Dissertations / Theses on the topic 'Environmental biogeochemistry'
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Frost, Thomas. "Environmental controls of air-water gas exchange." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299423.
Full textRebecca, Steely L. "BIOGEOCHEMISTRY OF LAKE ERIE SEDIMENT AND PORE WATER." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1429549600.
Full textPark, Eun Joo. "Metal Speciation, Mixtures and Environmental Health Impacts." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23205169.
Full textMorrissey, Ember. "Environmental regulation of tidal wetland microbial communities and associated biogeochemistry." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3300.
Full textZang, Xu. "Encapsulation of Proteinaceous materials in Macromolecular Organic Matter as a mechanism for environmental preservation /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486400446370061.
Full textLi, Miling. "Environmental Origins of Methylmercury in Aquatic Biota and Humans." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:27201754.
Full textBlodau, Christian. "Carbon biogeochemistry in northern peatlands : regulation by environmental and biogeochemical factors." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38154.
Full textThe vegetation assimilated most of the deposited nitrogen and sulfate when water table levels were high. Lowered water table levels resulted in seepage of sulfate to the water table, reduced the rates of photosynthesis, and increased the soil respiration rates. The potential for sulfate reduction was fairly large, despite small in situ sulfate concentrations, and the CO2 production could not be fully accounted for by known processes. Potential rates of sulfate reduction were large both in samples taken from the field site and from the controlled experiments. SO42- addition resulted partly in stimulation, partly in reduction of potential CH4 production rates suggesting that the relationship between sulfate reduction and methanogenesis is not exclusively competitive.
Changes of the water table level had in situ effects on CO2 and CH4 production rates not explainable by a distinction in aerobic/anaerobic conditions. Anaerobic in situ rates at greater depths were much lower when the water table was at the surface of the mesocosms than when it was at greater depths. This might have been due to in situ accumulation of CO2 and CH 4 in the deeper peat, which lowers the energy gain of anaerobic C mineralization. Flooding and draining of peat soil resulted in a delayed onset of CH 4 production, in increased anaerobic CO2 production and decreased CH4 production rates, and in the decoupling of gas exchange from production rates. These results document that fluctuations of environmental variables on short time scales have an impact on rates of C turnover in peat soils, and also limit the predictability of fluxes by statistical models.
Dias, Isobelle A. "The environmental biogeochemistry of open ocean and partially enclosed marine systems." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303738.
Full textAmasah, Reda. "Studies on the environmental microbiology and biogeochemistry of desert surface soils." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2769/.
Full textJuice, Stephanie. "The Environmental Microbiome In A Changing World: Microbial Processes And Biogeochemistry." ScholarWorks @ UVM, 2020. https://scholarworks.uvm.edu/graddis/1181.
Full textMarois, Darryl Evan. "Modeling Wetland Biogeochemistry and Restoration in South Florida." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437578127.
Full textSelvendiran, Pranesh. "The role of small wetlands and lakes in transformation and transport of total and methyl mercury in the Adirondacks." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2009. http://wwwlib.umi.com/cr/syr/main.
Full textHindle, Kristi Marie. "The influence of wetting and drying cycles on the biogeochemical dynamics of mercury in sediments." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/26924.
Full textChoy, Emily Sarah. "Biotransport of organic contaminants and mercury to a coastal food web in the Canadian High Arctic." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28168.
Full textFathi, Mahsa. "Benthic flux of mercury between sediments and the overlying water in the St Lawrence River near Cornwall, Ontario." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28181.
Full textBellehumeur, Karyne M. F. "Consequences of Sublethal Polychlorinated Biphenyl Exposure on the Swimming Performance of Rainbow Trout Oncorhynchus mykiss." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28868.
Full textWang, Yi 1969. "Simulation of the climate, ocean, vegetation and terrestrial carbon cycle in the holocene." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86064.
Full textThe first application, in which the atmospheric CO 2 is fixed at 280 ppmv, shows that the vegetation-albedo feedback together with the retreating LIS allows the global annual mean surface air temperature to increase starting from 8 kyr BP and reach a maximum at around 6 kyr BP. The decreasing Northern Hemisphere summer insolation (orbital forcing) together with the vegetation-albedo feedback can explain the gradual cooling during the past 6 kyr. The southward shift of the boreal forest treeline from 6 to 0 kyr BP and the desertification of northern Africa from 8 to 2 kyr BP are also simulated, in good agreement with paleoclimatic reconstructions.
