College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item High Quality Biosolids: Assessment of Nitrogen Mineralization and Potential for Improving Highway Soils(2019) Zhu, Chenglin; Felton, Gary K; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids production is increasing with increase in human population. Over the years, the quality of biosolids has been improving with the upgrading of most wastewater treatment plants (WWTP) as dictated by a need to meet discharge limits in receiving water bodies. Applying biosolids to agricultural soils to improve crop production has been practiced for decades. With increased regulation on land application in agricultural lands, biosolids industry has been exploring ways to use biosolids in specific situations such as highway roadside soils to improve soil properties. Roadside soils are known to be compacted and contaminated due to vehicular traffic and typically have low organic matter and nutrients. The objective of this study was to investigate the efficacy of high quality biosolids (i.e. Bloom) to improve soil physical and chemical properties. Results showed that Bloom and its mixture can significantly improve soil bulk density and hydraulic conductivity. Bloom-amended soils had a higher nitrogen mineralization rate than the control (2.45 times faster in simulated roadside soil and 1.21 times faster in agricultural soil) and compost amended soil. Further, soils amended with cured Bloom had relatively slower N mineralization than those applied with uncured Bloom since the curing process will decrease organic matter (OM) content and facilitate the loss of N as ammonium. The take home message is that bloom is more effective than inorganic fertilizer in terms of improving soil physical properties for roadside soils and bloom mixed with sand and sawdust is more effective than pure bloom. Bloom addition can significantly increase soil organic nitrogen mineralization. Further study and analysis will be needed to conclude on the effect of deer compost on soil physical properties and the mineralization rate of Orgro amended soil.Item INCREASING EFFICIENCY AND SUSTAINABILITY OF WASTE-TO-ENERGY SYSTEMS USING BIOCHAR FOR HYDROGEN SULFIDE CONTROL AND LIFE CYCLE ASSESSMENT(2019) Choudhury, Abhinav; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The research aim was to increase energy production efficiency and reduce the environmental impacts of waste-to-energy technologies, specifically anaerobic digestion (AD) of dairy manure (DM) and combustion of poultry litter (PL). The first objective was co-digestion of DM with gummy vitamin waste (GVW) to increase methane (CH4) yield. The GVW co-digestion treatments significantly increased CH4 yield by 126% - 151% compared to DM-only treatment and significantly decreased the H2S concentration in the biogas by 66% - 83% compared to DM-only. The second objective was understanding the effect of hydrogen sulfide (H2S) scrubber management, operation, and maintenance parameters on H2S removal efficiency. Even though the capital and operating costs for the two H2S scrubbing systems in this study were low (< $1500/year), they showed ineffective performance due to insufficient air injection, substitution of proprietary iron oxide-based H2S adsorbents for cheaper alternatives, and the lack of dedicated operators. The third objective was adsorption of H2S using Fe-impregnated biochar as a substitute for activated carbon (AC). Fe-impregnation of biochar led to a 4.3-fold increase in the H2S adsorption capacity compared to AC. When compared to unimpregnated biochars, Fe-impregnation led to an average 3.2-fold increase in the H2S adsorption capacity. The fourth objective was in-situ use of biochar in AD to remove H2S. In-situ biochar addition at the highest dose (1.82 g biochar/g manure total solids (TS)) resulted in an average H2S removal efficiency of 91.2%. Biochar particle size had no significant effect on H2S reduction. In-situ addition of Fe-impregnated biochar resulted in an average H2S removal efficiency of 98.5%. The fifth objective was a life cycle assessment (LCA) of a PL fluidized bed combustion (FBC) system. The LCA assessment showed that heating poultry houses using heat obtained from the combustion of PL in the FBC system had 32% lower climate change potential (CCP) compared to use of propane for heating poultry houses. However, analyzing the FBC system under a net positive electrical output scenario resulted in 66% less impact on CCP and a 48 – 98% reduction in environmental impacts compared to the previous scenario with net electricity input.Item BLOOM BIOSOLIDS: WHAT IS THEIR MICROBIAL COMMUNITY AND HOW DO THEY AFFECT SOIL AND PLANT HEALTH?