Browsing by Author "Griffin, Robert"

Now showing 1 - 7 of 7
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    Characterization of Atmospheric Nitrogen Chemistry and the Formation/ Evolution of Particulate Matter in Houston, TX
    (2015-12-04) Leong, Yu Jun; Griffin, Robert; Cohan, Daniel; Biswal, Sibani L
    This thesis covers laboratory experiments to study the homogeneous reduction of nitric acid (HNO₃) to nitrous acid (HONO) in the presence of volatile organic compounds that are surrogates for those emitted by motor vehicles. The results presented in this study focus on the impact of environmental variables on the rate of formation of HONO in this process. The homogeneous conversion of HNO₃ to HONO has significant atmospheric implications due to the “renoxification” of less reactive HNO₃ into more reactive HONO. Consecutively, this thesis describes particulate matter (PM) data collected from a month-long (September 2013) field project in Houston, TX. A mobile laboratory containing state-of-the-art PM instrumentation and auxiliary measurements was deployed. The main focus for the thesis work was to utilize this dataset to better characterize PM pollution in the city of Houston. This was achieved by several analysis approaches including cluster analysis, back-trajectory analysis, and principal component analysis to describe spatial and temporal variations in submicron PM in the Houston region. Finally, this work describes the use of a statistical source apportionment technique, positive matrix factorization, on the field dataset to apportion important constituents of atmospheric aerosols in Houston. This technique allowed the apportionment of four organic aerosol factors, two of which were associated with organic nitrates from biogenic sources. Submicron PM plume events from on-road, industrial, and biomass burning sources in Houston also were chemically characterized. Because sources of PM pollution are still poorly understood, particularly in the highly industrial and urban city of Houston, the results from this thesis will advance PM modeling capabilities and allow improved PM control strategies in polluted urban areas similar to Houston.
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    Implementing and Improved Soil NOx Parameterization in the Community Multiscale Air Quality Model: Implications for Air Pollution
    (2014-12-05) Lash, Benjamin; Cohan, Daniel S; Griffin, Robert; Masiello, Caroline
    Soil NO emissions are critical to accurate atmospheric simulations which inform decisions to protect human health. Several studies indicate that the scheme, Yienger and Levy 1995 (YL95), underestimates soil NO emissions by a significant amount. The Berkeley Dalhousie Soil NOx Parameterization (BDSNP) updates soil NO emissions to be more consistent with satellite measurements. This work implements the BDSNP algorithm into CMAQ, adapting it to a 12km grid and comparing the resulting ozone, particulate, and other pollutants with results from the current YL95 algorithm for 2005 satellite data. Results show that summer NO emissions over the US double during the day, and in some places soil NO exceeds industrial sources. A comparison with satellite data, however, does not show strong evidence of the YL underestimation, contrary to other published results.
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    Improvements to the Characterization of Hurricane Flooding with Advanced Statistical and Numerical Modeling
    (2017-12-19) Bass, Benjamin; Bedient, Philip; Griffin, Robert
    Hurricanes have historically and continue to result in some of the most devastating natural disasters. Despite a wealth of research efforts since the active 2005 hurricane season (i.e. Katrina, Rita, Wilma), key questions related to hurricane flood characterization, mitigation, forecasts, and frequency remain under-explored. This dissertation addresses such research topics by combining several numerical models with hindcast, deterministic, and probabilistic methodologies to represent multiple hurricane flood hazards, including storm surge, rainfall-runoff, and interactions between these two sources of flooding (combined flooding). This thesis begins with the first numerical analysis of the performance and sensitivity of different hurricane storm surge indices, or simple parametric descriptors of hurricane characteristics, and their ability to represent a hurricane’s storm surge response. After Katrina (2005) several surge indices were proposed to replace the category-based Saffir-Simpson index, but these surge indices were either not evaluated or their performance relative to one another was determined inconclusive due to limited observational data. For this, and other projects in this thesis, the storm surge response of hurricanes was evaluated using the tightly coupled ADvanced CIRCulation (ADCIRC) and Simulating WAves Nearshore (SWAN) model (ADCIRC+SWAN). Findings from this research demonstrate the performance and sensitivity of different surge indices and can help guide the replacement of Saffir-Simpson categories with an improved hurricane storm surge index. In the second study of this thesis, storm surge dynamics are characterized in a complex bay environment to understand how variations in storm and environmental factors, including sea level rise and the potential erosion of barrier islands, influence flow dynamics across the various tidal inlets and barrier islands that make up Galveston Bay’s (the Bay’s) coastline. This research provides useful insight regarding the regional flood vulnerability of the Houston-Galveston region and how this flood vulnerability can effectively be reduced by focusing surge mitigation