Dissertations / Theses on the topic 'Biogeochemistry'
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Mortimer, Robert J. G. "Biogeochemistry of iron." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262558.
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Guicharnaud, Rannveig A. "Biogeochemistry of Icelandic Andosols." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Online version available for University member only until July 1, 2014, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=53377.
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Guido-Garcia, Fabiola. "The biogeochemistry of iodine." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-biogeochemistry-of-iodine(031a6229-1a96-4068-9764-8291bafb0cad).html.
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Iodine-129 is a high-yield fission product of 235U and 239Pu; is produced in nuclear power plants and is therefore present in substantial quantities in radioactive wastes. In the environment, iodine exists as a range of species: iodate (IO3-), iodide (I-), elemental iodine (I2), HOI and organic species are the most common. The behaviour of iodine in the environment is linked to its speciation which can be affected by different factors such as pH, redox potential and enzymatic reduction. Previous research has shown that iodine speciation can determine its fate in the environment; however the mechanisms of redox cycling amongst the different species are not yet fully understood. This research project has focused on improving the understanding of the changes on speciation of iodine in sediment and mineral systems undergoing redox cycling reactions. The fate and changes in iodine speciation were studied under reducing and oxidising conditions, with all experiments conducted under circumneutral pH conditions. Overall the results showed that when microbial activity is promoted in a sediment system, iodate is reduced to iodide with the reduction occurring during manganese reduction. Further, when nitrate is present at high concentrations the reduction of iodate is retarded. A net release of native iodine from sediments was observed in all experiments conducted with sediments; confirming previous observations that sediment bound iodine is released from sediments under reducing conditions. Modest abiotic reduction of iodate was observed under manganese and iron reduction; and iodate reduction happened faster in a mixed system with iron and pure culture bacteria than solely by the pure culture alone or via abiotic reduction with Fe(II). When reduced experiments were exposed to air, concentrations of iodide decreased with no iodate ingrowth or losses in total iodine in solution. This suggested that iodide had been oxidised to intermediate species (I2, HOI) that were not detected, although this reaction has been described in past research. Finally, when no microbial activity is promoted, iodine remains as iodate which showed modest sorption onto sediment systems and Fe(III) oxide. Overall, these results highlight the important role that bacteria play in the reduction of iodate. This research also confirms that iodine speciation impacts on the fate of 129I throughout the environment, where it may be less mobile in an oxic environment than under reducing conditions. Moreover, some techniques of bioremediation (e.g. promoting metal reducing conditions) may cause the release of radioactive iodine to solution.
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Jones, Charles Nathaniel. "Floodplain Hydrology and Biogeochemistry." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/75169.
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River-floodplain connectivity is defined as the water mediated transfer of materials and energy between a river or stream and its adjacent floodplain. It is generally accepted that restoring and/or enhancing river-floodplain connectivity can reduce the downstream flux of reactive solutes such as nitrogen (N) and phosphorus (P) and thus improve downstream water quality. However, there is little scientific literature to guide ecological engineering efforts which optimize river-floodplain connectivity for solute retention. Therefore, the aim of my dissertation research was to examine feedbacks between inundation hydrology and floodplain biogeochemistry, with an emphasis on analyzing variation experienced along the river continuum and the cumulative effects of river-floodplain connectivity at the basin scale. This was completed through four independent investigations. Field sites ranged from the Atchafalaya River Basin, the largest river-floodplain system in the continental US, to the floodplain of a recently restored headwater stream in Appalachia. We also developed a method to examine river-floodplain connectivity across large- river networks and applied that methodology to US stream network. Largely, our results highlight the role floodwater residence time distributions play in floodplain biogeochemistry. In headwater streams, residence times restrict redox dependent processes (e.g. denitrification) and downstream flushing of reactive solutes is the dominant process. However, in large-river floodplains, redox dependent processes can become solute limited because of prolonged residence times and hydrologic isolation. In these floodplains, the dominant process is often autochthonous solute accumulation. Further, results from our modeling study suggest large-river floodplains have a greater impact on downstream water quality than floodplains associated with smaller streams, even when considering cumulative effects across the entire river network.Ph. D.
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Dolor, Marvourneen Kimranee. "Investigation of Rhenium's biogeochemistry." College Park, Md. : University of Maryland, 2009. http://hdl.handle.net/1903/9260.