(2019) Baballari, Eni; Yarwood, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids are rich in nutrients and organic matter, and are known to improve and maintain productive soils and stimulate plant growth. D.C. Water’s new Class A biosolids product, Bloom, was evaluated for its impact on plant and soil health. Using molecular tools, Bloom was examined for the presence of functional genes that would indicate the presence of microbes capable of improving plant growth (i.e.nitrifiers, N- fixers). Using greenhouse and laboratory experiments, we determined Bloom’s effect on plant growth, carbon and nitrogen cycling. Bloom has both nitrifying and N-fixing microbes, but their gene numbers vary depending on the stage of production. We show that plants, such as cucumber and tomato, grown in soil amended with Bloom produce more leaves and stems and have higher aboveground biomass, and soybeans produced more bean pods. Lastly, we found that N-mineralization is higher in soil amended with Bloom, even after one growing season, providing increased nutrients.Item Nitrogen cycling by grass-brassica mixtures in the Mid-Atlantic(2019) Gaimaro, Joshua Ruben; Tully, Kate; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mixtures of cover crop species may be more effective than monocultures at internal nutrient cycling due to their ability to occupy different niches. Our study investigates nitrogen (N) cycling of radish (Raphanus sativus L.) and rye (Secale cereal L.) in monocultures and mixtures compared to a no cover crop control. The study was established on fine-textured soils near Laurel, MD where we estimated N leaching losses, quantified mineral soil N (to 60 cm), and cover crop biomass N for two years. Forage radish suppressed estimated N leaching in the fall, while cereal rye suppressed estimated N leaching in the spring. In this study, growing radish in a mixture with rye decreased the risk of N leaching losses and enhanced N cycling due to the difference in timing of N uptake and release. Our research indicates that grass-brassica mixtures are a flexible management tool for mitigating N leaching in the Mid-Atlantic.Item SOIL ORGANIC CARBON IN MID-ATLANTIC REGION FOREST SOILS: STOCKS AND VERTICAL DISTRIBUTION(2019) Colopietro, Daniel John; Weil, Ray R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soil contains the largest terrestrial pool of organic carbon (Boschi et al., 2018) and temperate forest soils have been a major sink for atmospheric carbon; however, determining the size of the soil organic carbon stock can be problematic. Sampling practices vary for sampling depth, and determining the density of the soil. The aforementioned standard practices need to be revised if the size of SOC stocks are to be accurately quantified, to establish a global SOC baseline. A soil monitoring of 414 forested sites within 11 national parks in the National Capital Region (Schmit, 2014) was conducted over 10 years. Samples were collected from the leaf litter and each soil horizon to 1 meter depth. Soil bulk density (Db) was determined by the core method for the A horizons, and proxy Db values were investigated for the subsoil. The vertical distribution of SOC concentration and stocks were evaluated with respect to soil order, physiographic region/landform, drainage class and parent material.Item Quantifying the Ecosystem Metabolism of a Tidal Estuary as a Consequence of Aeration(2019) Gotthardt, Zachary; Harris, Lora A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As anthropogenic activity affects shallow estuaries it is imperative to quantify how these systems respond to changing conditions. Ecosystem metabolism is an integrative, metric to measure how ecosystems change, and can act as the focus of comparative experiments. We leveraged an aeration system, to examine the ecosystem metabolism of the estuary through comparative experiments. The aeration system allows us to study a normoxic, eutrophic ecosystem. Chapter 1 explains the causes and effects of eutrophication, with an emphasis on the connection between hypoxia and eutrophication. In chapter 2, we describe an experiment focused on quantifying the ecosystem metabolism in a tidal, eutrophic estuary where engineered aeration has been operational since the 1980s. The aeration system provides an ideal site for addressing some of the difficulties inherent to studying eutrophication. In our experiments, we observed evidence of chemoautotrophy when the aerators were operational. Bottle methods and open water methods provided conflicting results.Item Spatio-temporal mechanisms of urban mosquito coexistence in Baltimore, MD(2019) Saunders, Megan Elizabeth Maria; Leisnham, Paul T.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding the interactions governing species distributions and community structure are of fundamental ecological importance. Mosquitoes that utilize container habitats at their larval stage usually engage in strong competition and competitive exclusion is expected; however, numerous container-utilizing mosquito species co-occur in the same individual container habitats and regionally coexist. I investigated spatial and temporal mechanisms governing the distributions and abundances of the competitively superior invasive Aedes albopictus and resident Culex spp. mosquitoes in four neighborhoods with varying socioeconomic status in Baltimore, Maryland. Specifically, I investigated if the findings from both field surveys and field and laboratory experiments were consistent with four spatial and temporal hypotheses for species coexistence that act at different scales: spatial partitioning among neighborhoods and blocks, seasonal condition-specific competition, aggregation among individual container habitats, and priority