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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    PREVENTION AND TREATMENT OF PERSISTENT ORGANIC POLLUTANTS IN STORMWATER AND SEDIMENT
    (2023) Yuan, Chen; Kjellerup, Birthe V; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Polycyclic aromatic hydrocarbons (PAHs) and Polychlorinated biphenyls (PCBs) are two groups of persistent organic pollutants (POPs) with toxicity, carcinogenicity, and teratogenicity. Those compounds are harmful to human health and wildlife. Stormwater is one of the important sources of PAHs and PCBs to aquatic environments. Stormwater control measures (SCMs) have already been used to remove PAHs and PCBs from stormwater, however traditional SCMs can remove PAHs and PCBs in the particle phase, but there still are dissolved PAHs and PCBs in the outflow of SCMs. This study focused on reducing the influence of PAHs and PCBs in stormwater on the environment by 1) improve the treatment performance by adding a polishing treatment procedure after traditional SCMs, and remove the PAHs and PCBs accumulated in the polishing treatment media by bioaugmentation of Pseudomonas putida ATCC 17484 and Paraburkholderia xenovorans LB400 and 2) dechlorination of PCBs in the sediment of aquatic environments by biofilm Dehalobium chlorocoercia DF1 inoculum. The results of polishing treatment showed that all black carbon materials, namely biochar, granular activated carbon (GAC), and regenerated GAC (RAC), were effective to remove dissolved PAHs with removal > 95%. However, all materials had lower removal efficiency on PCBs with removal > 84%, By the comparation of cost and lifetime under the condition that 50% polishing media are used in the polishing treatment facility. RAC which has a lifetime>147 years based on the precipitation of Maryland and Washington and cost <3.79 $-m3-yr-1, was the best material for polishing treatment. Results of treatment train with a traditional SCM media column and polishing treatment column indicated that average removal of PAHs can be improved from 94.56% of BSM columns to 99.61% of polishing treatment columns, and removal of PCBs can be improved from 84.61% to 95.16%. Results of bioaugmentation of polishing treatment media showed no biodegradation took place in the mesocosms with polishing media. However, the liquid mesocosms showed P.putida degraded 97.9% of pyrene. The bacteria colony on plates after the biodegradation experiment showed that there were less P.putida and P.xenovorans colony of polishing media mesocosms than liquid mesocosms. Therefore, the limitation of biodegradation of polishing media mesocosms may cause by the limited bioavailability and less active inoculated bacteria. The results of dechlorination by Dehalobium chlorocoercia DF1 biofilm shows that there were native bacteria, such as Gemmatimonadetes, Actinobacteria, Proteobacteria and Firmicutes in the sediment that can dechlorinate PCBs. The three treated mesocosm groups (addition of biochar, bioaugmentation with DF1 biofilm and liquid DF1 culture) all can improve dechlorination, of 28.09%, 21.30%, and 17.10%, respectively. Those three groups had dechlorination extent higher than negative control (4.60%), and abiotic control (-1.02%). The microbial community analysis indicated that biofilm inoculation improved abundance of DF1 and had a more stable influence on the community than liquid inoculation. Overall, biofilm inoculation and addition of biochar dechlorinate PCBs in sediment efficiently, and polishing treatment is an efficient approach to improve traditional SCMs, while treating the polishing media with bioaugmentation need further study.