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Thesis (Ph. D.)--University of Maryland, College Park, 2009.Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Tuit, Caroline Beth 1973. "The marine biogeochemistry of molybdenum." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/58369.
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Thesis (Ph. D.)--Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, and the Woods Hole Oceanographic Institution), 2003.Includes bibliographical references.
Prevailing wisdom holds that the vertical distribution of molybdenum (Mo) in the open ocean is conservative, despite Mo's important biological role and association with Mn oxides and anoxic sediments. Mo is used in both nitrogenase, the enzyme responsible for N2 fixation, and nitrate reductase, which catalyzes assimilatory and dissimilatory nitrate reduction. Laboratory culture work on two N2 fixing marine cyanobacteria, Trichodesmium and Crocosphaera, and a marine facultative denitrifier, Marinobacter hydrocarbanoclasticus, showed that Mo cell quotas in these organisms were positively correlated with Mo-containing enzyme activity. Mo concentrations in Crocosphaera dropped almost to blank levels when not fixing N2 suggesting daily synthesis and destruction of the entire nitrogenase enzyme and release of Mo. Trichodesmium cultures, however, retained a pool of cellular Mo even when not fixing N2. Colonies of Trichodesmium collected in the field have Mo:C tenfold higher than seen in culture, these Mo:C ratios were reflected in SPM samples from the same region. Fe:C ratios for Trichodesmium were between 12-160 pmol:mol in field and culured samples. The Fe:C ratio of Crocosphaera was established to be 15.8 =/+ 11.3 under N2 fixing conditions. Mo cellular concentrations in cultured organisms were too small to significantly influence dissolved Mo distributions, but may slightly affect Suspended Particulate Matter (SPM) distributions. Mean SPM Mo:C ratios were slightly elevated in regions of N2 fixation and denitrification.. A high precision (=/+ 0.5%) isotope dilution ICP-MS method for measuring Mo was developed to re-evaluate the marine distribution of Mo in the dissolved and particulate phase.
(cont.) Mn oxides were not found to significantly influence either the dissolved or SPM Mo distribution. Dissolved Mo profiles from the Sargasso and Arabian Sea were conservative. However, dissolved Mo profiles from the Eastern Tropical Pacific showed both depletion and enrichment of dissolved Mo possibly associated with interaction of Mo with coastal sediments. Dissolved Mo profiles in several California Borderland Basins showed 1-2 nM Mo depletions below sill depth. A more focused study of water column response to sediment fluxes using the high precision Mo analyses is necessary to determine whether these phenomena are related.
by Caroline Beth Tuit.
Ph.D.
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Williford, Kenneth Hart. "Biogeochemistry of the Triassic-Jurassic boundary /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/6708.
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Clark, James Richard. "Individual-based modelling of marine biogeochemistry." Thesis, University of East Anglia, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539335.
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Moos, Simone Beatrice. "The marine biogeochemistry of chromium isotopes." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115788.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018.Cataloged from PDF version of thesis.
Includes bibliographical references.
In the ocean, chromium (Cr) is a redox-sensitive trace metal. The reduction of Cr(VI) to Cr(III) occurs in oxygen deficient zones (ODZs), and Cr reduction in general has been identified as a significant Cr isotope fractionation mechanism. This thesis presents the first Cr isotope variations (653 Cr) in ODZs of the ocean and adds to the sparse Cr isotope data published for modern seawater. I developed a precise and accurate Cr isotope method for seawater samples. Seawater acidification converts total Cr to Cr(III) which is preconcentrated by Mg(OH) 2 coprecipitation. A three-column anion exchange chromatography scheme separates Cr from isobaric and polyatomic interferences present in the seawater and reagent matrixes. Isotope analysis is performed on a MC-ICP-MS IsoProbe. The addition of a 50Cr-54Cr double spike allows for accurate correction of procedural and instrumental Cr mass fractionations. The first Cr isotope ratio data for a full water column profile in the Pacific Ocean is presented. This station serves as a fully oxic counterpart to stations located within the ODZ of the Eastern Tropical North Pacific. At one station, Cr concentrations are lower and [delta]53Cr values are heavier within the ODZ. This is consistent with Cr reduction resulting in isotopically lighter, particle-reactive Cr(III), which is scavenged and exported from the water column. A strong correlation of [delta]53Cr and [delta]15 NNo3- at this station suggests that Cr reduction may be microbially mediated instead of simply being a product of thermodynamic equilibrium. Alternatively, Cr may be reduced by Fe(II). In the anoxic bottom waters of the Santa Barbara Basin a strong Cr reduction signal (lower [Cr], heavier [delta]53Cr) is observed, which may result from the same aforementioned Cr reduction mechanisms. A shift to the heaviest seawater Cr isotope signatures yet observed was detected in the oxic bottom waters of the shallow Arctic Chukchi shelf, while Cr concentrations decreased. This extreme isotope signal may result from Cr reduction by a reduced species (e.g. Fe(II)), which was released from the underlying anoxic shelf sediments. Cr in the Atlantic layer and in the bottom water of a central Arctic station appears to be shaped by a novel, unidentified process.
