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 Green Facade Energetics(2010) Price, Jeffrey; Tilley, David R; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rising energy costs and a warming climate create the need for innovative, low-carbon technologies that help cool buildings. We constructed four small buildings and instrumented them to measure the cooling effect of a green façade on their south and west walls. The green façade significantly reduced the temperature of the building's ambient air, exterior surface, and interior air, and the heat flux through the vegetated wall. Using a mathematical model, we determined that the whole-building cooling load reduction (1.4 to 28.4%) depended on building construction, green façade placement, and especially whether the windows were covered. An emergy analysis of a south-facing green façade revealed that the total emergy consumed could be balanced by the electricity saved from reduced air conditioning if the cooling load was reduced by at least 14%. With thoughtful design and placement of a green façade it can sustainably and effectively help cool buildings.Item Kinetics of Tetrachloroethene-Respiring Dehalobacter and Dehalococcoides Strains and Their Effects on Competition for Growth Substrates(2010) Lai, Yenjung; Becker, Jennifer G; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The chlorinated solvents tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants. Reductive dechlorination of PCE and TCE at contaminated sites is commonly carried out by dehalorespiring bacteria that utilize these compounds as terminal electron acceptors, but often results in the accumulation of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), rather than non-toxic ethene. This project focused on evaluating how interactions among dehalorespiring populations that may utilize the same electron acceptors, electron donors and/or carbon source may affect the extent of PCE dechlorination in situ. These interactions may be particularly important if both Dehalococcoides ethenogenes (Dhc. ethenogenes) and Dehalobacter restrictus (Dhb. restrictus) are present because these bacteria utilize the same electron donor (H2) and both respire PCE and TCE. However, unlike Dhc. ethenogenes, Dhb. restrictus cannot dechlorinate PCE beyond cDCE. Therefore, the outcome of the population interactions may determine the extent of detoxification achieved. Monod kinetic parameter estimates that describe chlorinated ethene and electron donor utilization by Dhc. ethenogenes and Dhb. restrictus at non-inhibitory substrate concentrations were obtained in batch assays. Substrate inhibition effects on both populations were also evaluated. Highly chlorinated ethenes negatively impacted dechlorination of the lesser chlorinated ethenes in both populations. In Dhc. ethenogenes, cometabolic transformation of VC was also inhibited by the presence of other chlorinated ethenes. PCE and TCE dechlorination by Dhb. restrictus was strongly inhibited by VC. The microbial interactions between Dhc. ethenogenes and Dhb. restrictus was investigated using reactors and mathematical models under engineered bioremediation and natural attenuation conditions. Under engineered bioremediation conditions, Dhc. ethenogenes became the dominant population, and the modeling predictions suggested that the inhibition of Dhb. restrictus by VC was a key factor in determining this outcome. Dechlorination rates by Dhb. restrictus appeared to be affected very little by low acetate concentrations under natural attenuation conditions, giving it an advantage over Dhc. ethenogenes, which requires relatively high acetate concentrations. This study highlighted that substrate interactions among dehalorespiring bacteria can influence their performance and contaminant fate under common bioremediation scenarios. A better understanding of the factors affecting the outcomes of these microbial interactions was achieved, which should aid in the design of successful bioremediation strategies.Item Utilization of Gypsum as a Filter Material in Agricultural Drainage Ditches: Impacts of Land Application on Soil Fertililty Conditions(2010) Grubb, Karen Lyn; McGrath, Joshua M.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) including gypsum to remove P from ditch flow. One projected advantage would be the potential application of spent PSMs to agricultural fields to provide nutrients for crop production after the filter has lost its effectiveness. The study evaluated the feasibility of this strategy. Gypsum was saturated at two levels on mass basis of P, and applied to two soil types, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated at 25° C, and samples were collected at 0, 1, 7, 28, 63, 91, 119, and 183 days after saturation.Item INVESTIGATING CRUMB RUBBER AMENDMENTS FOR EXTENSIVE GREEN ROOF SUBSTRATES(2010) Solano Torres, Sonia Lorelly; Lea-Cox, John D; Ristvey, Andrew G; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Extensive green roof systems can mitigate urban stormwater by capturing rainfall and reducing runoff volume. Green roof substrates, often made from expanded shales, slates and clays are fundamental for roof hydraulic dynamics, and for providing optimal plant growth conditions. However, these substrates occasionally impose load limitations for retrofitting existing infrastructure. This research studied recycled-tire crumb rubber, as a light-weight material for amending green roof substrates. Zinc release from crumb rubber was quantified, and the interactions with commercial rooflite® substrate and the effect of high Zn concentrations on the growth and uptake by Sedum were studied. Zn was found to leach from crumb rubber in quantities that could negatively affect plant growth; however, Zn was adsorbed onto