colonization effects within individual containers. I found modest but important evidence for all hypotheses that could each facilitate Culex spp. coexistence with Ae. albopictus. I found clear neighborhood effects, with low SES neighborhoods supporting higher abundances of mosquitoes than high SES neighborhoods overall, but with the highest abundances of Ae. albopictus in low SES neighborhoods and Culex spp. being more variable among neighborhoods. Culex spp. abundances were higher in the early summer compared to mid-summer peaks in abundance for Ae. albopictus. Laboratory competition trials showed increased aggregation of Ae. albopictus had a slight positive effect on Culex spp. population performance, and aggregation conditions sufficient for coexistence among experimentally placed ovitraps and negative associations of Aedes and Culex genera in resident containers in the field. Lastly, I found that priority colonization of a container leads to stronger population performance for both species, and that resource availability seems to affect Culex spp. more than competition. The results of my dissertation have revealed the role of several ecological mechanisms that may facilitate the regional coexistence of Culex spp. with Ae. albopictus and is among the first bodies of work to do so. Due to their roles in the transmission of human pathogens, future examination of other spatial and temporal mechanisms of coexistence between Ae. albopictus and resident Culex spp. is warranted.Item Survival and biochemical health indicators of Elliptio complanata deployed in Anacostia River tributaries for monitoring of persistent organic contaminants(2019) Harrison, Rachel Marie; Yonkos, Lance T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Anacostia River is one of three regions-of-concern in the Chesapeake Bay Watershed. Persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides are known to accumulate in sediment and biota within portions of the Anacostia system, but on-going contaminant sources are poorly understood. The current study investigates relative contaminant burdens in the freshwater mussel Elliptio complanata deployed in six non-tidal Anacostia tributaries and an out-of-system reference site. Mussels acquire contaminants during feeding and are a useful tool for monitoring POPs transporting through the system. Mussels were effective at identifying sites with high contaminant loads. The study also investigates the suitability of Anacostia tributaries for reintroduction of E. complanata to increase benthic community diversity and potentially improve water quality. Survival and growth during deployment was very good for both sampling seasons. Biochemical health parameters of deployed mussels suggest that conditions may be suitable for mussel reintroduction.Item URBAN WATER SUPPLY PLANNING UNDER CLIMATE AND DEMAND GROWTH UNCERTAINTIES: A FRAMEWORK FOR IMPROVING SYSTEM RESILIENCE(2019) Yhap, Krystal Gayle; Negahban-Azar, Masoud; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urban areas around the world are facing increased challenges in consistently and reliably providing water services. Rapid urbanization, climate change, and the disjointed management of water distribution systems reveal the need for the creation of holistic management solutions. San Francisco Public Utilities Commission (SFPUC) is considering alternative water supply options to improve the reliability of San Francisco’s water resource, which provided a case study for this research. This research proposes an alternative planning tool used for systematic urban water supply planning and demand management. This approach compares water supply options using the Water Evaluation and Planning tool (WEAP) and a drought resilience matrix. Future implications of modeled climate change, extreme drought, and population increase effects on the natural and urban water system are explored in this study. The effectiveness of water supply portfolios is compared through the creation and use of a drought resilience matrix.Item The Effects of Coal Ash Storage Facilities on Aquatic Biota(2018) Edmonds, Shannon Michelle; Yonkos, Lance T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dry storage of coal combustion wastes (CCW) can negatively impact the surrounding environment. CCW leachates are characterized by low pH and high conductivity and are often enriched with metals and metalloids that threaten nearby ecosystems. In the present study, a quarterly series of whole effluent toxicity (WET) tests were completed on facility-treated discharge samples from three Maryland CCW disposal facilities. Priority metals and major ions were measured over time and concurrently with bioassays. Chronic toxicity was identified at all three locations at varying frequencies. The wastewaters were consistently high in total dissolved solids (TDS) with high conductivities, evidence that major ion toxicity could be contributing to the effects. Traditional Phase I Toxicity Identification Evaluation methods do not address these issues. Therefore, the present study evaluated the toxicity associated with major ion imbalances using mock effluents and a weight-of-evidence approach in order to identify the primary causative ions.