by Simone Beatrice Moos.
Ph. D.
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John, Seth G. "The marine biogeochemistry of zinc isotopes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40968.
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Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007.Includes bibliographical references.
Zinc (Zn) stable isotopes can record information about important oceanographic processes. This thesis presents data on Zn isotopes in anthropogenic materials, hydrothermal fluids and minerals, cultured marine phytoplankton, natural plankton, and seawater. By measuring Zn isotopes in a diverse array of marine samples, we hope to understand how Zn isotopes are fractionated in the oceans and how Zn isotopes may be used as tracers of marine biogeochemical processes. Common forms of anthropogenic Zn had [delta]66Zn from +0.08 %o to +0.32 %o, a range similar to Zn ores and terrigenous materials. Larger variations were discovered in hydrothermal fluids and minerals, with hydrothermal fluids ranging in 666Zn from 0.02 %o to +0.93 %o, and chimney minerals ranging from -0.09 %o to +1.17 %o. Lower-temperature vent systems had higher [delta]666Zn values, suggesting that precipitation of isotopically light Zn sulfides drives much of the Zn isotope fractionation in hydrothermal systems. In cultured diatoms, a relationship was discovered between Zn transport by either high-affinity or low-affinity uptake pathways, and the magnitude of Zn isotope fractionation. We established isotope effects of [delta]66Zn = -0.2 %o for high-affinity uptake and [delta]66Zn = -0.8 %o for low-affinity uptake. This work is the first to describe the molecular basis for biological fractionation of transition metals. Biological fractionation of Zn isotopes under natural conditions was investigated by measuring Zn isotopes in plankton collected in the Peru Upwelling Region and around the world.
(cont.) Seawater dissolved Zn isotopes also reflect the chemical and biological cycling of Zn. The [delta]66Zn of deep seawater in the North Pacific and North Atlantic is about 0.5%0, and the dissolved [delta]66Zn gets lighter in the upper water column. This is unexpected based our observations of a biological preference for uptake of light Zn isotopes, and suggests that Zn transport to deep waters may occur by Zn adsorption to sinking particles rather than as primary biological Zn. The thesis, by presenting data on several important aspects of Zn isotope cycling in the oceans, lays the groundwork for further use of Zn isotopes as a marine biogeochemical tracer.
by Seth Greeley John.
Ph.D.
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Frame, Caitlin H. "The biogeochemistry of marine nitrous oxide." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68887.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), June 2011."June 2011." Cataloged from PDF version of thesis.
Includes bibliographical references.
Atmospheric nitrous oxide N₂O concentrations have been rising steadily for the past century as a result of human activities. In particular, human perturbation of the nitrogen cycle has increased the N₂O production rates of the two major sources of this greenhouse gas, soil and the ocean. Nitrification, and particularly ammonia oxidation, is one of the major processes that produces N₂O in the ocean. In this thesis, a series of stable isotopic methods have been used to characterize the biogeochemical controls on N₂O production by marine nitrification as well as the natural abundance stable isotopic signatures of N₂O produced by marine nitrifiers. This thesis shows that in addition to chemical controls on N₂O production rates such as oxygen (O₂) and nitrite (NO₂- ) concentrations, there are also biological controls such as nitrifier cell abundances and coastal phytoplankton blooms that may influence N₂O production by ammonia oxidizers as well. Ammonia oxidizers can produce N₂O through two separate biochemical mechanisms that have unique isotopic signatures. Using culture-based measurements of these signatures, we conclude that one of these pathways, nitrifier-denitrification, may be a significant source of N₂O produced in the South Atlantic Ocean and possibly the global ocean.
by Caitlin Frame.
