Environmental Science & Technology Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2748

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Advanced imaging and data mining technologies for medical and food safety applications
(2009) Jiang, Lu; Tao, Yang; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
As one of the most fast-developing research areas, biological imaging and image analysis receive more and more attentions, and have been already widely applied in many scientific fields including medical diagnosis and food safety inspection. To further investigate such a very interesting area, this research is mainly focused on advanced imaging and pattern recognition technologies in both medical and food safety applications, which include 1) noise reduction of ultra-low-dose multi-slice helical CT imaging for early lung cancer screening, and 2) automated discrimination between walnut shell and meat under hyperspectral florescence imaging. In the medical imaging and diagnosis area, because X-ray computed tomography (CT) has been applied to screen large populations for early lung cancer detection during the last decade, more and more attentions have been paid to studying low-dose, even ultra-low-dose X-ray CTs. However, reducing CT radiation exposure inevitably increases the noise level in the sinogram, thereby degrading the quality of reconstructed CT images. Thus, how to reduce the noise levels in the low-dose CT images becomes a meaningful topic. In this research, a nonparametric smoothing method with block based thin plate smoothing splines and the roughness penalty was introduced to restore the ultra-low-dose helical CT raw data, which was acquired under 120 kVp / 10 mAs protocol. The objective thorax image quality evaluation was first conducted to assess the image quality and noise level of proposed method. A web-based subjective evaluation system was also built for the total of 23 radiologists to compare proposed approach with traditional sinogram restoration method. Both objective and subjective evaluation studies showed the effectiveness of proposed thin-plate based nonparametric regression method in sinogram restoration of multi-slice helical ultra-low-dose CT. In food quality inspection area, automated discrimination between walnut shell and meat has become an imperative task in the walnut postharvest processing industry in the U.S. This research developed two hyperspectral fluorescence imaging based approaches, which were capable of differentiating walnut small shell fragments from meat. Firstly, a principal component analysis (PCA) and Gaussian mixture model (PCA-GMM)-based Bayesian classification method was introduced. PCA was used to extract features, and then the optimal number of components in PCA was selected by a cross-validation technique. The PCA-GMM-based Bayesian classifier was further applied to differentiate the walnut shell and meat according to the class-conditional probability and the prior estimated by the Gaussian mixture model. The experimental results showed the effectiveness of this PCA-GMM approach, and an overall 98.2% recognition rate was achieved. Secondly, Gaussian-kernel based Support Vector Machine (SVM) was presented for the walnut shell and meat discrimination in the hyperspectral florescence imagery. SVM was applied to seek an optimal low to high dimensional mapping such that the nonlinear separable input data in the original input data space became separable on the mapped high dimensional space, and hence fulfilled the classification between walnut shell and meat. An overall recognition rate of 98.7% was achieved by this method. Although the hyperspectral fluorescence imaging is capable of differentiating between walnut shell and meat, one persistent problem is how to deal with huge amount of data acquired by the hyperspectral imaging system, and hence improve the efficiency of application system. To solve this problem, an Independent Component Analysis with k-Nearest Neighbor Classifier (ICA-kNN) approach was presented in this research to reduce the data redundancy while not sacrifice the classification performance too much. An overall 90.6% detection rate was achieved given 10 optimal wavelengths, which constituted only 13% of the total acquired hyperspectral image data. In order to further evaluate the proposed method, the classification results of the ICA-kNN approach were also compared to the kNN classifier method alone. The experimental results showed that the ICA-kNN method with fewer wavelengths had the same performance as the kNN classifier alone using information from all 79 wavelengths. This demonstrated the effectiveness of the proposed ICA-kNN method for the hyperspectral band selection in the walnut shell and meat classification.
