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
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Item Utilizing algal turf scrubbers for bioremediation and bioenergy production(2023) Delp, Danielle Marie; Lansing, Stephanie A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation researched the conversion of algal biomass that was generated as a byproduct of bioremediation by algal turf scrubbers (ATS) into bioenergy via anaerobic digestion. Anaerobic digestion is a bacterial process that converts organic material into bioenergy in the form of biogas that contains methane (CH4), the primary component of natural gas. Bioenergy yield was quantified as the volume of CH4 generated from digestion of the algae in relation to seasonal changes in algal biomass yield, different digester operational parameters, co-digestion of the biomass with more conventional digestion feedstock, and flocculation pre-treatment for dewatering of algae prior to digestion. The first study used a pilot-scale mesophilic digester at the Port of Baltimore (Baltimore, MD, USA) to continuously digest algae from a 122 m2 ATS on the Patapsco River over two years. Biomass generation was significantly correlated to maximum daily air temperature, water temperature, and flow rate in Year 1 but only water flow rate in Year 2. Algae of the taxa Ochrophyta dominated the algal turf, especially the filamentous diatom Melosira sp., in both years. In Year 1 of the study, two anaerobic digestion systems with variable hydraulic retention times (HRT), designated D1 (average HRT 45.0 ± 5.8 days) and D2-D3 (average HRT 61.0 ± 8.1 days) were used to digest the algae. The D1 generated 1090 L CH4 from 2416 L of algae over a 39-day HRT (59.1 ± 8.9 L algae/kg VS), and D2-D3 generated 1170 L CH4 from 2337 L of algae over a 53-day HRT (67.9 ± 11.0 L algae/kg VS). The difference in CH4 yield with two different HRTs was not significant. In Year 2, only the D2-D3 was operated and was modified to test the use of active recirculation and heating to improve digestion efficiency and CH4 yield. The D2-D3 system generated 4000 L of CH4 (163 ± 42 L algae/kg VS) from 3310 L of algae in Year 2. The second study consisted of laboratory-scale biomethane potential tests to test changes in CH4 yield when algae harvested from an Anacostia River (Bladensburg, MD, USA) ATS was co-digested with three wastes (dairy manure, food waste, and poultry litter) at algae:waste loading ratios of at 1:1, 1:2, 1:5, and 1:10 by organic material, or volatile solids (VS), content. The algal biomass was the least efficient substrate at generating CH4 when normalized by both mass VS digested (109 ± 4 mL CH4/g VS) and total mass of substrate digested (0.687 ± 0.025 mL CH4/g substrate). Co-digestion with all three of the wastes at all ratios tested significantly increased CH4 generation efficiency per mass VS compared to only digesting algae. However, the high moisture content of the algae (95.2%) relative to the other co-digestion wastes (29.0-84.6%) significantly decreased CH4 production on a mass basis for the dairy manure, food waste, and poultry litter when algae was added at any loading ratio. A lettuce growth experiment using the effluent of the digestion vessels showed no signs of acute toxicity when any of the diluted (8-fold) digester effluents were applied as fertilizer to the developing plants. The third and final study consisted of flocculation experiments that tested 500-mL of algae using four experimental treatments (FeCl3, electrocoagulation, chitosan, and Bacillus sp. RP 1137) to dewater algae harvested from the Anacostia River ATS and compared to gravity settling as a control. The experimental flocculants successfully increased the total solids (TS) of the ATS algae by 14-291% depending on the treatment, with electrocoagulation being the least effective and bacterial flocculation being the most effective flocculant. All treatments reduced total suspended solids (TSS) in the drained supernatant by >98%. The raw ATS algae and dewatered solids from the settling experiment were then digested for 35-days, with the algae yielding 49.6 ± 3.6 mL of CH4/g VS. The dewatered solids had reduced digestion efficiency by 29.6-71.0% compared to untreated algae. Dewatering pre-treatment increased CH4 yield from the algae when normalized by total g substrate fed to the reactor (1.65 ± 0.12 mL CH4/g substrate) for all treatments except bacteria 1x, however the effect was only significant for solids dewatered with electrocoagulation. The results from the three studies show that temperature drives algal growth patterns in temperate climates, which results in seasonally variable biomass yield from ATS, with a corresponding variability in CH4 production due to inconsistent availability of the algal feedstock. Algae can be co-digested with agricultural and food wastes that are generated year-round to reduce variability in feedstock availability. Thickening and dewatering the algae improves CH4 yield on a mass basis, however the digestion efficiency was reduced. In conclusion, the findings suggest that anaerobic digestion is a viable means of managing the algae harvested from ATS systems with and without co-digestion of the algal biomass.Item Acknowledging Survival: Political Recognition and Indigenous Climate Adaptation in the United States(2021) Cottrell, Clifton; Bierbaum, Rosina; Sprinkle, Robert; Public Policy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Indigenous peoples in the United States are already disproportionately experiencing the impacts of climate change. Closely related to tribal efforts to manage climate effects are historical endeavors to assert indigenous sovereignty and govern