cation exchange sites of the mineral and/or organic portion of rooflite®, preventing negative growth effects in Sedum. Crumb rubber could be utilized as an amendment with substrates having high cation exchange capacities.Item Redoximorphic Features Induced by Organic Amendments and Simulated Wetland Hydrology(2010) Gray, Adam Lincoln; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)During wetland construction, it is common to add organic amendments to the soil, although little research has evaluated the effects of organic additions on the development of redoximorphic features. The objective of this study was to evaluate the effects of adding different types of organic materials, using different methods of incorporation, on the formation of redoximorphic features under hydric soil conditions. Five types of organic materials were incorporated into soil cores lacking redoximorphic features, using three incorporation methods. Cores were established as mesocosms in a controlled greenhouse environment or transplanted into a natural wetland. Mesocosms were periodically dissected and examined for newly formed redoximorphic features. The method of incorporating organic materials had a significant influence on the development of redoximorphic features, but the type of organic material had no significant effect. Organic materials should be concentrated into deeper zones during wetland construction to maximize development of redoximorphic features.Item HOUSEHOLD ENERGY USE, INDOOR AIR POLLUTION, AND HEALTH IMPACTS IN INIDA [i.e. India]: A WELFARE ANALYSIS(2009) Zhang, Yabei; Just, Richard; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation develops a unified analytical framework to understand the relationships among household energy use, indoor air pollution (IAP), and health impacts and enables policy-makers to analyze welfare effects of various interventions. This unified analytical framework includes four interlinked modules. Module 1 studies the determinants of IAP and constructs an IAP index to predict typical IAP exposure. Module 2 analyzes the impacts of IAP exposure on health, including both self-reported respiratory symptoms and physician-measured spirometry indicators. Module 3 uses a novel approach to model household behavior regarding energy technology choices based on utility maximizing behavior. Households are assumed to choose a cooking energy technology based on its attributes: cooking cost, convenience, and cleanliness. Household valuation of these attributes depends on household characteristics. Then based on the household utility function estimated from Module 3, Module 4 evaluates welfare change from various policy interventions. Empirical estimation relies primarily on two surveys recently conducted in India: a social science and environmental health survey entitled Health, Environment, and Economic Development and a multi-topic national representative sample survey called the India Human Development Survey. The two surveys were fielded between late 2004 and early 2005 and contain uniquely rich information on household energy use, indoor air pollution levels, and health indicators. This dissertation provides quantitative evidence that IAP has significant health impacts comparable to smoking. Based on analysis of IAP impacts on spirometry indicators, the evidence suggests that IAP has major impacts on restrictive lung disease rather than obstructive lung disease. These results explain why certain diseases are more highly associated with IAP exposure. Considering that traditional biomass will likely continue to be the most popular cooking fuel in rural areas of India in the near future, and that households can achieve considerable welfare gains from improvement in stoves and kitchen ventilation, the analysis suggests that the Indian government should consider reviving the improved stove program with a new advanced stove strategy coupled with conducting advocacy campaigns on how to improve kitchen ventilation. The analysis suggests small overall welfare effects of the pending phasing out of LPG subsidies.Item Evaluation of the effects of wetland restoration design on hydraulic residence time and nutrient retention(2009) Strano, Stephen; Felton, Gary K; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hydraulic residence time (HRT) is a critical factor that can be integrated into wetland restoration designs to promote nutrient retention, but HRT in the context of wetlands with storm-driven hydrology is not well understood. A model for nutrient retention optimization based on HRT was evaluated using three indicators of HRT and nutrient stocks in above-ground plant biomass. Results indicated that a commonly used indicator of HRT, the ratio of wetland to watershed area, may be insufficient, while nominal HRT provided an overestimate for wetlands receiving storm runoff. While there was little relationship between total nitrogen and HRT, results suggested that HRT may explain some variation in total phosphorus. Results also indicated that the studied wetland restorations were not designed to provide sufficient HRT to promote the retention of dissolved nutrients, and that staged outlets could be used to provide significant HRT's for a range of storm events.Item HYDROMORPHOLOGY OF ANOMALOUS BRIGHT LOAMY SOILS ON THE MID-ATLANTIC COASTAL PLAIN(2009) Zurheide, Philip Klaus; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Some loamy textured soils along the Mid-Atlantic coastal plain undergo extended periods of saturation or ponding, yet lack the hydromorphology that identifies them as hydric by any of the currently approved Field Indicators of Hydric Soils (FI). Termed Anomalous Bright Loamy Soils (ABLS), these were identified at four research sites on the Delmarva Peninsula. The