Advancing Ecosystem Based Fisheries Management: Biological Reference Points for Nutritional Status of Striped Bass (Morone saxatilis)
(2014) Haus, William; Harrell, Reginal M; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Nutritional condition is a valuable metric in ecosystem-based fisheries management. However, the need for lethal sampling for the most accurate indicators ethically and logistically limits sample sizes. Percent moisture has been recommended for management of striped bass Morone saxatilis and a management threshold has been suggested. Past researchers have used bioelectrical impedance analysis (BIA) to non-lethally estimate percent dry weight, the inverse of percent moisture. We sought to develop species-specific BIA models for striped bass in a controlled, laboratory setting and later validate those models with independent, field-collected data. BIA models were developed for five size classes and sampled across three temperatures. Results in the lab suggest BIA is an accurate and robust method for estimating percent dry weight in striped bass. However, when implemented in field surveys results are less conclusive. Possible differences between wild and hatchery-reared striped bass that effect BIA need further exploration. Additionally, the effects of salinity and stress response on BIA warrant further work.
Alternative Simulation of Soil Phosphorus for Agricultural Land Uses in the Chesapeake Bay Watershed Model
(2014) Mulkey, Alisha Spears; Coale, Frank J; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Current restoration efforts for the Chesapeake Bay watershed mandate reducing nutrient and sediment loads to receiving waters. The Chesapeake Bay Watershed Model (WSM) estimates loading; however, some WSM routines have not been updated to reflect recent research. This study's objective was to improve the simulation of soil phosphorus dynamics by using an independent modeling tool (APLE) as an alternative to the current WSM approach. Identical assumptions of acreage, soil properties, nutrient management, and transport factors from the WSM were used as inputs to APLE. Outcomes represent revised estimates of phosphorus edge-of-field losses and estimates of change in soil labile phosphorus concentration. The modification resulted in a greater mean phosphorus loss estimate compared to the WSM, and a relationship between nutrient application, tillage, and soil phosphorus concentrations. Outcomes support APLE as an appropriate alternative model for simulating soil phosphorus dynamics, and for informing mitigation of soil phosphorus losses through best management practices.
Anthropogenic disturbance alters plant and microbial communities in tidal freshwater wetlands in the Chesapeake Bay, USA
(2019) Gonzalez Mateu, Martina; Yarwood, Stephanie A; Baldwin, Andrew H; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Tidal freshwater wetlands are often found near urban centers, and as a result of human development they are subject to multiple environmental stressors. Increases in nutrient runoff, sedimentation, and hydrologic alterations have had significant impacts on these systems and on the ecosystem services they provide. One of the consequences of these stressors is the expansion of invasive species that can affect native biodiversity and the many biogeochemical processes that are key to wetland ecosystem function. This research looked at how human activities affect microbial communities in tidal freshwater wetlands, and explored various aspects of an invasive plant’s ecology in the Chesapeake Bay. In our first study, we found that microbial community composition differed along a rural to urban gradient and identified microbial taxa that were indicators of either habitat. Rural sites tended to have more methanogens and these were also indicators in these system, whereas in urban systems nitrifying bacteria were the main indicator taxa. This study suggested that urban wetlands have different microbial communities and likely different functions than those in rural areas, particularly concerning nitrogen and contaminant removal. Our second study looked at management of an invasive lineage of Phragmites australis which is commonly found in wetlands impacted by nitrogen enrichment. We evaluated the effects of different C:N ratios on the competitive ability of this lineage and a native North American lineage. Even though carbon addition did not improve the native’s competitive ability, we identified facilitative interactions when both lineages were growing together. This suggests that native and invasive Phragmites might coexist if there are no additional disturbances to the system. Our last study focused on plant-fungal interactions, and found that both Phragmites lineages benefitted from inoculation with fungal endophytes under salt stress. These results suggest that studies of plant-fungal interactions can yield insights into mechanisms of invasion, and could be further investigated in native wetland plants susceptible to increased salt stress following sea-level rise. Our results provide insights into plant and microbial ecology in the Chesapeake Bay’s tidal freshwater wetlands, and improve our understanding of the invasion process and management strategies of Phragmites australis.