tribal lands, but deficiencies in the process used by the U.S. government to acknowledge tribal sovereignty have left hundreds of indigenous communities unrecognized and especially vulnerable to climate harm. My dissertation aims to determine whether a tribe’s recognition status affects its capacity for climate adaptation. To make this determination, I utilize a case study methodology wherein I analyze the circumstances of one non-federally recognized tribe, the Burt Lake Band of Ottawa and Chippewa Indians, in three critical areas related to adaptation and tribal recognition — access to key species and cultural resources, utilization of federal funding opportunities, and participation in climate decision-making. Tribal access to resources is often predicated by historical treaty rights, so I applied a theme identification technique to extrapolate important strategies on easing barriers to resource access and regulatory authority. I then used the themes to compare the likelihood of the Burt Lake Band and nearby federally recognized tribes to maintain connections to key species in the future. I next employed a comparative statutory analysis methodology to differentiate eligibility for non-federally recognized tribes accessing federal funding. I also assessed tribal climate adaptation plans and interviewed tribal climate plan managers on the barriers to successful implementation of adaptation actions. Finally, I developed criteria from a review of global literature on the inclusion of indigenous peoples in adaptation projects to assess participatory opportunities for the Burt Lake Band in state and regional climate governance. My findings show that the Band’s lack of federal recognition inhibits its adaptive capacity to access key cultural resources, federal funding, and climate governance opportunities. However, I also conclude that state and local perceptions of tribal identity could have a greater influence on the adaptation of non-federally recognized tribes, so I recommend that a more inclusive federal recognition system be implemented to avoid the unequal development of indigenous adaptive capacity based on disparate approaches to indigenous affairs by state and local jurisdictions.Item EXPLORING THE TEMPERATURE AND HYDROLOGIC RESPONSE OF TROPICAL OCEANS TO VOLCANIC ERUPTIONS OVER THE LAST 400 YEARS USING CORAL GEOCHEMISTRY(2020) Perez Delgado, Zoraida Paola; Kilbourne, Kelly H.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Volcanic eruptions perturb the Earth’s climate system. Open questions remain about the response of the hydrologic cycle and internal variability. Coral skeletal strontium to calcium ratios (Sr/Ca) and oxygen isotopic ratios (δ18O) record temperature and seawater oxygen isotopic signatures in the oceans, thus climatic perturbations from eruptions maybe recorded in the coral skeletal chemistry. I quantify the temperature and hydrologic response of the tropical climate system to eruptions since 1640 CE based on coral geochemical records. Data from all basins except the central and eastern Pacific show cooling and increases in seawater δ18O within the first three years of an eruption. Statistical significance of identified signals was tested by comparing against non-eruption sections from the records. Analyses with paired Sr/Ca and δ18O illustrate that the number of observations still limits detection of small signals provided by the eruptions.Item The Impact of Cool Roofs in Different Climatic Regions: A Quantitative Empirical Analysis(2014) Petry, Kimberly Johanna; McIntosh, Marla S; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research investigated regional climate differences and weather impacts on the effectiveness of cool roofs. In most US climate zones, cool roofs can reduce energy consumption because they reflect more sunlight and heat than standard roofs. Since temperatures are expected to increase in many regions, cool roofs may offer greater energy and cost savings than currently estimated. Energy consumption by Department of Energy (DOE) Research Laboratory buildings across the US with cool and standard roofs were assessed using metered energy datasets collected from 2003-2013. Statistical tests were conducted to compare differences in energy consumption of buildings between cool and standard roofs at sites in different climatic regions. In order to better understand the effectiveness of cool roof technologies in a future that is expected to become increasingly warmer, data collected from weather stations near each DOE site were used to interpret the potential influences of weather patterns on cool roof energy savings. This research confirmed that cool roofs do reduce energy consumption, especially at sites with warmer summers and milder winters. Regression analyses of energy consumption and temperature data were conducted to identify associations between air temperatures and heating and cooling degree-days with seasonal energy consumption. While the energy consumption of buildings with cool roofs was generally less than buildings with standard roofs, the differences in energy consumption varied depending on building use and building size.Item Variability of terrestrial carbon cycle and its interaction with climate under global warming(2008-08-04) qian, haifeng; Zeng, Ning; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Land-atmosphere carbon exchange makes a significant contribution to the variability of atmospheric CO2 concentration on time scales of seasons to centuries. In this thesis, a terrestrial vegetation and carbon model, VEgetation-Global-Atmosphere-Soil (VEGAS), is used to study the interactions between the terrestrial carbon cycle and climate over a