In the second application, the reconstructed (Taylor Dome) atmospheric CO2 is used as a variable radiative forcing, and an inverse method is introduced to investigate the global carbon cycle dynamics. The model results indicate that the retreating LIS, in association with the vegetation-albedo and vegetation-precipitation (biogeophysical) feedbacks, causes the terrestrial carbon store to reach its maximum at around 6 kyr BP. Based on the inverse method, it is inferred that the first 10 ppmv atmospheric CO 2 increase from 8 to 6 kyr BP comes from the ocean carbon pool, which includes sedimentation processes. However, the land carbon release of about 68 PgC (95 PgC without CO2 fertilization) from 6 to 0 kyr BP can only contribute about 5 to 7 ppmv increase in atmospheric CO2; additional carbon sources are needed from the ocean. The simulated desertification results in a 70-PgC decrease in total carbon in the Sahara desert. This decrease is partially compensated by a 40-PgC increase in total carbon in the Southern Hemisphere.
Finally, in the third application, the total volume of meltwater/freshwater from the retreating LIS is estimated, and four discharge scenarios are proposed to investigate the impact of this freshwater on the Holocene ocean, climate and terrestrial carbon cycle. During each freshwater perturbation, the simulated maximum Atlantic meridional overturning circulation (MOC) intensity is reduced, by amounts of up to 8 Sv. However, it rebounds to a higher level than the original state, within 10 to 20 years after the termination of the freshwater input. During the time of a weakened MOC, the SST is reduced in the high-latitude North Atlantic and increased in the Southern Ocean due to decreased northward oceanic heat transport. Only a large freshwater perturbation (>0.1 Sv) has a significant impact on the Holocene climate and terrestrial carbon cycle; it results in an enhanced cooling of about 1°C in the Northern Hemisphere (caused by the appearance of the North Atlantic sea ice) and notable drops in the global net primary productivity (2 PgC/yr) and total land carbon storage (40 PgC).
Akala, Vasant Arul. "Soil organic carbon sequestration in a reclaimed mineland chronosequence in Ohio." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1371219427.
Full textDavis, Thomas Andrew. "Cadmium biosorption and selectivity of sargassum spp. and their alginates in relation to their [alpha]-L-guluronic acid content and conformation." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82851.
Full textThe 1H-NMR characterization of the alginates, extracted from Sargassum by the modified method, reveals a consistent and unusual enrichment in homopolymeric alpha-L-guluronic acid (G-blocks). These alginates display G-block diad frequency values (FGG) between 0.37 and 0.81. This translates into an enhanced selectivity for cadmium and calcium relative to monovalent ions such as sodium and the proton as well as smaller divalent ions such as magnesium. Results of competitive exchange experiments in the Cd-Ca-alginate system yield selectivity coefficients, K* CdCa, between 0.43 +/- 0.10 and 1.32 +/- 0.02 for a range of FGG, from 0.23 to 0.81. In contrast, much larger selectivity coefficients were obtained for the Mg-Ca-alginate (K*MgCa ≤ 18.0 +/- 1.4) and Mg-Cd-alginate (K*MgCa ≤ 16.0 +/- 0.9) systems with alginates extracted from Sargassum fluitans (FGG = 0.81) and Sargassum thunbergeii (F GG = 0.75). Selectivity studies with mixed-metal pair alginate systems, as opposed to the more common single metal methods, highlight the importance of the specific macromolecular conformation of the alginate polymer in determining metal binding behaviour in multiple-metal systems as well as the performance of Sargassum as an algal biosorbent. The unique composition of the alginates present in species of Sargassum and the resilience of the algae to degradation provide this bio-material with a distinct advantage over other brown algal species when considering its implementation for the strategic removal of toxic heavy metals from contaminated and industrial waste waters.
Kausch, Matteo Francesco. "From Soil Aggregate to Watershed, from California's Central Valley to the Salton Sea -- Contamination across Ecosystems, Scales, and Disciplines." Thesis, University of California, Berkeley, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3616371.
