Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Rebecca M. Dickhut
The relationship between wetland polycyclic aromatic hydrocarbon (PAH) concentrations and adjacent land use was assessed using surface sediments, sediment cores and global information systems (GIS) in the Elizabeth River, Virginia, an urbanized subestuary of the Chesapeake Bay. Wetlands adjacent to parking lots and petroleum industrial sites exhibited the highest PAH concentrations of all land uses in surfaces sediment and historically. Automobile and coal are the dominant sources of PAHs in wetland sediments historically as determined by relative concentration, fingerprinting and source specific compounds. An analysis of variance (ANOVA) test used to compare sixteen surface sediment sites based on land use revealed significant differences in wetland surface sediment PAH concentration. Multi-family and single-family residential, rural, undeveloped, commercial, petroleum industrial and non-petroleum industrial most accurately identified distinct land use categories in the watershed. Source assessments revealed little variability between sites, which is indicative of one atmospheric source of PAHs to wetland surface sediments. Concentration magnitude and source similarities implicate percent impervious surface and proximity to sources as having a major influences on PAH input to wetlands. GIS and surfaces sediment PAH concentrations were used to assess wetland area, adjacent land use in addition to PAH storage, distribution and input at the micro (site) and macro (watershed) scales. Despite urban wetlands having the largest concentration of PAHs a disproportionately low number of associated wetlands resulted in lower PAH storage at the macro scale. Residential, urban and rural wetlands contained the largest amounts of PAHs respectively. Wetland migration and erosion make wetlands dynamic sinks that constantly release and accumulate contaminants as they migrate shoreward to keep pace with sea level rise. In the urban Elizabeth River over 75% of wetlands are not able to migrate as a result of upland development. A conceptual model depicting wetland migration with developed and undeveloped uplands, and variable PAH source in sediments indicate wetlands can act as sources or sinks of slowly degrading contaminants. PAH flux measurement determined from wetland surface sediment concentrations and accretion rates showed PAH flux to all wetlands were exponentially higher than atmospheric deposition.
© The Author
Kimbrough, Kimani L., "Effects of urbanization and land use on PAH accumulation in wetland sediments" (2002). Dissertations, Theses, and Masters Projects. Paper 1539616718.