UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

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 given thesis/dissertation in DRUM.

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

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    Contaminants in the atmosphere of the Delmarva Peninsula: impact of local activities and atmospheric transport
    (2007-04-10) Goel, Anubha; Torrents, Alba; McConnell, Laura L; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Anubha Goel, Doctor of Philosophy, 2007 Upper Delmarva Peninsula (within the Chesapeake Bay watershed), where the land use is predominantly agricultural, may be a significant source of pesticides (contributors in the declining water quality and bio-diversity of associated wetlands of the Chesapeake Bay) to the region. Although the Peninsula is predicted to be receiving significant inputs of herbicides through atmospheric deposition, the extent of local or regional atmospheric transport and deposition of pesticides to this area is poorly understood. The goal of this research was to determine the atmospheric levels and estimate deposition flux of pesticides in the Upper Delmarva Peninsula. This was accomplished by collecting weekly air samples (n=271) and event based rain samples (n=489) from three locations in the region (Dover and Lewes, DE; Cambridge, MD) for the period 2000-2003. The samples were analyzed for the presence of 34 pesticides (19 current use (CUPs), 15 historical (HUPs)) and 4 congeners of penta-BDE (PBDEs) using gas chromatograph-mass spectrometry (GC-MS). Statistically analyzed data was used to evaluate factors impacting phase distribution and the contribution of wet deposition to the levels in Chesapeake Bay. The more persistent insecticides and fungicides occur ubiquitously while application on corn influences herbicide occurrence and levels. Atmospheric CUP levels are driven by regional agricultural activity. CUPs do not exist in equilibrium and local meteorological conditions (like high relative humidity) influence phase distribution. The wet deposition flux of insecticide and fungicide is dependent on the total rainfall amount during the sampling period while timing and frequency relative to application on corn impacts herbicide flux. Levels in rainwater of some pesticides (endosulfans, chlorothalonil, diazinon etc.) were high enough to be of concern for the biota associated with the region's water bodies and associated wetlands and reveals that atmospheric deposition arising out of short range atmospheric transport can result in significant pesticide input to non-target areas. HUP atmospheric levels are lower than in the Great Lakes and are decreasing at a faster rate. This study reveals that spray irrigation of treated wastewater is an unknown source of toxic PBDEs to the atmosphere and can result in elevated levels at locations downwind of the irrigation field
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    Investigating Uncertainties in Trace Gas Emissions from Boreal Forest Fires Using MOPITT Measurements of Carbon Monoxide and a Global Chemical Transport Model
    (2005-08-02) Hyer, Edward Joseph; Kasischke, Eric S; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Boreal forest fires are a significant contributor to atmospheric composition in the high northern hemisphere, and are highly variable both spatially and temporally. This study uses a new emissions model [Kasischke et al., 2005] to generate input to the University of Maryland Chemical Transport Model [Allen et al., 1996], with the goal of examining and constraining the key uncertainties in current understanding of boreal forest fire behavior. Model outputs are compared with data from the MOPITT instrument as well as in situ measurements of CO. A case study of CO transport during the summer of 2000 is used to examine several key uncertainties in the emissions estimates, describing how current levels of uncertainty affect atmospheric composition and applying atmospheric measurements can be applied to constrain uncertainty. Source magnitudes determined by inverse methods were shown to be highly sensitive to the assumed injection properties. For the boreal forest in 2000, the best agreement with observations was obtained with a pressure-weighted profile of injection throughout the tropospheric column, but detailed examination of the results makes clear that any uniform parameterization of injection will be a significant source of error when applied globally. Comparison of simulated CO distributions from daily, weekly, and monthly aggregate emissions sources demonstrated that while model data sources produced a valid representation of emissions at weekly resolution, the atmospheric distribution outside the source region has very little sensitivity to temporal variability at scales finer than 30 days. Different estimates of burned area produced large differences in simulated patterns of atmospheric CO. The GBA-2000 global product and the data sources used by Kasischke et al. [2005] gave better agreement with atmospheric observations compared to the GLOBSCAR product. Comparison of different estimates of fuel consumption indicated that atmospheric measurements of CO have limited sensitivity to spatial variability in fuels, but that current fuels maps can improve agreement with atmospheric measurements. These results provide a clear indication of how atmospheric measurements can be used to test hypotheses generated by emissions models.