ANTHROPOGENIC INFLUENCES ON BOTTOM-UP AND TOP-DOWN REGULATION OF ANIMAL DISTRIBUTIONS, POPULATIONS, AND BEHAVIORS IN URBAN ENVIRONMENTS
(2024) Herrera, Daniel Joseph; Gallo, Travis; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Animal populations are simultaneously governed by both bottom-up (e.g., habitat availability) and top-down (e.g., predation) regulation. While ecologists historically sought to differentiate the roles of bottom-up and top-down regulation on ecosystems, the two are not so easily defined in urban ecosystems due to the immense influence humans have on ecological processes in cities. In Chapter One, I present this argument from a philosophical perspective and comment on how this philosophy has shaped my worldview. In Chapter Two, I examine the legacy of historical park planning on urban bird assemblages using archived municipal maps and historical bird data. My analysis found a positive correlation between percent park area and both species richness and functional richness of birds. Additionally, I found the effect size of park area was larger than the effect of certain life history traits thought to facilitate urban exploitation. These results indicate that landscape features and life history traits are equally responsible for the success of synurbic species. Chapter Three explores the effect of urbanization on animal behavior by analyzing anti-predator behavior of white-tailed deer (Odocoileus virginianus) in relation to ambient light, noise, and human activity. Despite negligible predation risk in my study area, deer expressed higher vigilance behavior in dark and noisy conditions, and increased their foraging group size during noisy conditions. These results suggest that anti-predator behaviors are a response to the perception of predation risk rather than a response to the actual presence of predators. Although predation of deer is rare in urban ecosystems, predation of smaller wildlife species by mesopredators, such as non-native domestic cats (Felis catus) is common. Chapter Four examines the potential for predation and zoonotic disease transmission between cats and eight native mammals by estimating the spatial and temporal overlap between species. I found that cat distribution was largely driven by anthropogenic features, whereas native wildlife was generally deterred by anthropogenic features and instead occupied forested areas. I also found that cats, as a species, were active on the landscape during the full 24-hour cycle. As a result, while spatial overlap between cats and wildlife varied across the study area, temporal overlap was possible anywhere cats and wildlife co-occurred. Chapter Five expands on Chapter Four and investigates predation directly by using observations of cats carrying prey documented by motion-activated cameras. I found that predation by cats was higher in areas where supplemental cat food was prevalent, but declined near forested areas. Additionally, my results indicate that cats within 250 meters of a forest edge predominantly preyed on native wildlife, whereas cats generally preyed on non-native rats (Rattus norvegicus) when greater than 250 meters from a forest edge. Each chapter provides applied recommendations to the management and conservation of urban wildlife, but together, my work demonstrates the entanglement of bottom-up, top-down, and anthropogenic forces in urban ecosystems. In light of these findings, I advocate for a more nuanced understanding of ecosystem regulation through a socio-ecological lens.
APPLICATION OF RECLAIMED WASTEWATER FOR AGRICULTURAL IRRIGATION: DEVELOPING A DECISION SUPPORT TOOL USING SPATIAL MULTI-CRITERIA DECISION ANALYSIS
(2020) Paul, Manashi; Negahban-Azar, Masoud; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Intensified climate variability, depleting groundwater, and escalating water demand create severe stress on high-quality freshwater sources used for agricultural irrigation. These challenges necessitate the exploration of alternative water sources such as reclaimed water to reduce the pressure on freshwater sources. To do so, it is key to investigate the spatial pattern of areas that are more suitable for water reuse to determine the potential of reclaimed wastewater use for irrigation. This study provides a systematic decision-analysis framework for the decision-makers using an integrated process-based hydrologic model for sustainable agricultural water management. The outcomes of this study provide evidence of the feasibility of reclaimed wastewater use in the agricultural sector. The two objectives of this study were to: 1) identify the locations that are most suitable for the reclaimed wastewater use in agriculture (hotspots); and 2) develop the watershed-scale models to assess the agricultural water budget and crop production using different water conservation scenarios including reclaimed wastewater use. To achieve the first objective, a decision-making framework was developed by using the Geographic Information System and Multi-Criteria Decision Analysis (GIS-MCDA). This framework was then tested in the Southwest (California), and the Mid-Atlantic (Maryland) regions. Based on WWTPs’ proximity, sufficient water availability, and appropriate treatment process of the treated wastewater, the “Most Suitable” and “Moderately Suitable” agricultural areas were found to be approximately 145.5 km2, and 276 km2 for California and, 26.4 km2 and 798.8 km2 for Maryland, respectively. These results were then used to develop the hydrologic models to examine water conservation and water reuse scenarios under real-world conditions, using the Soil and Water Assessment Tool (SWAT). In California, the combination of auto irrigation (AI) and regulated deficit irrigation (RDI) resulted in higher WP for both almond and grape (> 0.50 kg/m3). Results also suggested that the wastewater reuse in almond and grape irrigation could reduce groundwater consumption more than 74% and 90% under RDI and AI scenarios, respectively. For Maryland, model simulations suggested that the green water productivity (only rainfall) can be improved up to 0.713 kg/m3 for corn and 0.37 kg/m3 for soybean under the reclaimed wastewater use scenario.