Ph.D.
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Nielsdóttir, Maria Chun. "Iron biogeochemistry in (sub-) Polar waters." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/145859/.
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Iron represents an important control on primary production in high nutrient low chlorophyll (HNLC) regimes and has received considerably attention during the last two decades. This work has focussed on the biogeochemistry of iron in two oceanic environments; the high latitude North Atlantic and the Scotia Sea in the Southern Ocean. The mechanisms of iron supply and the biological response of resident phytoplankton communities to iron were addressed in both study areas. Two cruises to the high latitude North Atlantic Ocean (>55 °N) during late July-early September 2007 indicated that nitrate concentrations of 2 to 5 M persisted in the surface waters. The concentration of dissolved iron (dFe) in the surface waters was very low, with an average of 0.093 (<0.010-0.218, n=43) nM, and in situ chlorophyll concentrations were < 0.5 mg m-3. In vitro iron addition experiments demonstrated that the addition of iron increased photosynthetic efficiencies (Fv/Fm) and resulted in enhanced chlorophyll in treatments amended with iron when compared to controls. A number of phytoplankton taxa, including the coccolithophore Emiliania huxleyi, were observed to increase their net growth rates following iron addition. These results provide strong evidence that iron limitation within the post spring bloom phytoplankton community contributes to the observed residual macronutrient pool during summer. Low atmospheric iron supply and suboptimal Fe:N ratios in winter overturned deep water are suggested as proximal causes for this seasonal High Nutrient Low Chlorophyll (HNLC) condition, which represents an inefficiency of the biological (soft tissue) carbon pump. Large areas of the Southern Ocean are characterised as HNLC. Satellite chlorophyll data indicate that phytoplankton blooms occur in vicinity to Southern Ocean Island systems. The bloom associated with South Georgia has the largest spatial extent and duration (16-20 weeks). Detailed measurements were made on austral spring and summer cruises to the Scotia Sea during November – early December 2006 and January – February 2008. This work presents the first comprehensive study of seasonal variations in phytoplankton biomass and iron availability in the Scotia Sea. The drawdown of nitrate between the two seasons in the South Georgia bloom was 16 M indicative of substantial new production. Surface water concentrations of dissolved iron (dFe) were slightly higher during summer than spring (0.31 nM compared to 0.20 nM, with P>0.05). We suggest that the South Georgia bloom is sustained by a continuous benthic supply of iron from the South Georgia shelf. In addition, enhanced dFe (0.34 nM) was observed in a cryptophyte dominated bloom in the southern Scotia Sea in the vicinity of South Orkney Islands. The difference in the community composition between the two natural occurring blooms highlight that Southern Ocean island systems have individual characteristics and should be viewed independently.
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Thorpe, Clare. "The biogeochemistry of radioactively contaminated land." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/the-biogeochemistry-of-radioactively-contaminated-land(6407b765-9638-4707-8f7d-ef93bf603726).html.
