Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
As part of the assessment of the potential risk posed by contaminated sediments to the environment and human health, the United States Environmental Protection Agency (USEPA) is developing a set of sediment quality criteria (SQC) that are based on equilibrium partitioning (EqP). While EqP theory has often been used to predict contaminant concentrations within a factor of two for a range of sediment types, substantial deviations from predicted values have also been documented. The objective of this research was to evaluate the influence of PAH source on PAH sediment-pore water partitioning and distribution in sediments. The Elizabeth River is one of three Regions of Concern identified by the USEPA Chesapeake Bay Program. Sediment PAH concentrations, particularly those collected in the vicinity of two former wood-treatment facilities, are elevated in comparison to other regions in the Chesapeake Bay and around the world. Based on an examination of the contaminant levels in the main stem and southern branch of the Elizabeth River using established criteria, the river remains a clear hazard to benthic and pelagic species. A large number of potential sources of PAHs exist in this highly industrialized urban estuary. Employing a combination of principal component analysis (PCA) along with identification of source-specific isomer ratios, contributions from two former wood-treatment facilities were differentiated. Additionally, a significant coal contribution was determined by also incorporating compound-specific carbon isotope ratio analysis (CSIA). Use of CSIA successfully isolated and separated the coal signature from a coal gasification signature, which could not be distinguished using only PCA and isomer ratios. Elizabeth River sediments exhibited a wide range in partitioning patterns indicative of partitioning dominated by different sedimentary fractions including organic carbon, soot carbon, a heterogeneous mixture of sorbents, or dissolved organic carbon. For samples located in the vicinity of former wood-treatment facilities, the presence of non-aqueous phase liquids appeared to strongly influence PAH partitioning despite relatively high levels of soot carbon in the sediments. Outside of localized areas, soot carbon appears to play a dominant role in controlling PAH partitioning, limiting the influence of other factors such as dissolved organic carbon.
© The Author
Walker, Shelby E., "Polycyclic aromatic hydrocarbon sources and distribution in an urban estuary" (2003). Dissertations, Theses, and Masters Projects. Paper 1539616897.