Assessing the uncertainty of emergy analyses with Monte Carlo simulations
(2012) Hudson, Amy; Tilley, David R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Crop production systems were used to show the presence and propagation of uncertainty in emergy analyses and the effect of source variance on the variance of the yield unit emergy value (UEV). Data on energy/masses and UEVs for each source and yield were collected from the emergy literature and considered as inputs for the Monte Carlo simulation. The inputs were assumed to follow normal, lognormal, or uniform probability distributions. Using these inputs and a tabular method, two models ran Monte Carlo simulations to generate yield UEVs. Supplemental excel files elucidate the Monte Carlo simulations' calculations. The nitrogen fertilizer UEV and net topsoil loss energy were the inputs with the largest impact on the variance of the yield's UEV. These two sources also make the largest emergy contributions to the yield and should be the focus of a manager intent on reducing total system uncertainty. The selection of a statistical distribution had an impact on the yield UEV and thus these analyses may need to remain system- or even source- specific.
Assessing Wetland Restoration on the Delmarva Peninsula using Vegetation Characteristics
(2015) McFarland, Eliza Katherine; Baldwin, Andrew H; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
With wetland restoration, post-restoration monitoring is essential for determining developmental trajectories, particularly when comparing to natural reference systems. As part of the Mid-Atlantic Conservation Effects Assessment Project, 15 depressional wetlands on the Delmarva Peninsula of Maryland and Delaware were surveyed for above-ground vegetation and seed bank community composition, annual biomass production, and vegetation carbon content (10 restorations from prior-converted cropland (aged 5-31 years), and 5 natural forested depressions). Within each wetland, hydrologic zones (emergent, transition, upland) were also denoted and sampled. Restored wetlands showed more seed bank community similarity to natural wetlands than above-ground vegetation communities. Restorations also produced more annual herbaceous biomass than natural systems, and lower annual leaf litter biomass. After this period of post-restoration development, restored wetlands do not perform vegetation-related functions identical to their natural counterparts; however, these restorations are performing important vegetation-based functions that require yet more time to truly develop.
Assessment of nitrogen status and vegetation composition in tidal freshwater marshes using partial least squares regression models of hyperspectral canopy reflectance
(2006-04-28) Jenkins, Emily Poynter; Tilley, David R; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Hyperspectral canopy reflectance was used to predict sub-surface water nutrients, vegetation composition, and canopy nutrients, which could lead to more useful means for assessing the status of wetlands. Thirty field quadrats at two tidal freshwater marsh sites on the Nanticoke River (Maryland) were treated with five nitrogen levels. During the 2004-05 growing seasons, hyperspectral canopy reflectance was measured using a spectroradiometer with 1nm resolution across the visible and near - infrared spectrum (350-1075 nm), water samples were collected using lysimeters, species cover was quantified, and biomass was collected and analyzed for canopy nutrients. ANOVA was used to determine whether nitrogen affected reflectance, species composition, canopy N and P, and partial least squares regression was used to develop reflectance models predictive of these ecosystem properties. Results indicated that hyperspectral radiometry could be used as a remote sensing tool for quantifying sub-surface water nitrogen, vegetation composition, and canopy nutrients in tidal freshwater marshes.