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A global legacy of radioactively contaminated land exists as a result of nuclear fuel cycle operations. Demonstration of the safe management of the UK nuclear legacy, including contaminated land, is important whilst the long term fate of legacy waste remains uncertain and the UK is moves towards new nuclear power. One aspect of nuclear contaminated land research focuses on the immobilisation of intermediate and long lived radionuclides that are mobile in groundwater and are migrating in the environment. At Sellafield nuclear facility, UK, strontium-90 and technetium-99 are found as co-contaminants in groundwater alongside the most abundant non radioactive contaminant, nitrate. Their differing radiochemical behaviour and the presence of nitrate presents a challenge for remediation strategies. Bioremediation has the potential for in-situ immobilization of 99Tc via reduction from mobile Tc(VII) to less mobile Tc(IV) concurrent with Fe(III) reduction. In this project bioreduction processes were investigated in sediment microcosms and model systems under variable pH and nitrate conditions and using microorganisms representative of the Sellafield site. Sediment bioreduction occurred via stimulation of the natural microbial community. Denitrification resulted a delay in the onset of metal reduction followed by a raised pH. At the mildly acidic pH of the natural sediments, a nitrate concentration of 100 mM caused bioreduction to stall. However, at pH 7, reduction of 100 mM nitrate resulted in a final pH > 9 and alkaline Fe(III) reduction. In bioreduced sediments, the microbial ecology was dominated by nitrate reducing microorganisms and Fe(III) reducing enrichment cultures were necessary to identify relevant alkaline Fe(III) reducing bacteria. Enrichment cultures isolated a novel alkali tolerant Fe(III) reducing Serratia sp. with a growth range of pH 4 to 9. Increased pH resulting from denitrification decreased the mobility of Sr2+ via increased sorption to mineral surfaces. X-ray absorption spectroscopy confirmed Sr2+ incorporation into carbonate mineral phases above pH 8.5. Model systems showed reductive removal of 99Tc from solution by an Fe(II) bearing mineral assemblage at both pH 7 and 9. In contrast Sr2+ remained in solution at pH 7 and precipitated as SrCO3 at pH > 8.5. This study for the first time demonstrates the effects of high nitrate on pH in Sellafield type sediments, alkaline Fe(III) reduction by a Serratia sp, the incorporation behaviour of Sr2+ during sediment bioreduction and the behaviour of Sr2+ and 99Tc in novel Fe(II) mineral bearing model systems. These findings improve the understanding of radionuclide migration at contaminated sites and inform possible engineered bioremediation scenarios.
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Pabi, Sudeshna. "Carbon biogeochemistry in the polar oceans /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Boonchayaanant, Benjaporn. "Biogeochemistry of uranium reduction and reoxidation /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Keith-Roach, Miranda. "The biogeochemistry of the transuranium elements." Thesis, University of Manchester, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669532.
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Begg, James David. "Radionuclide biogeochemistry in UK contaminated land scenarios." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491755.
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Technetium and uranium are radionuclides found in groundwaters at sites where nuclear wastes have been processed or stored. As a result, increasing understanding of the mobility of these radioactive contaminants in the environment is required in order to predict their movement in the sub-surface and to develop efficient remediation of contaminated environments. The redox chemistry of both technetium and uranium exerts a strong control on their environmental behaviour. Unde~ oxic conditions, mobile Tc(VII) and U(VI) species dominate. In contrast, under reducing conditions the Tc(IV) and U(IV) oxidation states predominate and are poorly soluble. A change in oxidation state of both Tc and U can be effected by indigenous microbial activity in natural soils and sediments. As a result, indigenous microbes may play an important role in controlling the environmental behaviour of both these redox active radionuclides. Here, a multidisciplinary approach is applied in order to identifY biogeochemical factors that control the redox state and environmental behaviour of Tc and U in soil from the UKAEA operated site at Dounreay, UK. Microcosm experiments containing soil from the site' at Dounreay showed that indigenous microbial activity caused removal of Tc(VII) from solution during anaerobic incubation and was most likely mediated by '~'-------abiotic~reauCtiori-of-Tc(VII)-wiih microbially -pro-dilced---Fe(II).--X,:ray -absc)rptiori--------------- spectroscopy (XAS) analysis confirmed reduction of Tc(VII) to Tc(IV) in microcosm experiments. Tc was found to be partially remobilised following exposure of reduced Tc(IV)-labelled soils to _air, but was not significantly remobilised following exposure to nitrate. In uranium experiments, uptake of U(VI) by soil was rapid and complete under oxic conditions from artificial groundwater and in experiments with groundwater amended with ethylenediaminetetraacetic acid (EDTA). By contrast, uptake was slower in systems amended with bicarbonate. XAS experiments confirmed that uranium was adsorbed to soil as U(VI) in all three groundwater systems. After anaerobic. incubation for 120 days and the development of microbially-mediated Fe(III)- and sol- reducing conditions, XAS analysis showed that soil-associated uranium was present as U(IV) in all three systems. Further investigation of unamended artificial groundwater systems indicated that reduction of sorbed U(VI) required an active microbial population. These findings suggest that indigenous soil microorganisms in a Dounreay-type soil environment will exert a strong control on the fate ofTc and U.