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    ENHANCING BIOREMEDIATION OF TCE-CONTAMINATED GROUNDWATER AT THE BEAVERDAM ROAD LANDFILL
    (2022) Saffari Ghandehari, Shahrzad; Kjellerup, Birthe; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Trichloroethene (TCE) is one of the most frequently found groundwater contaminants, thus remediating TCE-contaminated groundwater bodies is crucial in providing safe drinking water to people around the world. However, due to the resistance of its intermediates to degradation and their toxicity, TCE bioremediation is still challenging. Years after the installation of a permeable reactive barrier (PRB), the levels of toxic TCE dechlorination intermediates had increased downgradient from the PRB, indicating the need for actions to prevent the contaminated water from reaching a stream nearby. A review of the reports and monitoring results showed that low groundwater residence time and low pH levels were contributing to the inefficiency of the PRB. A trench was purposed to be installed upgradient from this PRB to increase the groundwater contact time with the microorganisms and organic carbon content of the soil using wastewater biosolids, limestone, and biochar to increase the buffer capacity of the soil and the sorption of TCE to the soil. Bench-scale studies were conducted with biosolids and limestone to observe the effect of the biosolids microbial population on a TCE-dechlorinating mixed microbial community. Both dechlorinating bacteria and methanogens use hydrogen in their metabolism and potentially can compete with each other. While biosolids-limestone reactors produced significantly higher concentrations of methane, the activity of methane-producing microorganisms did not adversely affect TCE dechlorination. Furthermore, the characterization of the microbial community of the reactors indicated the positive effect of biosolids. Based on the results from this study, the trench was installed in January 2020 at the site. The sampling and monitoring results nine months after its installation indicated that the trench filling material had positively affected the soil microbial community and decreased the TCE levels downgradient from the trench. To further characterize the microbial community of the site, passive samplers using biochar were installed upgradient and inside the PRB to compare the activity of the dechlorinating bacteria. It was shown that the PRB microbial population was capable of complete dechlorination of TCE, while dechlorinating bacteria detected in the upgradient samples were not active, resulting in the different TCE concentrations observed in these locations. Overall, the study showed that biosolids can be used as an amendment in the TCE bioremediation purposes. Future work should focus on further monitoring the effect of the treatments, applied in this site.
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    Evaluation of organic inputs for reducing dollar spot disease on cool-season turfgrasses
    (2018) Beckley, Cody James; Roberts, Joseph A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Lolium perenne, Poa annua, and Agrostis stolonifera are turfgrass species commonly grown on golf course fairways; however, they are susceptible to dollar spot (Clarireedia spp.). Field studies were conduction to assess: 1) the effects of organic fertilizer treatments and fungicide programs on dollar spot severity; and 2) the impact of organic amendments on dollar spot severity and residual fungicide efficacy. Alternating applications of organic and conventional fungicides reduced seasonal dollar spot severity to the same degree as conventional fungicides. Dollar spot was more severe in Lolium perenne and Poa annua treated with organic fungicides. On A. stolonifera, organic biosolids compost, biochar, and vermicompost amendments suppressed dollar spot to the same degree as conventional fertilizer in year one of the trial, while dollar spot was more severe on A. stolonifera fertilized with organic biosolids compost in year two. Fertilizer treatments had no effect on residual fungicide efficacy on A. stolonifera.
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    Evaluation of Biochar Applications and Irrigation as Climate Change Adaptation Options for Agricultural Systems
    (2014) Lychuk, Taras; Hill, Robert L; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Environmental Policy Integrated Climate (EPIC) model was updated with algorithms to determine the effects of biochar applications on crop yields and selected soil properties. EPIC was validated using the results of a 4-yr field experiment performed on an Amazonian Oxisol amended with biochar. Simulations were conducted for 20-yr into the future and predicted increased values of soil cation exchange capacity, pH, soil C content, and decreased soil bulk density values after biochar applications. EPIC was then used to evaluate climate change impacts and effectiveness of annual biochar applications and irrigation as adaptation options on yields of C3 and C4 crops from representative farms in 10 Southeastern US states. Simulations were conducted for 1979- 2009 historical baseline climate data and 2038-2068 time periods using four regional climate models (RCM). Future corn (Zea mays L.) yields initially increased, but corn and soybean (Glycine max L.) yields had decreased by 2068. Future C4 crops generally produced higher yields compared to the historical yields of C4 crops. Historical baseline yields of C3 crops and future C3 crop yields were not significantly different. Biochar amendments had no effects on yields and in some cases resulted in significant yield decreases. Irrigation caused increases in corn yields, but not for soybean yields. Irrigation did result in increased C3 and C4 crop yields for some farms that were typically in drier areas. Further EPIC simulations were conducted to estimate the effects of climate change impacts and adaptations on microbial respiration, soil C content, and nitrate losses in runoff and leachate. Microbial respiration was higher under C4 crops than under C3 crops. Biochar amendments increased microbial respiration, although the relative relationship of C4>C3 microbial respiration was maintained. Nitrate losses were significantly higher in the future and followed a C3>C4 pattern. The greatest nitrate losses were observed under C3 crops with even greater losses due to irrigation. Biochar amendments resulted in reduced losses for nitrate in leachate, but not in runoff. C sequestration increased under C4 crops and biochar applications. Under some RCM weather scenarios, biochar applications and irrigation are promising adaptation strategies for agriculture in the Southeastern US.