AUGMENTING SEQUENCING TECHNOLOGY FOR BETTER INFERENCE IN SOIL MICROBIOME ANALYSIS
(2023) Epp Schmidt, Dietrich; Yarwood, Stephanie A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The advent of DNA sequencing revolutionized the field of microbiome research. Many organisms, by virtue of their codependence and/or growth rate, are either impossible or extremely challenging to get into pure culture. Sequencing allows important taxonomic and phylogenetic information to be obtained independent of culturing. Development of the sequencing technology itself has allowed for high throughput workflow that has allowed low cost and extensive sampling of microbiomes across environments. The co-development of reference datasets for taxonomy and functional assignments, along with open-source bioinformatics pipelines has further empowered scientists to explore microbiomes in many environments. However, there are limitations to sequence data that have constrained the ecological inferences in microbiome research. One such limitation, the compositional nature of sequence data, has impeded our ability to make accurate inferences about the environmental drivers of taxon abundance and covariance across conditions. In this dissertation I explore the use of quantitative PCR in combination with sequencing techniques to generate “Quantitative Sequencing” data (QSeq) that mitigates the limitations of compositionality on inferences relating to taxon abundance and covariance across environmental gradients. In chapter 1, I reviewed key characteristics of the soil environment and sequencing as a mechanism for sampling. In chapter 2, I leveraged modeling, synthesis, and literature review methods to establish the questions and data characteristics that demand QSeq methodology. I show that even small amounts of variation in total abundance make determining the effects of environment (biotic and abiotic factors) on any given taxon unreliable without QSeq. In Chapter 3, I extend the logic of quantitative sequencing to improve metagenome prediction from PICRUSt2. Using data synthesis methods, accounting for 16S gene abundance consistently improved the accuracy of predicted functional genes. This was confirmed by high correlations between predicted and measured gene abundance (QPCR). There was however a large variation in prediction accuracy, likely due in part to database biases and in part to decoupling of bacterial function from taxonomy. In Chapter 4, I applied QSeq in the context of an experimental, long-term farming system that has large gradients in total abundance with depth, and I used QSeq to identify taxa that changed in abundance due to different farming system management and soil depth. Finally in Chapter 5, I used QSeq to identify putative N-fixing taxa that responded to glyphosate in four experimental farming systems. I show that the abundance of these taxa were decoupled from other effects of glyphosate on N-fixation in soybean across farming systems.
Back to Earth: Molecular Approaches to Microbial Ecology Must Consider Soil Morphology and Physicochemical Properties
(2015) Dlott, Glade; Yarwood, Stephanie A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This project studied the influence of different long-term agricultural management regimes on soil microbial communities, and compared survival strategies of individual prokaryotic OTUs in diverse soils subjected to long-term incubation. Together these would show whether alterations to microbial communities affect rates of soil carbon cycling. Agricultural soils were sampled at arbitrary depths above and below the plow layer, and relative abundances of microbes were measured using high-throughput sequencing. `Activity' (rRNA:rDNA) ratios were calculated for individual OTUs identified by high-throughput sequencing of tropical rainforest and temperate cornfield soils after incubation for one year with differing water and carbon availabilities. It was found that depth controls microbial communities to a greater degree than agricultural management, and that the characterization of microbial trophic strategies might be complicated by the often-ignored DNA preservation potential of soil. The study highlights the need for holistic approaches to testing hypotheses in modern microbial ecology.