Full textSelenium (Se) is a trace element of great ecological importance whose environmental distribution is highly impacted by anthropogenic activity. In the 1980s, selenium was recognized as a major aquatic contaminant following widespread deformities and mortality among waterfowl hatchlings near the agricultural drainage evaporation ponds of the Kesterson Reservoir (CA, USA). Today, 400,000 km2 in the Western United States are threatened by agricultural selenium contamination, as are parts of Canada, Egypt, Israel, and Mexico. From the soil aggregate to the watershed, from the soils of the Central Valley to the sediments of the Salton Sea, and from Environmental Science to Policy and Management, in this dissertation I explore agricultural selenium contamination across scales, ecosystems, and disciplines. I begin with a review of the science, policy, and management of irrigation-induced selenium contamination in California, the heart of worldwide research on the issue. I then delve into the physical and biogeochemical mechanisms that control selenium reduction and mobility within the structured surface soils that are the source of contamination, using an aggregate-scale combined experimental and reactive transport modeling approach. Finally, I present a diagenetic model for selenium incorporation into the sediment of the Salton Sea, which has been receiving seleniferous agricultural drainage over the last 100 years.
To extract lessons from the last 30 years of seleniferous drainage management and water quality regulation in California, I reviewed the history and current developments in science, policy, and management of irrigation-induced selenium contamination in California. Specifically, I evaluated improvements in the design of local attenuation methods and the development of programs for selenium load reductions at the regional scale. On the policy side, I assessed the site-specific water quality criteria under development for the San Francisco Bay-Delta in the context of previous regulation. This approach may be a landmark for future legislation on selenium in natural water bodies and I discussed challenges and opportunities in expanding it to other locations such as the Salton Sea. By combining proven management tools with the novel, site-specific policy approach, it may be possible to avoid future events of irrigation-induced selenium contamination. However, the majority of regional selenium load reductions in California were achieved by decreasing drainage volume rather than selenium concentrations. Thus, there appear to be opportunities for additional improvements through management practices that enhance selenium retention in source soils.
To quantify the likely implications of these experimental results for soils with different degrees of aggregation, I formulated a general mechanistic framework for aggregate scale heterogeneity in selenium reduction. Specifically, I constructed a dynamic 2D model of selenium fate in single idealized aggregates, in which reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se-species (selenate, selenite, and elemental selenium). The spatial and temporal dynamics of the model were validated with the experimental data and predictive simulations were performed covering aggregate sizes between 1 and 2.5 cm diameters. Simulations predict that selenium retention scales with aggregate size. Depending on aeration conditions and the input concentrations of selenate and pyruvate, selenium retention was predicted to be 4-23 times higher in 2.5-cm-aggregates compared to 1-cm-aggregates. Under oxic conditions, aggregate size and pyruvate-concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on seleniferous agricultural soils may thus help decrease the impacts of selenium contaminated drainage on downstream aquatic ecosystems receiving it.
This work presents agricultural selenium contamination as a complex problem that crosses ecosystems, scales, and disciplines. From a management perspective, the tension between dispersed non-point sources and hotspots where elevated selenium concentrations and sensitive aquatic ecosystems converge is difficult to address. Differences in biogeochemical conditions and trophic transfer within food webs render traditional regulatory approaches ineffective and force regulators to engage with the science of site-specific selenium transfer between ecological compartments. At the same time, gaps still exist in our mechanistic understanding of selenium's environmental cycling and in our integration of scientific knowledge across different ecosystems and scales. Centimeter scale heterogeneity in the biogeochemical conditions within source soils may fundamentally control selenium emissions across large agricultural areas and thus determine the selenium loading of rivers, lakes, and estuaries. Within aquatic environments receiving seleniferous drainage, the first few centimeters of surface sediment may control selenium exposure for entire food webs. Improved understanding at this level holds the potential to simultaneously reduce selenium emissions and respond more effectively to pollution where it occurs. In order to preserve sensitive habitat while also meeting agricultural drainage needs in seleniferous regions we must bridge the gaps between ecosystems, scales, and disciplines.
(Abstract shortened by UMI.)
Pedicino, Lisa Christine 1973. "Carbon isotopic variations in 7 southwestern United States plants from herbarium collections of the last 150 years." Thesis, The University of Arizona, 1997. http://hdl.handle.net/10150/291639.
Full textHua, Yujie. "Changes of Soil Biogeochemistry under Native and Exotic Plants Species." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1912.
Full textPulchan, K. Jerry. "Environmental biogeochemistry of the Northwest Arm and Trinity Bay, Newfoundland : novel molecular and carbon isotopic approaches /." Internet access available to MUN users only, 2001. http://collections.mun.ca/u?/theses,33207.
