Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Characterization of PAH Composition Patterns in Diesel Emission
    (2007-01-22) Minegishi, Taeko; Baker, Joel E.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Particles and gases emitted by diesel vehicles can be toxic to human health. Polycyclic aromatic hydrocarbons (PAHs) and nitrated-PAHs (NPAHs) can be used as tracers to identify the contribution of diesel exhaust to the atmosphere. Air samples were collected near the Peace Bridge in Buffalo, NY, where studies have shown an association between asthma patients and traffic on the Peace Bridge. Positive Matrix Factorization (PMF) was used to estimate the source profile and the relative contribution of unknown emission sources. Four PAH sources identified were regional-scale volatilization, vehicle particulate matter, tar/asphalt volatilization, and diesel exhaust. Three NPAH sources identified were NO3 radical reaction, diesel exhaust and mixed sources. Volatilization was the major source of PAHs and NO3 radical reactions were the largest source of NPAHs in Buffalo, NY. Diesel exhaust accounted for approximately 30% of PAH and 18% of NPAH at the sampling site closest to the Peace Bridge.
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    SUBLETHAL NARCOTIC IMPACTS OF DIETARY POLYCYCLIC AROMATIC HYDROCARBONS ON THE BIOENERGETICS OF AND POLYCHLORINATED BIPHENYL (PCB) BIOACCUMULATION IN FUNDULUS HETEROCLITUS
    (2005-09-27) Merten, Amy; Mason, Robert P; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Accumulation of non-polar narcotic chemicals in organisms alters their metabolic rates and therefore, their energetic demands. It is hypothesized that decreases in standard metabolic rate from accumulation of narcotics reduces feeding. Thus, exposure to and accumulation of narcotics may cause a negative feedback, reducing net bioaccumulation. Three experiments were conducted to examine the consequences of narcotic exposure on the bioenergetics and bioaccumulation rates of Fundulus heteroclitus continuously challenged with sublethal levels of hydrophobic organic chemicals (HOCs). In the final experiment (120 days), fish were exposed to two concentrations of a model narcotic, 3-aminobenzoic acid ester methanesulfonate (MS-222) (0 and 50 mg/L), and four concentrations of PAH-contaminated food treatments sampled over five time points. All food treatments contained background concentrations of polychlorinated biphenyl (PCB) congeners (40 ng/g -PCBs w/w) and were used as a tracer of bioaccumulation. No statistically significant differences in weight, length, or condition factors among treatments, except on day 120 where MS-222 exposed fish were longer than non-MS-222 exposed fish (p = 0.015). Standard metabolic rate responded in a non-linear manner. At low PAH doses (835 ng/g -PAH), SMR decreased significantly (p = 0.093,  = 0.10). Fish fed 100% PAH-contaminated food (regardless of MS-222), had significantly elevated SMRs (p = 0.02). MS-222 did not affect PCB accumulation. PAH-contaminated food enhanced PCB accumulation measured in fish. There was an overall interaction between the food treatment and aqueous MS-222 exposures (p = 0.004). The results indicate that total chemical burden from the MS-222 plus PAH-contaminated food exposures masked the sublethal narcotic effect of MS-222, and produced a net increase in the standard metabolic rates of Fundulus heteroclitus, perhaps because of increased energetic costs associated with detoxification and bioactiviation processes. The results of the experiments were subtle and non-linear with respect to dose of PAH-contaminated food. To explore whether small changes in SMR (± 5 - 10 %) may be important costs, a bioenergetics model was developed. The model tracks biomass (daily age classes) based on a balance of weight-specific consumption and bioenergetic costs (respiration, growth, and mortality). The model projects population biomass as the main output for comparing different "impacts."