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Dean, Rebecca J. "Biogeochemistry of metals in fish farm sediments." Thesis, Open University, 2005. https://pure.uhi.ac.uk/portal/en/studentthesis/biogeochemistry-of-metals-in-fish-farm-sediments(846eb31f-5004-4e3a-8f99-804bb47e415c).html.
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Salmon farming is a major industry in many Scottish sea lochs. Although the impact of salmon farming and pathways of several farm wastes have been studied extensively, there has been little research into the fate of metals originating from fish farms. This thesis investigates the influence of salmon farming on sediment biogeochemical conditions, with particular reference to the cycling, interactions, and effects of metals in farm sediments of Scottish sea lochs. Scottish sea lochs are fjordic systems, and have a defined set of physical processes occurring within them that depend on topographical characteristics of the sea loch and the influence of external forces. The most common definition of a fjord, also know as a sea loch, is “a deep, high-latitude estuary which has been (or is presently being) excavated or modified by landbased ice” (Syvitski et al. 1987). The established opinion of their origin is that fluvial action along fault lines allowed subsequent glaciers to follow this path of least resistance, leading to major excavation (Skei et al. 2003). Fjords are found in all northern and southern regions of the earth that were once ice-covered, but this review will focus on the sea loch (fjordic) systems of western Scotland.
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Bechtold, James Scott. "Fluvial sediment influences on floodplain soil biogeochemistry /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5358.
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Yeh, Chen-Ying. "The biogeochemistry of dimethylsulphoniopropionate in estuarine sediments." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327256.
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Ohnemus, Daniel Chester. "The biogeochemistry of marine particulate trace metals." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87512.
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Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Marine particles include all living and non-living solid components of seawater, representing an extremely dynamic and chemically diverse mixture of phases. The distributions of these phases are poorly constrained and undersampled in the oceans, despite interactions between living organisms and non-living minerals having central roles within many globally relevant biogeochemical processes. Through a combination of method development, basin-scale particulate collection and analyses, modeling, and field experiments, this thesis examines both the distributions of marine particulate trace metals and the underlying processes-inputs, scavenging, vertical and horizontal transport, and biotic uptake-in which marine particles participate. I first present the results of an intercalibration exercise among several US laboratories that analyzed filtered particles on shared polyethersulfone filters. We use inter-lab and intra-lab total elemental recoveries of these particles to determine our state of our intercalibration (by Daniel Chester Ohnemus.
Ph. D.
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Naude, Minette. "Fynbos riparian biogeochemistry and invasive Australian acacias." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20325.
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Thesis (MScConEcol)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Riparian ecotones, transitional areas between upland terrestrial communities and aquatic ecosystems, are very dynamic and complex ecosystems with intrinsic ecological properties differing in spatial structure, function and temporal dynamics. Riparian habitats along rivers of the Mediterranean south-western Cape are sensitive to environmental change and particularly vulnerable to invasion by invasive alien plants (IAPs), especially nitrogen-fixing Acacia spp., and yet relatively little work has focused on how riparian ecosystems in this region respond to such stressors. The important roles that intact riparian vegetation play in maintaining ecosystem integrity and services have been increasingly highlighted as we acknowledge the degradation of these habitats. While the Working for Water (WfW) programme has been shown to be very successful in eradicating IAPs in riparian zones in the short-term, the extent to which riparian ecosystems recover following alien clearing activities remains poorly understood. The results presented in this study addressed several different aspects of riparian structure and function and acts as a steppingstone for guiding future research and management in riparian zones by adding to the evaluation of the success