Full textWabomba, Mukire John. "Signal and Image Processing Techniques for Environmental and Clinical Applications of Infrared Spectroscopy." Ohio University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1040131767.
Full textGoodwin, David Hays. "Stable isotope and sclerochronologic analysis of environmental and temporal resolution in modern and fossil bivalve mollusk shells." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280282.
Full textDirghangi, Sitindra Sundar. "An Evaluation of the Environmental and Biological Controlling Factors of Lipid-Based Climate Proxies." Thesis, Yale University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3578331.
Full textLipids preserved in soils and sediments are important proxies in paleoclimate research. However, various growth conditions that affect the organisms synthesizing the lipids can in turn affect the abundance and stable isotopic compositions of the lipids themselves, and, consequently, can introduce significant errors in the paleoclimatic inferences drawn from them. This work examines how two climate proxies based on lipids, namely, glycerol dialkyl glycerol tetraether (GDGT)-based paleotemperature proxies in soils, and paleohydrological proxies based on hydrogen isotopic composition of lipids, respond to variability in environmental and other growth conditions (e.g., carbon source).
In order to evaluate the role of annual precipitation amount on the distribution of soil GDGTs and on GDGT-based temperature proxies in soils, we studied GDGT distribution in soils collected from two environmental transects in the USA—a dry, western transect covering six western states and a wet, east coast transect from Maine to Georgia. Our results indicate a significant impact of precipitation amount on soil GDGT distribution, which is related to soil aeration that in turn depends on precipitation amount, and also to soil pH. Our results also indicate that below an annual precipitation of 700-800 mm yr–1 the MBT/CBT-temperature proxy based on soil GDGTs is not applicable. Furthermore, due to the distinct GDGT distributions in soils under arid conditions, soil input into lacustrine or marginal marine environments cannot be estimated using BIT index.
In order to estimate the effects of variability in environmental conditions and utilization of different substrates on D/Hlipid, we studied two heterotrophic organisms—Haloarcula marismortui, a halophilic archaeon and Tetrahymena thermophila, a ciliated protozoan, in pure cultures. Our results from experiments with H. marismortui indicate that metabolism of different substrates leads to formation of reducing agents (mainly nicotinamide adenine dinucleotide phosphate or NADPH) with distinct D/H signatures, which is reflected in the significant D/H variations in isoprenoidal lipids (ca. 100‰). Growth temperature affects growth rate as well as enzyme activities, and salinity of the growth media affects mainly growth rate of H. marismortui, and both cause similar variations in D/Hlipid (ca. 20-30‰) that are smaller compared to the substrate-effect. T. thermophila , on the other hand, responds to variations in growth temperature in a different manner. Isoprenoid and fatty acids synthesized by T. thermophila generally become more D-enriched with temperature increase. The isoprenoid ranges from being D-depleted to D-enriched relative to water with temperature increase, but the fatty acids do not display similar patterns. Our results from T. thermophila culture experiments indicate that temperature has a critical control on the D/H ratios of NADPH and possibly also intracellular water, due probably to temperature effects on processes that are related to growth and metabolism of T. thermophila.
Chen, Limin Driscoll Charles T. "Modeling the response of forest and aquatic ecosystems of northeastern United States to changes in atmospheric deposition." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2004. http://wwwlib.umi.com/cr/syr/main.
Full textCoby, Aaron J. "Microbial iron-(hydr)oxide reduction effects on zinc speciation and interactions with nitrate reduction /." [Bloomington, Ind.] : Indiana University, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3163021.
Full textSource: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0765. Adviser: Flynn W. Picardal. Title from dissertation home page (viewed Oct. 18, 2006).
August-Schmidt, Elizabeth Melissa. "Mechanisms of Community Assembly Beneath N-Fixing Trees in a Hawaiian Dry Woodland." Thesis, University of California, Santa Barbara, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13423031.
