Civil & Environmental Engineering

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    MODELING OF MINERAL TRAPPING FOR CO2 SEQUESTRATION
    (2011) Alizadeh Nomeli, Mohammad; Riaz, Amir; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In order to prevent CO2 concentrations in the atmosphere from rising to unacceptable levels, carbon dioxide is sequestered beneath the ground surface. CO2 can be trapped as a gas under a low-permeable cap rock (structural trapping) or can dissolve into the ground water (hydrodynamic trapping); it can also react with minerals and organic matter that are dissolved in the brine to form precipitates (mineral trapping). From the perspective of secure, long term storage, mineral trapping has been identified as the most effective mechanism related to subsurface sequestration. Temperature, pressure and salinity are among the primary parameters governing the overall behavior of the process of mineral trapping. In this study, the primary goal is to simulate the behavior of carbon dioxide with an improved model under the conditions of temperature and pressure typical of saline aquifers, i.e. 50 to 100oC and 1-500 bar, respectively. The objective is to determine how the related quantities of molar volume as well as CO2 fugacity change in response to changes in pressure and temperature so that the associated changes in the solubility and the precipitation of carbonates, indicating the rate of CO2 consumption, can be quantified. This study finds that the dissolution rate of anorthite and the rate of precipitation of calcite both rise with the increase in pressure and temperature. The dissolution rate of anorthite has been found to be the rate-limiting process in the sequestration of CO2 and governs the consumption rate of CO2 in the aqueous phase. These results show good agreement with those obtained from experimental work reported in other studies. This study also agrees earlier findings based on relatively less precise models, with respect to the increase in CO2 solubility at higher pressures and a decrease in solubility associated with increasing values of temperature and salinity.
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    Relating pollutant and water quality parameters to landuse in a subwatershed in the Choptank River watershed
    (2010) Nino de Guzman, Gabriela Tejeda; Torrents, Alba; Hapeman, Cathleen J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Agriculture and animal feeding operations have been implicated as sources of water pollution along the Choptank River, an estuary and tributary of the Chesapeake Bay. This survey examined a subwatershed within the Choptank River watershed for impacts of a poultry facility on its adjacent surface water. Water and sediment samples were collected May - October 2009 under mostly baseflow conditions and analyzed for antibiotics, nutrients, heavy metals, and selected bacteria. Of the antibiotics recovered, no significant difference was observed spatially, but a significant difference emerged between spring and fall/winter. For nutrients, the greatest phosphorus concentrations were at the subwatershed outlet (4) and at two branches not containing the poultry house (3 and 5); nitrogen concentrations at sites 2 and 5 were as high as site 4. Arsenic concentrations at 2 were lower than both the low-agriculture (control) site and a site neighboring 3. Bacterial counts in water and sediment remained fairly constant throughout the sampling regime.
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    A TOOL FOR QUANTIFYING THE CARBON FOOTPRINT OF CONSTRUCTION PROJECTS IN THE TRANSPORTATION SECTOR
    (2010) Melanta, Suvish; Hooks, Elise M; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The U.S. construction industry ranks third in the nation in its production of carbon dioxide emissions. Increasing global pressure towards developing emissions reduction strategies is bound to affect the construction industry. The objective of this thesis was to develop a tool to estimate the carbon footprint of construction projects associated with transportation infrastructure. The tool determines emissions from an inventory of equipment, construction processes, and credits efforts to reduce emissions, while incorporating recent and future greenhouse gas (GHG) policies on quantifying emissions. This tool will enable construction companies to identify sources and reduce emissions, while also allowing state agencies to monitor these companies in accordance with GHG laws. The tool was applied to data associated with the construction of the Intercounty Connector, a new roadway that will connect counties in Maryland. Application of the tool to this case study showed its utility and highlighted the need for reduction strategies.