of clearing initiatives and restoration thereof. The aim of this study was to assess plant functional type (PFT) cover, soil physical and chemical properties, and selected biogeochemical processes in natural, Acacia- invaded and cleared riparian ecotones and associated non-riparian upland fynbos. Fieldwork was performed in mountain and foothill sections of six perennial river systems within the south-western Cape. Eleven sites of three categories were chosen: four natural sites (uninvaded); four moderate to highly invaded sites (predominantly A. mearnsii); and three cleared sites (a formerly invaded site that had been cleared more than 7 years prior to the study). Within each site, four to five replicate plots were established along each of three geomorphological zones (wet bank, dry bank, and upland fynbos). Seasonal soil samples were collected for a period of one year. Results from this study showed that PFT cover and composition, soil physical and chemical properties and rates of nitrogen (N) and phosphorus (P) mineralization differed amongst invasion status, between geomorphological zones and across seasons. Regarding most soil physical and chemical properties and indices N and P cycling, river floodplains (dry banks) were very similar to terrestrial uplands. Acacia spp. changes soil properties and affects plant functional attributes by i) enriching the system with N; ii) enhancing litter inputs; iii) altering soil physical properties; iv) changing the composition and reducing the cover of PFT; and v) enhancing P mineralization rates. Although measured soil physical and chemical properties and N and P mineralization rates were reduced to levels that were similar to or resembled the situation at natural areas, available inorganic N remained two times higher after more than seven years of clearance. Furthermore, cleared areas were characterized by sparse woody cover and a high cover of alien grasses. Correlations between soil silt and clay content and several soil properties measured in this and other studies indicates important linkages between soil texture and resource availability. Clearing Acacia spp. may initiate restoration of invaded riparian ecosystems, but changes in ecosystem function (e.g. elevated soil N availability) as a result of invasion may necessitate active restoration following the removal of the alien species. Active restoration under such conditions would be required to facilitate the restoration of cleared riparian communities. However, we still lack the mechanistic understanding around fynbos riparian recovery after clearing, as the success of restoration may depend on complex interaction and feedback cycles between plants and their physical environment. A greater comprehensive understanding of fynbos riparian ecological processes will not only improve the effectiveness of restoration initiatives by integrating science and management, but also advance the field of riparian ecology.
AFRIKAANSE OPSOMMING: Rivier oewerwal-areas, oorgang gebiede tussen aangrensende terrestriële gemeenskappe en akwatiese ekosisteme, is baie dinamiese en komplekse ekosisteme met intrinsieke ekologiese eienskappe wat verskil in struktuur, funksie (bv. biogeochemie siklusse) en temporale dinamika. Oewerhabitatte langs riviere van die Mediterreense suid-wes Kaap is sensitief vir omgewingsveranderinge en kwesbaar vir indringing deur uitheemse plante (bekend as “invasive alien plants” (IAPs)), veral stikstof-fiksering Acacia spp., en relatief min werk het nog gefokus op hoe ekosisteme in die streek reageer op sulke veranderinge in die omgewing. Die belangrike rol wat gesonde oewerwal plantegroei speel in die handhawing van ekosisteemdienste- en integriteit, is al hoe meer uitgelig soos ons die agteruitgang van hierdie habitat in ag neem. Terwyl die Werk vir Water (WvW)-program al dat baie suksesvol was in die uitwissing van IAPs in oewersones in die kort termyn, is die mate waarin oewer-ekostelsels herstel na skoonmaakaksies swak verstaan. Fynbos oewerwal-areas is grootliks ingeneem deur houtagtige IAPs, veral stikstof fiksering Acacia spp. (soos Acacia mearnsii). Die resultate wat in hierdie studie aangebied is, het verskillende aspekte van oewer- struktuur en funksie aangespreek en dien as middel vir toekomstige navorsing en bestuur van oewerwal ekosisteme deur by te dra tot die evaluering van die sukses van skoonmaak inisiatiewe en die herstelproses daarvan. Die doel van hierdie projek was om die moontlikhede vir herstel van fynbos owerwal-ekostelsels te evalueer deur middel van verskeie grond- fisiese en chemiese eienskappe; plant funksionele groep dekking (genoem ‘plant functional types’ (PFT)); en geselekteerde grond biogeochemie prosesse in natuurlike, Acacia- aangetaste, en skoongemaakte rivierstelsels en nabygeleë terrestriese areas te vergelyk. Veldwerk is gedoen in bergstroom en voetheuwel rivierseksies van ses standhoudende rivierstelsels