Full textNitrogen (N) fixing trees are commonly used to promote forest restoration in disturbed areas because they can quickly recreate forest canopy structure. That structure in turn is hypothesized to attract animal seed dispersers and create enough shade to reduce undesirable species (particularly grasses). Yet N-fixers tend to increase soil N availability, which could facilitate the spread of nitrophilous invasive species. This dissertation evaluates the long-term consequences for understory community composition of establishing three N-fixing tree species (Acacia koa, Sophora chrysophylla, and Morella faya) after exotic grass-fueled fire in the seasonally dry subtropical woodland in Hawaii. To understand the restoration potential of these species, I compared discrete single-species stands of N-fixing trees in burned areas to both an intact native woodland and burned, open sites with no tree cover. Although N-fixing species are often assumed to be ecologically similar, trait variation among N-fixing trees in this system was strong enough to differentiate understory communities among stands of the three N-fixer species. To understand the mechanisms driving differences in understory composition among site types, particularly among N-fixing trees, I characterized the abiotic environment created by these species in terms of light and N availability, both of which were important drivers of understory community composition. High light and N availability were associated with greater exotic species cover and unique exotic species. Surprisingly, N availability was highest and N cycled fastest beneath the relatively slow-growing S. chrysophylla despite having much lower litter-N inputs than the faster-growing A. koa and M. faya. In this study, fast N-cycling was associated with high specific leaf area, high foliar N content and low foliar lignin:N. These traits are consistent with fast leaf economic spectrum traits in the general ecological literature, but this approach has not previously been applied to distinguish among N-fixing trees. Native Hawaiian dry forest understory recovery, particularly that of woody species, was limited throughout the burned area regardless of canopy cover. To determine what limits native shrub recovery, I sampled the seed bank and recorded natural seedling germination. I also planted native seedlings into the understory of all site types and either removed or left intact the invasive grass grasses present in the understory. I found that native shrubs were limited by both seed availability and competition with exotic grasses. Although outplant survival did not vary by N-fixer species identity, differences in the mechanisms by which each N-fixing species limited native seedling survival likely play a role in understory community assembly long-term. When restoration occurs in the context of secondary succession, prioritizing the creation of forest structure using N-fixing trees, particularly open-canopied fast-cycling species, such as S. chrysophylla, could make full community recovery more difficult by promoting rather than suppressing exotic grasses.
Blankson, Emmanuel Robert. "The Effect of Bioturbation on Transport, Bioavailability and Toxicity of Lead (Pb) in Freshwater Laboratory Microcosms." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10163300.
Full textSediment bioturbators play an important ecological role and may both be affected by contaminants in the sediment and affect the fate and distribution of these contaminants. This is especially important for the many contaminants, like lead, for which sediments serve as a sink upon the contaminants’ release into the environment. In this study, I investigated the toxicity of sediment Pb to a freshwater bioturbator, the effect of bioturbation on the environmental distribution of the Pb, the effect of sediment characteristics on the bioturbation-mediated transfer of Pb from the sediment to the water column, and this transfer’s toxicological consequences for planktonic organisms. Experiments were conducted in microcosms with control sediment or Pb-spiked sediment, the freshwater oligochaete Lumbriculus variegatus served as the model bioturbator, and the water flea Daphnia magna served as the model planktonic organism. The rate of bioturbation of the oligochaete was quantified using luminophores.
The bioturbation resulted in the transfer of Pb from the sediment to the water column. However, it did not affect Pb levels in the worm tissue or in the sediment. The environmental distribution of Pb among water column, biota, and sediment in the presence of the bioturbator was dependent on sediment characteristic like organic content, silt/clay content, and the pH of the sediment. Bioturbation by L. variegatus increased bioaccumulation of Pb in D. magna; however, this Pb had no toxic effect on survival, reproduction, and biomass of D. magna under the specific conditions used here. Quantification of the bioturbation rates of L. variegatus showed that the intensity of the bioturbation was enhanced at higher densities of the oligochaete but reduced at high sedimentary Pb concentrations. Overall this study demonstrated that bioturbation by L. variegatus can transfer Pb from the sediment to the water column, and that this transfer is dependent on sediment characteristics. The Pb transferred as a result of the bioturbation can enhance Pb availability to organisms in the water column, and potentially cause toxic effects in these organisms.
McCaulou, Douglas Ray 1955. "The effects of temperature and motility on the advective transport of a deep subsurface bacteria through saturated sediment." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278312.
Full textLemon, Michelle M. "The effects of land use and regional hydrology on surface water quality in the upper San Pedro River, Arizona, United States of America." Thesis, The University of Arizona, 2004. http://hdl.handle.net/10150/292075.
Full textMitra, Siddhartha. "Polycyclic aromatic hydrocarbon (PAH) distributions within urban estuarine sediments." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539616779.