wide-range of temporal and spatial scales. The VEGAS model was first evaluated by comparison with FLUXNET observations. One primary focus of the thesis was to investigate the interannual variability of terrestrial carbon cycle related to climate variations, in particular to El Niño-Southern Oscillation (ENSO). Our analysis indicates that VEGAS can properly capture the response of terrestrial carbon cycle to ENSO: suppression of vegetative activity coupled with enhancement of soil decomposition, due to predominant warmer and drier climate patterns over tropical land associated with El Niño. The combined affect of these forcings causes substantial carbon flux into the atmosphere. A unique aspect of this work is to quantify the direct and indirect effects of soil wetness vegetation activities and consequently on land-atmosphere carbon fluxes. Besides this canonic dominance of the tropical response to ENSO, our modeling study simulated a large carbon flux from the northern mid-latitudes, triggered by the 1998-2002 drought and warming in the region. Our modeling indicates that this drought could be responsible for the abnormally high increase in atmospheric CO2 growth rate (2 ppm/yr) during 2002-2003. We then investigated the carbon cycle-climate feedback in the 21st century. A modest feedback was identified, and the result was incorporated into the Coupled Carbon Cycle Climate Model Inter-comparison Project (C4MIP). Using the fully coupled carbon cycle-climate simulations from C4MIP, we examined the carbon uptake in the Northern High Latitudes poleward of 60˚N (NHL) in the 21st century. C4MIP model results project that the NHL will be a carbon sink by 2100, as CO2 fertilization and warming stimulate vegetation growth, canceling the effect of enhancement of soil decomposition by warming. However, such competing mechanisms may lead to a switch of NHL from a net carbon sink to source after 2100. All these effects are enhanced as a result of positive carbon cycle-climate feedbacks.Item Climate forcing of phytoplankton dynamics in Chesapeake Bay(2006-05-23) Miller, William David; Harding, Jr., Lawrence W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Climate has long been recognized as an important driver of phytoplankton dynamics. In Chesapeake Bay, climate variability is manifest as differences in timing and magnitude of freshwater flow. Interannual differences of freshwater flow influence phytoplankton through effects on light and nutrient distributions. Understanding how climate forces temporal and spatial patterns of phytoplankton biomass (Chla) and primary productivity (PP) is an important area of research as we attempt to predict effects of climate change and nutrient enrichment on estuarine ecosystems. This Dissertation describes climate forcing of Chla and PP using a synoptic climatology to quantify climate variability and ocean color remote sensing to assess phytoplankton variability. I developed a synoptic climatology using surface sea-level pressure data for the eastern United States to characterize regional climate because large-scale climate indices are not strongly expressed in this region. The long time series (1989-2004) of remotely sensed ocean color measurements provided high spatial and temporal resolution that allowed me to resolve interannual differences of Chla and PP. I show that the frequency-of-occurrence of synoptic-scale weather patterns during winter explained 54% of the variance in spring freshwater flow to Chesapeake Bay through interannual differences in precipitation and water storage in the basin as snow and ice. Winter weather patterns were also linked to interannual variability of several characteristics of the spring phytoplankton bloom (timing, position, magnitude) through their effects on precipitation and freshwater flow. Multiple linear regression models of winter weather pattern frequencies on regional Chla explained between 23-89% of the variance of the time series. Climate variability in winter-spring also influenced summer and annual integral production through nutrient loading associated with the spring freshet, explaining between 43-62% of the variance of integral production. Finally, I quantified the effects of Hurricane Isabel on Chesapeake Bay phytoplankton dynamics and showed that event-scale climate perturbations can have significant impacts on ecosystem dynamics as well as seasonal and regional carbon cycling. Together these analyses highlight the importance of climate forcing of Chla and PP in Chesapeake Bay and support predictive models that explain significant amounts of the variance of these important ecosystem properties.Item MULTIVARIATE ERROR COVARIANCE ESTIMATES BY MONTE-CARLO SIMULATION FOR OCEANOGRAPHIC ASSIMILATION STUDIES(2005-08-04) Borovikov, Anna Y; Carton, James A; Rienecker, Michele M; Applied Mathematics and Scientific Computation; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)One of the most difficult aspects of ocean state estimation is the prescription of the model forecast error covariances. Simple covariances are usually prescribed, rarely are cross-covariances between different model variables used. A multivariate model of the forecast error covariance is developed for an Optimal Interpolation (OI) assimilation scheme (MvOI) and compared to simpler Gaussian univariate model (UOI). For the MvOI an estimate of the forecast error statistics is made by Monte Carlo techniques from an ensemble of model forecasts. An important advantage of using an ensemble of ocean states is that it provides a natural way to estimate cross-covariances between the fields of different physical variables constituting the model state vector, at the same time incorporating