be done by elucidating the polyparameter linear free energy relationship (ppLFER) parameters needed to evaluate HOC partitioning between aqueous solution and the water-wet surfaces of BCs, i.e., the compounds' K_BC and Freundlich n values, for any compound of interest.