along specific sections of the Bay’s coastline. The third study in this thesis demonstrates that while a coastal barrier can prevent flood impacts from oceanic storm surge, significant storm surge can still develop within Galveston Bay itself, suggesting the additional need for multiple lines of defense strategies. This study proceeds to evaluate the hydrodynamic performance of several regional surge mitigation strategies, including designs that protect from oceanic storm surge as well as local surge that can develop within Galveston Bay itself. Analyses in this study goes beyond the typical 100-yr rule of thumb design by evaluating the performance of different strategies for several return period events under current as well as future sea level conditions. The final study of this thesis evaluates combined flooding in coastal watersheds due to rainfall-runoff associated with hurricanes and its interactions with storm surge. Such analysis is crucial given that rainfall associated flooding is still not represented in probabilistic forecasting and frequency (i.e. 100-yr floodplain) products despite causing ~27% of human fatalities during hurricane events. To fill this information gap, a rapid hurricane flood prediction system was developed to represent the combined flood response from hurricanes. The utility of this combined flood prediction system was then demonstrated by improving upon probabilistic hurricane flood forecasting and frequency products. In this thesis, numerical flood analysis was performed in coastal watersheds, a bay, and the open coast. By characterizing, forecasting, and evaluating different strategies to protect against hurricanes, the author hopes to not only advance the current state of hurricane science, but to additionally provide practical insight and tools to increase coastal resiliency.
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    Improving and Developing Statistical Methods for Analyzing Air Pollution Measurements
    (2022-04-19) Actkinson, Blake; Griffin, Robert
    With the advent of a big data revolution in air pollution research comes a necessity for refining existing statistical techniques and developing new ones that are robust, scalable, and informative. This work discusses the development of novel statistical methods applied to air pollution and can be broken into two parts: improving an existing method to analyze air pollution measurements taken at stationary monitors and developing new methods to analyze novel measurements taken with a mobile platform. In the first main chapter of this thesis, Dynamic Principal Component Analysis (DPCA) is discussed as an alternative to Principal Component Analysis (PCA) for analyzing time-dependent relationships between air pollutant variables measured at stationary monitors. DPCA is shown to offer several advantages over PCA, in that it generates a set of statistics which are time dependent and uncovers a wealth of information not readily apparent in a conventional static application. The second part of this work discusses development of new statistical methods to analyze a burgeoning and increasingly important method of measuring air pollution, which is through mobile monitoring. Mobile monitoring offers excellent spatial coverage at the expense of temporal coverage, making many conventional statistical techniques frequently employed by the atmospheric sciences community ill-suited for analysis of these measurements. Subsequent chapters discuss mobile monitoring as a measurement strategy, a novel algorithm to derive and quantify the background in mobile monitoring measurements, and another novel algorithm to identify and analyze detected plumes in time series. Results from these algorithms showcase the power mobile measurements have to inform stakeholders about the spatial variability of air pollution not obvious through the use of stationary monitors alone. It is hoped that through the refinement and development of these techniques and others that an important and exciting era of air pollution research can be ushered and its long-term mysteries solved.
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    Municipal Solid Waste as a Viable Alternative Fuel in the U.S.A.
    (2014-11-25) McPhail, Ana; Griffin, Robert; Alvarez, Pedro J.J.; El-Halwagi, Mahmoud; Medlock, Kenneth; Lin, Cynthia
    This thesis work evaluates whether municipal solid waste (MSW) may be a viable alternative and renewable fuel source within the United States. The framework for achieving this objective is split into two large, distinct studies. The first study discerns the relationship between MSW composition (including varying moisture), air pollutant concentrations and associated heating values. Models included AspenPlus® software for the deterministic simulation modeling of thermodynamic and pollution information, and U.S. EPA models WAR and WARM to determine the potential environmental impacts (PEI) and greenhouse gas emission equivalencies, respectively, for each MSW scenario. An economic profitability analysis was also conducted. This study focused on five high impact air combustion products: SO2, CO, CO2, NO and NO2. Results show that flue gas concentrations (and therefore PEI) depend on the composition and moisture of the MSW, in addition to the MSW to coal ratio. The recycled paper and composted organics scenario gave the lowest heating value (8,251 MBtu/lb). Approximate ranges for the WAR results (PEI/hr) are 7,410 to 7,663 for NO, 4 to 8 for NO2, 18 to 105 for CO, 30 to 46 for CO2, and 89 to 2,152 for SO2. WARM results show lower net CO2 emission equivalents to landfill MSW with reduced paper and organics, while combustion is preferred for MSW with