BALD EAGLE (HALIAEETUS LEUCOCEPHALUS) POPULATION PRODUCTIVITY AND DENSITY DEPENDENT EFFECTS IN MICHGAN, 1961-2010
(2013) Simon, Kendall Lyn; Bowerman, William W; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The bald eagle (Haliaeetus leucocephalus) population in Michigan has undergone a significant recovery following the ban of the pesticide dichlorodiphenyltrichloroethane (DDT), and its subsequent derivatives, mainly dichlorodiphenyl-dichloroethylene (p,p'-DDE). This recovery however, has not been uniform throughout the state. Michigan is a heterogeneous habitat, causing the best-fit, experienced breeding pairs to settle in high quality breeding areas first. This high quality habitat mainly occurs in the inland regions of Michigan. These areas experienced the greatest productivity until the 1990's, quickly recovering from the detrimental effects of DDT. Great Lakes breeding areas, particularly Lake Michigan and Lake Huron, are now more productive than inland breeding areas. These Great Lakes breeding pairs however, are the least efficient breeders with greater amounts of changeover between nesting pairs within one breeding area in comparison to inland pairs. A constant turnover of breeding pairs may overshadow any underlying effects causing decreased reproductive fitness in Great Lakes adults.
BALD EAGLES (HALIAEETUS LEUCOCEPHALUS) AS INDICATORS OF GREAT LAKES ECOSYSTEM HEALTH
(2016) Simon, Kendall Lyn; Bowerman, William W; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Environmental indicators have been proposed as a means to assess ecological integrity, monitoring both chemical and biological stressors. In this study, we used nestling bald eagles as indicators to quantify direct or indirect tertiary-level contaminant exposure. The spatial and temporal trends of polychlorinated biphenyl (PCB) congeners were evaluated in nestling plasma from 1999–2014. Two hexa-chlorinated congeners, PCB-138 and 153, were detected with the highest frequency and greatest concentrations throughout Michigan. Less-chlorinated congeners such as PCB-52 and 66 however, comprised a greater percentage of total PCB concentrations in nestlings proximate to urbanized areas, such as along the shorelines of Lake Erie. Toxic equivalents were greatest in the samples collected from nestlings located on Lake Erie, followed by the other Great Lakes spatial regions. Nestling plasma samples were also used to measure concentrations of the most heavily-used group of flame retardants, brominated diphenyl ethers (BDEs), and three groups of alternative flame retardants, non-BDE Brominated Flame Retardants (NBFRS), Dechloranes, and organophosphate esters (OPs). BDE-47, 99 and 100 contributed the greatest to total BDE concentrations. Concentrations of structurally similar NBFRs found in this study and recent atmospheric studies indicate that they are largely used as replacements to previously used BDE mixtures. A variety of Dechloranes, or derivatives of Mirex and Dechlorane Plus, were measured. Although, measured at lesser concentrations, environmental behavior of these compounds may be similar to mirex and warrant future research in aquatic species. Concentrations of OPs in nestling plasma were two to three orders of magnitude greater than all other groups of flame retardants. In addition to chemical indicators, bald eagles have also been proposed as indicators to identify ecological stressors using population measures that are tied to the fitness of individuals and populations. Using mortality as a population vitality rate, vehicle collisions were found to be the main source of mortality with a greater incidence for females during white-tailed deer (Odocoileus virginianus) hunting months and spring snow-melt. Lead poisoning was the second greatest source of mortality, with sources likely due to unretrieved hunter-killed, white-tailed deer carcasses, and possibly exacerbated by density-dependent effects due to the growing population in Michigan.
Biomonitoring organochlorine compounds using bald eagles (Haliaeetus leucocephalus) in Voyageur's National Park 2011-2017 and developing new biomonitoring techniques
(2018) Eberius, Rachel Ann; Bowerman, William W; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Wildlife are used to monitor the presence and persistence of legacy organochlorine contaminants in the environment. In this study, bald eagles (Haliaeetus leucocephalus) were utilized as an indicator of exposure to organochlorine compounds at Voyageur’s National Park, Minnesota from 2011-2017. This demonstrated decreasing concentration trends and a lack of recent inputs of organochlorine compounds. However, the use of organochlorine compounds continues in other parts of the world. Therefore, a technique for using solid phase extraction to quantify organochlorine analytes in avian plasma was developed in order to facilitate international biomonitoring of these compounds. Using this method, organochlorine compounds are extracted from plasma and stored within extraction cartridges during transport from collection site to analysis site. This has important implications for international wildlife biomonitoring. If organochlorine analytes are separated from their matrix at the site of collection, sensitive or hazardous biological materials do not need to be transported or stored.