Full textWalker, Rachel Alex. "Methylmercury Bioaccumulation in Spotted Salamanders (Ambystoma maculatum) in Southern Ohio." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496084470204606.
Full textRichardson, Bree Lacey. "HYDROLOGICAL AND BIOGEOCHEMICAL MECHANISMS DRIVING NITROGEN AND PHOSPHORUS RETENTION IN A FRESHWATER ESTUARY." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1529269594773022.
Full textO'Driscoll, Nelson James. "Dissolved gaseous mercury dynamics and mercury volatilization in freshwater lakes." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/29035.
Full textSheremata, Tamara W. "The influence of soil organic matter on the fate of trichloroethylene in soil." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0017/NQ44582.pdf.
Full textBosch, Jennifer Anne. "Polychaetes, Hypoxia, and Nitrogen Cycling in the Mesohaline Chesapeake Bay." Thesis, University of Maryland, College Park, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3644071.
Full textBenthic macrofauna can play an important role in facilitating some of the microbial mediated processes of nitrogen cycling in estuarine sediments. Declines in benthic macrofauna, like polychaete worms, have been attributed to long-term increases in bottom water hypoxia in Chesapeake Bay. Utilizing a large monitoring dataset including benthic macrofaunal abundance, biomass, and concurrent measures of environmental parameters, I examined how environmental conditions regulate the densities of opportunistic polychaetes in a mesohaline estuarine system. This analysis points to a benthic community dominated by euryhaline, opportunistic polychaete worms (M. viridis, S. benedicti, H. filiformis, A. succinea) which have well adapted but varying responses to hypoxia and other stressful conditions. Results of two laboratory experiments with the opportunistic polychaete Alitta (Neanthes) succinea were used to quantify the short-term influence of density and size of surface-feeding polychaetes on sediment-water fluxes of inorganic nitrogen under varying oxygen conditions. Polychaete enhancements of O2 and nitrogen fluxes were strongly correlated with total animal biomass. Solute fluxes were stimulated by presence of both larger and smaller worms, but per capita effects were greater for the deep-burrowing larger polychaetes. Utilizing a unique large-scale monitoring dataset collected in the Chesapeake Bay, I employed Classification and Regression Tree (CART) and multiple linear regression (MLR) analyses to assess the relationship between benthic biomass and NH4 + efflux within different regions of the estuary by season. In addition to labile organic matter, oligohaline and mesohaline tributary temperature and salinity control the rate of nitrogen cycling and benthic macrofaunal biomass. In deeper regions of mesohaline tributaries and the mainstem Bay, dissolved oxygen was found to be the dominating parameter regulating sediment nitrogen pathways as well as the structure of the benthic macrofaunal community. With increased macrofaunal biomass, spring regressions indicated an enhancement of NH4+ efflux. In contrast, fall regressions indicated the enhancement of fixed nitrogen removal from sediments. Summer data lacked a significant relationship, but high NH4 + effluxes under hypoxic/anoxic conditions suggested dissolved oxygen is the primary driver of summer nitrogen cycling. This study, using field and laboratory data, concludes that a complex balance between seasonal and regional dissolved oxygen, temperature and salinity conditions shape not only the benthic community but also the relationship between macrofaunal biomass and sediment nitrogen flux in this eutrophic estuarine system.
Schiebel, Hayley Nicole. "Dissolved organic carbon fluxes from a New England salt marsh." Thesis, University of Massachusetts Boston, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10118488.
Full textBlue carbon systems (mangroves, salt marshes, and seagrass beds) sequester large amounts of carbon via primary productivity and sedimentation. Sequestered carbon can be respired back to the atmosphere, buried for long time periods, or exported (“outwelled”) to adjacent ecosystems. This study estimates the total outwelling of dissolved organic carbon (DOC) from the Neponset Salt Marsh (Boston, Massachusetts) as well as the major plant and sediment processes contributing to the overall flux. The total export was quantified via high-resolution in situ chromophoric dissolved organic matter (CDOM) measurements as a proxy for DOC using 12 years of transect data. Seasonal trends, alternate sources of fresh water, and long-term trends in DOC export will be discussed. To characterize the percentage of this flux attributable to marsh vegetation, the effects of sunlight, anoxia, plant species, biomass type, and microbes on plant leaching were studied using incubations of above- and belowground biomass over four seasons. Seasonal comparisons led to the “Fall Dump” hypothesis in which higher DOC concentrations are leached during the fall when marsh plants senesce for winter. In summing seasonal fluxes from vegetation, approximately 46% of the total DOC export from the marsh may be attributed to leaching from the three dominant plant species in the Neponset Salt Marsh. The influence of seasonality and climate change (e.g., drought) on both overland flow and deep sediment pore water leaching were also investigated. Depending on season and marsh condition, overland flow and sediment pore water leaching combined could contribute 8–16% of the total export from the marsh. Finally, the influence of natural sunlight irradiation and microbes on the release of dissolved organic matter (DOM) from resuspended surface sediments was studied and approximately 11–22% of the total export could be attributable to this flux. Approximately 49 mol C m−2 yr−1 are outwelled from the Neponset Salt Marsh and, using net primary productivity estimates from the literature, 16 ± 12 mol C m −2 yr−1 are buried in the Neponset Salt Marsh.