the model's dynamical and thermodynamical constraints. The robustness of the error covariance estimates as well as the analyses has been established by comparing multiple populations of the ensemble. Temperature observations from the Tropical Atmosphere-Ocean (TAO) array have been assimilated in this study. Data assimilation experiments are validated with a large independent set of subsurface observations of salinity, zonal velocity and temperature. The performance of the UOI and MvOI is similar in temperature. The salinity and velocity fields are greatly improved in the MvOI, as evident from the analyses of the rms differences between these fields and independent observations. The MvOI assimilation is found to improve upon the control (no assimilation) run in generating water masses with properties close to those observed, while the UOI fails to maintain the temperature-salinity relationship. The feasibility of representing a reduced error subspace through empirical orthogonal functions (EOFs) is discussed and a method proposed to substitute the local noise-like variability by a simple model. While computationally efficient, this method produces results only slightly inferior to the MvOI with the full set of EOFs. An assimilation scheme with a multivariate forecast error model has the capability to simultaneously process observations of different types. This was tested using temperature data and synthetic salinity observations. The resulting subsurface structures both in temperature and salinity are the closest to the observed, while the currents structure is maintained in dynamically consistent manner.Item THE RELATIONSHIP OF PERCEPTIONS OF CAMPUS CLIMATE AND SOCIAL SUPPORT TO ADJUSTMENT TO COLLEGE FOR LATINA SORORITY AND NON-SORORITY MEMBERS(2005-05-27) Garcia, Gina Ann; McEwen, Marylu K; Counseling and Personnel Services; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study was to explore whether there were differences in adjustment to college for Latina college students who are members of a Latina sorority and those who are non-members. A second purpose was to examine whether perceptions of campus climate and social support predicted academic, social, personal emotional, goal commitment-institutional, and overall adjustment to college. Using a web-based survey, the University Environment Scale (Gloria & Kurpius, 1996), social support scales (Schneider & Ward, 2003), and Student Adaptation to College Questionnaire (Baker & Siryk, 1984) were used to collect data. Respondents included 314 Latina college students (183 members, 131 non-members) from a variety of institutions nationwide. Latina sorority members had significantly higher levels of social adjustment and goal commitment-institutional adjustment than non-members. Additionally, perceptions of campus climate and social support were significant predictors of adjustment for both groups, with 21%-64% variance explained for each form of adjustment.Item Understanding State Goal Orientation: Leadership and Work-Group Climate as Key Antecedents(2005-01-26) Dragoni, Lisa; Stevens, Cynthia K.; Tesluk, Paul E.; Management and Organization; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research attends to a broad range of practically significant employee achievement goals and provides insight into how to enhance individual-level performance by examining the antecedents to individual-level state goal orientation in organizational work groups. State goal orientation is defined here as a temporary achievement goal, and it is theorized that leadership and work group climate processes parallel each dimension of state goal orientation to cue and ultimately induce the corresponding achievement goal among individual work group members. The leader's achievement priority is argued to drive the formation of work group climate consistent with this priority. The resulting work group climate signals and compels group members to adopt the ascribed form of state goal orientation. The quality of the leader-member exchange (LMX) relationship is viewed as a means to internalize cues from the work group climate in the emergence of state goal orientation. Results from experimental and field studies provide evidence that (1) leadership and climate perceptions are related to their parallel form of state goal orientation, (2) the relation between individual perceptions of a climate for learning and state learning goal orientation is stronger when group members enjoy higher quality exchange relationships with their leader, and (3) state goal orientation may be validly and reliably assessed using the measure created especially for this research.Item The Effect of Organizational Climate on the Attribution to Discrimination Process(2004-04-12) Leslie, Lisa Michelle; Gelfand, Michele J; Stangor, Charles; PsychologyResearch on the multi-stage attribution to discrimination process (construct accessibility, perceiving, and reporting of discrimination) focuses on individual difference antecedents and tends to examine one stage in each study (e.g. Major et al., 2002; Stangor, Sechrist, & Swim, 1999; Swim & Hyers, 1999). The current study extends research on this process by examining the interactive effect of individual differences and organizational climate on all three stages of the attribution to discrimination process in an organizational simulation study. Findings indicate that Climate for Intolerance for Discrimination interacts with individual based sensitivity to sexism to predict perceptions of discrimination. Furthermore, perceptions of discrimination fully mediate the relationship between the climate by sensitivity interaction and reporting of discrimination to the organization.