Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Rebecca M. Dickhut


Sediments and pore waters from two urban estuaries ranging in sediment mixing energy were studied to evaluate the potential release of contaminants from particles during sediment diagenesis. Two sites in Elizabeth River, VA and two tributaries in the Hudson River Watershed were sampled for polycyclic aromatic hydrocarbons (PAHs). Sediment age, total sediment organic carbon (TOC), carbon to nitrogen (C/N) ratios, and particle surface area (SA) were also sampled at these sites. In the Elizabeth River, both sites sampled (Site 1 and Site 2) have been non-depositional for the past 70 y or are comprised of old dredge spoil. PAH K&\sp\prime\sb{lcub}\rm OC{rcub}&s were significantly higher at Site 2 than Site 1 indicating a different type of particle-PAH association at each site independent of the amount of TOC. Decreasing down-core K&\sp\prime\sb{lcub}\rm OC{rcub}&s at Site 1 coincided with down-core change in TOC accessible for PAH binding. at Site 2 in the Elizabeth River, high and uniform K&\sp\prime\sb{lcub}\rm OC{rcub}&s may have resulted from particles with PAHs entrapped by an organic coating. Deposition rates in the East River and Newark Bay were calculated to be &\sim&27 cm/y and &\sim&2 cm/y, respectively. Sediment PAH concentrations were significantly higher in the East River than Newark Bay, coincident with the higher amounts of TOC and SA in East River sediments. Low molecular weight PAHs were not detectable in East River sediments and PAHs were not detectable in East River pore waters. The East River seems to be a site of intense physical mixing where pore water PAHs possibly bound to DOC may be continuously mobilized out of the seabed. In contrast, PAHs in Newark Bay sediments are able to attain equilibrium due to lower intensity of physical mixing. Aspects of sediment geochemistry such as the occlusion of TOC for PAH binding, particle porosity, and amount of pore water DOC may affect PAH distributions in areas where the physical energy of mixing is infrequent or low. PAH distributions in areas that are subject to high energy physical disturbances, may be controlled by the physical energy affecting the system rather than compositional aspects of particulate or pore water dissolved organic matter.



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