Biosolids and Compost For Urban Soil Restoration and Forestry
(2022) Keener, Emily Cathryn; Pavao-Zuckerman, Mitchell A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Elements of urban soil quality such as compaction and low organic matter are underexamined, important challenges to urban afforestation. In this Beltsville, Maryland field experiment, I examined biosolids and compost as amendments to improve soil quality and planted tree survival in a degraded urban proxy soil and identified correlations between soil properties and tree survival. Organic amendments increased organic matter content, decreased bulk density, and had no effect on tree survivorship compared to controls. Effects on soil were more profound and lasting with compost than with biosolids. Soil organic matter and bulk density were correlated with tree survival early in the study and microbial respiration was correlated with tree survival throughout the study. High tree mortality was driven by transplant shock, limiting insights from tree response data. This study highlights the importance of soil quality and good planting practices in future research.
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.
Carbon Storage and Potential Carbon Sequestration in Depressional Wetlands of the Mid-Atlantic Region
(2011) Fenstermacher, Daniel E.; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
With recent concern over climate change, methods for decreasing atmospheric levels of greenhouse gasses such as CO₂ have been of particular interest, including carbon sequestration in soils that have depreciated levels of carbon from cultivated agricultural crop production. The Delmarva Peninsula contains many Delmarva Bay landforms, which commonly contain wetlands. Five pairs of Delmarva Bays were selected to examine change in carbon stocks following conversion to agriculture and to assess the potential for carbon sequestration if these soils were to be restored hydrologically and vegetatively. A loss of approximately 50 % of the stored soil carbon was observed following the conversion to agriculture. If these agricultural soils were to be restored, the wetland soils within the Delmarva Bay basin are predicted to sequester a total of approximately 11 kg C m-2 and the upland soils of the rim would be expected to sequester a total of approximately 4 kg C m-2.
Characterization of Plant Root Cell Wall Structural Changes During Decomposition
(2015) White, Kathryn Ella; Coale, Frank J; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Plant roots are important contributors of organic carbon compounds for soil organic matter (SOM) formation, particularly hemicellulose, cellulose and lignin, but little is known about the composition of many species. Knowledge of compositional changes as plant roots decompose is also limited. This information is essential to understand the role of root-derived macromolecules in SOM dynamics and carbon sequestration. The paucity of available data necessitates analytical techniques to assess root composition and changes during decomposition. The objectives of this research were to evaluate diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for assessment of root cell wall composition and to quantify and characterize changes in the cell wall composition of important crop and forage species during decomposition in 30 and 270 day incubations. Results indicate that the roots of the same species are similar despite differences in climate, soil and fertilization, while important differences were noted between roots of different species. Spectral analysis was consistent with chemical fiber analysis composition data and revealed features that may be indicative of root suberin content. Between Day 0 and Day 30 significant (P<0.05) changes in alfalfa root hemicellulose, cellulose and lignin were observed as roots became enriched with lignin relative to hemicellulose and cellulose. No changes were observed in the other studied roots over this interval. In the 270 day incubation large species dependent variations were observed in the extent of root tissue decomposition. In contrast to the short term results, lignin, cellulose and hemicellulose in the roots of all studied species degraded proportionally over time. Analysis by DRIFTS supported the fiber analysis results and revealed important changes as roots decompose. Spectra illustrated changes in hemicellulose structure and potential suberin preservation in decomposing roots. These results help to increase understanding and prediction of soil organic matter dynamics which will help to predict possible impact of management changes or soil disturbance on soil health and productivity as well as long term organic carbon stabilization and the potential for C sequestration. Variability in root composition and degradation suggest that characterization of a range of individual species is necessary to predict the soil carbon contribution from roots.