Arzayus, Krisa Murray. "Fate of organic compounds associated with extractable and bound phases of estuarine sediments deposited under varying depositional regimes." W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539616552.
Full textWang, Jiann-Ming. "Intrinsic and enhanced biodegradation of polyaromatic hydrocarbons in aqueous and soil systems." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284046.
Full textKambis, Alexis Demitrios. "A numerical model of the global carbon cycle to predict atmospheric carbon dioxide concentrations." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539616709.
Full textVenkatraman, Padma T. "Persistent organic pollutant transport and fate: Assessment by molecular tracers." W&M ScholarWorks, 2001. https://scholarworks.wm.edu/etd/1539616891.
Full textPerez, Rojas Nadejda. "Biogeochemistry of iron and phosphorus in soils impacted by penguin colonies in Antarctica." Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27646.
Full textPalmer, Sheila Mary Johnson Chris E. "Spatial and temporal patterns in the biogeochemistry of aluminum at the Hubbard Brook Experimental Forest, New Hampshire." Related Electronic Resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2003. http://wwwlib.umi.com/cr/syr/main.
Full textMeyer, Amanda Lynn. "Biogeochemistry of Sulfur Isotopes in Crystal Lake, Clark County, West-Central Ohio." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1420911116.
Full textSadurski, Stephen Edward. "The Biogeochemistry of Carbon Isotopes in Local Lakes." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1357745315.
Full textDouglass, James G. "Community dynamics in submersed aquatic vegetation: Intermediate consumers as mediators of environmental change." W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539616634.
Full textBarral, Fraga Laura. "Arsenic and fluvial biofilms: biogeochemistry, toxicity and biotic interactions." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/461201.
Full textBasándonos en los conocimientos actuales sobre la ecotoxicología del biofilm y la biogeoquímica del arsénico en ecosistemas dulceacuícolas, esta tesis estudió, bajo concentraciones ambientales realistas, i) el papel de los biofilms bentónicos en la biodisponibilidad y destoxificación del arsénico, ii) los efectos tóxicos del arsénico sobre la estructura y función de los biofilms bentónicos fluviales, prestando especial atención a las respuestas de las diatomeas, y iii) la interacción entre estos productores primarios y organismos superiores como los peces, expuestos a arsénico. El arsénico inhibió el crecimiento algal, pudiendo las diatomeas adaptarse mediante una significativa reducción de su biovolumen celular (capítulo 1). El biofilm agravó los efectos del arsénico en peces (capítulo 2) pero también fue capaz de destoxificar metilando especies inorgánicas de arsénico (capítulo 3). Los resultados de esta tesis proporcionan información valiosa para comprender la contribución de los biofilms a la biogeoquímica y toxicidad del arsénico en sistemas dulceacuícolas.
CAT: S'han extret de la tesi doctoral el contingut del cap. 1 General introduction i Cap. 4 General discussion; part del capítol 3 que inclouen articles en preparació. També s'han extret els Annexos 1 i 2 que incloïen els pdf editor d'articles ja publicats.----- ENG: The content of Chapter 1. General introduction and Chapter 4 General discussion; part of Chapter 3 that have articles in preparation have been extracted from the doctoral thesis pdf. Appendices 1 2 that included the pdf editor of articles already published have been extracted from the doctoral thesis too.
Roebuck, J. Alan Jr. "Environmental Dynamics of Dissolved Organic Matter and Dissolved Black Carbon in Fluvial Systems: Effects of Biogeochemistry and Land Use." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3755.
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