paper, organics, or plastics reduction. Reduction in pollutant concentrations yielded a reduction in profit between ~20-30%. There were savings associated with emission costs by using MSW in lieu of coal: up to ~3.3% for NO, ~20-47% for NO2, and ~95% for SO2. In summary, the measurable impact MSW composition and moisture had on pollutant concentration, heating value, and economic parameters were important. The second study is used to link the information gathered in the first study with legislative actions locally and abroad. In this study, four unique scenarios and one aggregate scenario varied subsidies, health impacts, fines, energy credits and fiscal policy data and distributions using Monte Carlo analysis to evaluate and foster policy initiatives while determining the economic feasibility of MSW as a renewable fuel for municipalities. Results show the supply stack for electricity generation uses the cheapest fuel (coal), then the second cheapest (natural gas) until demand is met or more fuels are needed. The social marginal cost (SMC) without considering further policy changes yields costs of $0.165/kWh for coal, $0.209/kWh for NG and $0.349/kWh for MSW. Implementing policy changes for internalizing the health impacts currently paid for by the community and the aggregate impact of all scenarios would level the economic playing field for MSW, providing lower SMC’s of $0.327/kWh for MSW in both cases, and higher SMC’s for coal and NG in other scenarios such that the order of the supply stack changes. This work advances the fundamental understanding of the economic limitations and advantages, and the policies needed to foster further proliferation of MSW as a fuel.
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    Simulation of the Atmospheric Fate and Transport of Chemicals from Aboveground Storage Tank Leakage Post Severe Storms
    (2018-04-19) Bi, Shiyang; Griffin, Robert
    Hurricanes can damage the industrial infrastructure containing hazardous chemicals, which causes widespread environmental pollution in both water and air systems. To estimate the regional atmospheric concentration of evaporated spill material, as well as of secondary pollutants ozone (O3) and secondary organic aerosol (SOA) from petrochemicals released from aboveground storage tanks (AST) leakage post hurricanes, a Lagrangian particle dispersion model associated with a detailed non-linear zero-dimensional Eulerian chemistry model was developed. The developed model couples the EFDC-SS water quality model for simulating the transport of spill material along the storm surge, the FLEXPART model for simulating the physical transport of evaporated spill material, The Master chemical mechanism for simulating the gas-phase chemistry, Volatility basis set approach for simulating the SOA formation, and the resistance model for simulating dry deposition processes. Five runs were conducted to evaluated various hurricane scenarios (Hurricane Harvey and Hurricane Ike), combined with different types of spill materials (oils and organic solvents) released under different cloud conditions. Results show that the downwind plumes of oils with slower evaporation rates are predicted to cover a broader region while the organic solvent plumes are more concentrated and move along the wind trajectory. It is also determined that the downwind plume concentration is predicted to be higher under lower planetary boundary (PBL) height and stable PBL conditions during the night. Additionally, results show that O3 and SOA formation is significant within the downwind plume and largely depends on the solar radiation intensity and the types of spill materials. This research helps to highlight the vulnerability of downwind regions to evaporated spill materials and lends insight to secondary pollutant formation within the downwind plume.
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    The impacts of regional shipping emissions on coastal submicron aerosols near Houston, TX
    (2018-04-20) Schulze, Ben Christopher; Griffin, Robert
    This thesis describes the analysis of coastal field measurements of atmospheric aerosols and trace gases near Houston, TX, aimed at investigating the influence of regional shipping emissions on coastal aerosol mass loadings, composition, and formation mechanisms. Data collection utilized a mobile laboratory containing both particulate matter and trace gas instrumentation. Positive matrix factorization was used to apportion measured organic aerosol into five distinct factors. Further analysis suggests that one factor is associated with emissions from shipping vessels in the Gulf of Mexico. Measured inorganic aerosol was apportioned between anthropogenic and biogenic sources using published biogenic ratios of methanesulfonic acid and non-sea-salt sulfate, revealing that the majority of submicron inorganic aerosol produced over the Gulf of Mexico is anthropogenic. Subsequent analysis using the weighted potential source contribution function and published emissions inventories supports the attribution of this anthropogenic aerosol to commercial shipping vessels. Backward trajectory analysis suggests that shipping vessel emissions may influence organic aerosol composition, potentially leading to altered physical characteristics such as the capacity to absorb water. Finally, zero-dimensional modeling suggests that inland advection of anthropogenic marine aerosol may promote secondary organic aerosol formation in the aqueous phase over the Houston region. The results of this thesis highlight the continuing influence of shipping emissions on coastal aerosol characteristics near Houston, TX, and provide support for further emission regulations.