hydrologic and biogeochemical status of these soils was monitored for three years along a hydrosequence at each site. A series of field and lab experiments were run to investigate the possible causes for the ABLS-phenomenon. The most likely cause is a combination of low hydrologic gradient coupled with the length of time since saturation. Using observed morphology, a newly developed Field Indicator successfully discriminated between five hydric soils that lacked an approved indicator and those that were not hydric. This indicator has now been approved as an official FI of Hydric Soils (F20).Item Pedogenesis in Rain Gardens: The Role of Earthworms and Other Organisms in Long-Term Soil Development(2009) Ayers, Emily Mitchell; Kangas, Patrick; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As bioretention comes into widespread use, it has become increasingly important to understand the development of bioretention soils over time. The objective of this research is to investigate the development of bioretention soils and the importance of ecological processes in the performance of rain gardens. The research includes descriptive studies of pre-existing rain garden soil profiles, laboratory experiments quantifying the effect of earthworms on infiltration rates, and a simulation model describing the influence of earthworms and soil organic matter on infiltration. Surveys of several different rain gardens of various ages provide the first detailed descriptions of rain garden soil profiles. The study revealed a great deal of biological activity in rain gardens, and evidence of pedogenesis even in very young sites. The uppermost soil layers were found to be enriched with organic matter, plant roots, and soil organisms. The field sites surveyed showed no signs of clogging due to the trapping of suspended solids carried in stormwater runoff. Some evidence was found of higher than expected infiltration rates at the field sites, which may be attributable to the effects of bioturbation by living organisms. The ability of earthworms to mitigate the effects of trapped suspended solids on bioretention soils was assessed in the laboratory. Results show that earthworms are capable of maintaining the infiltration rate of bioretention soils, but that their effects have a high degree of variability. This variability is attributed to soil aggregate instability caused by the oversimplification of the ecosystem. Other organisms play a significant role in stabilizing earthworm burrows and casts, and may be essential ingredients in a self-maintaining bioretention ecosystem. A simulation model of the action of earthworms on soil infiltration rates was developed in order to illustrate the physical processes taking place as a result of earthworm activity. The model was calibrated using data from the field study and microcosm experiment. This research is intended to provide a first glimpse into the biological processes at work in rain garden soils. The research shows that soil organisms are present in rain gardens, and suggests that their impact on bioretention performance may be significant.Item Use of Macroinvertebrate Predictive Models to Evaluate Stream Restoration Effect(2008-09-03) Tsang, Yin-Phan; Felton, Gary K; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Multivariate analysis was used to build macroinvertebrate predictive models for stream assessment in Britain, Australia, and the west coast of the United States. The philosophy behind these predictive models was similar, but variations exist and have been adapted for different regions. The macroinvertebrate predictive model in Maryland has been improved using Region-style models, including the Assessment by Nearest Neighbour Analysis (ANNA), the Burn's Region of Influence (BROI), and the New Datum Region of Influence (NROI) predictive schemes. For better prediction precision, different parameter selection methods (stepwise AIC, exhaustive AIC, and exhaustive BIC) and rational multiple regression function checking have been used to prevent overfitting. Root mean squared error (RMSE) was used to select the final best model. The calibration results from the Region-Style models are better than those from previously built River InVertebrate Prediction And Classification System (RIVPACS)-style model. The different parameter selection criteria along with rational regression function checking discourage overfitting and improve the prediction results. Region-style methods can be alternative methods for building predictive model. GISHydro2000 is a GIS-based program for performing hydrologic analysis in Maryland. This tool was used to determine numerous hydrologic characteristics as potential predictors to be used in the macroinvertebrate predictive model. The best performing ANNA, BROI, and NROI predictive models can be automated in the GISHydro2000 environment. Theses multivariate analyses (i.e., Observed/Expected (O/E) scores), as well as multimetric analysis (i.e., Benthic Index of Biotic Integrity (IBI) metrics), were applied to evaluate the stream restoration sites in Montgomery County, Maryland. The evaluation results show most stream habitat conditions were still degraded after stream restoration projects. The environmental stressors at the stream site were not immediately alleviated by the restoration design, or the stressors overshadowed the restoration efforts. At many sites, the stream condition starts to recover at the 3rd- or 4th- year post-restoration. More time may be needed for monitoring the recovery of stream ecosystems. The benthic IBI metrics response to not only environmental stressor, but also other natural variances. The results suggested that O/E scores from multivariate analysis provides valuable supplemental information for evaluating stream health.