CHROMIUM OXIDATION AND REDUCTION BY HYDROGEN PEROXIDE IN DIVERSE SOILS AND SIMPLE AQUEOUS SYSTEMS
(1999) Rock, Melanie Louise; Helz, George R.; James, Bruce R.; Chemistry; Environmental Science & Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Hydrogen peroxide is being tested for in situ remediation of buried contaminants - either as a direct chemical oxidant in Fenton-type reactions or as a source of oxidizing equivalents in bioremediation. How it affects a common co-contaminant, Cr, is explored here in four chemically diverse high-Cr soils. Soils contaminated with high levels of soluble Cr(VI) from ore processing and soils containing high levels of recently reduced Cr(III) from electroplating waste showed marked increases in chromate after single applications of J-25 mM peroxide. Cr(VI) in the leachates exceeded the drinking water standard (2μM) by 1-3 orders of magnitude. Soluble Cr(III), in the form of dissolved organic complexes, contributed to the likelihood of Cr(III) oxidation. Anaerobic soil conditions at a tannery site prevented oxidation of Cr(III). Naturally occurring Cr in serpentine soil also resisted oxidation. Ambient soluble Cr(VI) in a contaminated aquifer disappeared from peroxide leachates below pH 5, then reappeared as peroxide levels declined. In solutions prepared under environmentally relevant conditions, aged 280 μM Cr(III) treated with 100 μM H2O2 showed increases in Cr(VI) over weeks with maximum oxidation rates achieved in solutions prepared with 2:1 and 4:1 OH^-:Cr. Although Cr(III) speciation differs in fresh and aged aqueous systems, a similar mechanism involving the pre-equilibrium step: Cr(OH)/ + OH- .,. Cr(OH)/ may account for Cr(III) oxidation in both systems. Under alkaline conditions, H2O2 enhanced the oxidative dissolution of Crn(OH)3n^0. The formation of peroxochromium compounds in the presence of H2O2 and Cr(VI) may account for the disappearance and reappearance of Cr(VI) in H2O2 treated soils; as does the possible formation and subsequent reoxidation of Crm\(OH)3n-2^2+ oligomers. Mobilization of hazardous Cr(VI) must be considered in plans to use H2O2 for remediation of chemically complex wastes. Once Cr(III) is oxidized to Cr(VI) by H2O2 it may persist long after applied H2O2 treatments have disappeared. Further, hexavalent Cr will behave as a catalyst toward H20 2 in soils, enhancing its oxidative capacity while helping to dissipate high levels of applied H2O2.
CHROMIUM OXIDATION-REDUCTION CHEMISTRY CONTROLLED BY IRON AND MANGANESE (HYDR)OXIDE SURFACES AND SOILS: COLUMN LEACHING AND SPECTROSCOPIC STUDIES
(2014) Miller, Christina Langlois; James, Bruce R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Soil interfaces, including those defined by horizons and iron (Fe(III)) and manganese (Mn(III,IV)) (hydr)oxide mineral surfaces, are a largely unstudied area in soils research, especially in terms of their oxidation-reduction properties. This study attempted to address two questions related to this research deficiency. The first: how chromium (Cr) redox changes throughout mineralogically different soil horizons, and the second: how Cr redox structurally alters Fe(III) and Mn(III,IV) (hydr)oxides in synthetic, soil, and microbial systems. Both parts of the study used column leaching experiments along with Cr speciation techniques to study simulated soil horizon interfaces and Fe/Cr and Mn/Cr redox systems. X-ray absorption spectroscopic techniques were also utilized to analyze the mineral structure of Fe(III) and Mn(III,IV) (hydr)oxides. The results of the study indicate that there are significant interfacial properties affecting Cr(VI) reduction and that Cr(III) oxidation does change the mineral structures of synthetic, soil, and fungal Mn(III,IV)(hydr)oxides to varying degrees.