in Suid-wes Kaap, Suid Afrika. Van uit hierdie geselekteerde rivierstelsels is elf studie areas van drie kategorieë (of indringing status) gekies: vier natuurlike areas (nie aangetas); vier gematig- tot hoogs aangetaste areas (hoofsaaklik A. meanrsii); en drie skoongemaakte areas (rivieroewers wat meer as sewe jaar van te vore skoongemaak is). Binne elke studie area was vier tot vyf soortgelyke persele gevestig by elke van drie breë geomorfologiese sones: naamlik nat-, droë en hoogliggende terrestriese fynbos. Seisoenale grondmonsters vir 'n tydperk van een jaar is geneem. Resultate van hierdie studie het getoon dat PFT dekking en samestelling, grond fisiese- en chemiese eienskappe en N-mineralisasie en suur fosfatase aktiwiteit verskil tussen indringing status, geomorfologiese sones en oor seisoene. Ten opsigte van meeste grond fisiese en chemiese eienskappe en indekse van stikstof (N) en fosfor (P) siklusse kom die rivier vogregimes (droë oewersones) baie ooreen met die terrestriële gebiede. Aan die anderkant is die natbanksones gekenmerk deur grondeienskappe wat baie verskil van die ander twee geomorfologiese gebiede. Die gegewens ondersteun die hipotese dat indringing deur Acacia spp. verskeie grondeienskappe verander en plante se funksionele kenmerke beïnvloed deur i) die sisteem met voedingstowwe te verryk (veral N); ii) verhoog die toevoeging van plantmateriaal; iii) verander grond fisiese eienskappe; iv) verander die samestelling en verminder die dekking van PFT; v) en verhoog P biogeochemie. Hoewel grond fisiese -en chemiese eienskappe, en indekse van N en P mineralisasie verminder is tot vlakke wat soortgelyk aan natuurlike areas, het beskikbare anorganiese N twee keer hoër gebly by skoongemaakte gebiede. Nietemin, voorheen skoongemaakte gebiede is weer-binnegeval deur eksotiese grasse en die regenerasie of hertelling van inheemse fynbos gemeenskappe is taamlik beperk, veral houtagtige oewer struike en bome. Korrelasies tussen grond slik-en klei-inhoud en verskeie grondeienskappe gemeet in hierdie en ander studies dui op belangrike skakeling tussen die grondtekstuur en voedingstof beskikbaarheid. Die opruiming van Acacia spp. mag as aansporing dien vir die herstellingsproses van rivieroewerstelsels, maar veranderinge in die funksie van ekosisteme (bv. verhoogte grond N beskikbaarheid), as gevolg van indringing, mag aktiewe herstel noodsaak nadat die indringer spesies verwyder is. Aktiewe herstel onder sulke omstandighede sal verwag word om die herstel van skoongemaak oewer gemeenskappe te fasiliteer. Ons het wel egter nog 'n gebrek aan die meganistiese begrip in verband met die herstel van fynbos oewerwal areas na opruimings-inisiatiewe, sedert die sukses van herstel kan afhang van komplekse interaksie en terugvoer siklusse tussen die plante en hul fisiese omgewing. ʼn Meer omvattende begrip van fynbos rivieroewer ekologiese prosesse sal nie net die doeltreffendheid van opruimings-inisiatiewe deur die integrasie van wetenskaplike navorsing en bestuur verbeter nie, maar ook vooraf die gebied van rivieroewer-ekologie.
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Amichev, Beyhan Y. "Biogeochemistry of Carbon on Disturbed Forest Landscapes." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27328.
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Carbon accreditation of forest development projects is essential for sequestering atmospheric CO2 under the provisions of the Kyoto Protocol. The carbon sequestration potential of surface coal-mined lands is not well known. The purpose of this work was to determine how to measure carbon sequestration and estimate the additional amount that could be sequestered using different reforestation methods compared to the common practice of establishing grasslands.
I developed a thermal oxidation technique for differentiating sequestered soil carbon from inorganic and fossilized carbon found at high levels in mine soils along with a geospatial and statistical protocol for carbon monitoring and accounting. I used existing tree, litter, and soil carbon data for 14 mined and 8 adjacent, non-mined forests in the Midwestern and Eastern coal regions to determine, and model sequestered carbon across the spectrum of site index and stand age in pine, mixed, and hardwood forest stands. Finally, I developed the framework of a decision support system consisting of the first iteration of a dynamic model to predict carbon sequestration for a 60-year period for three forest types (white pine, hybrid poplar, and native hardwoods) at three levels of management intensity: low (weed control), medium (weed control and tillage) and high (weed control, tillage, and fertilization).
On average, the highest amount of ecosystem carbon on mined land was sequestered by pine stands (148 Mg ha-1), followed by hardwood (130 Mg ha-1) and mixed stands (118 Mg ha-1). Non-mined hardwood stands contained 210 Mg C ha-1, which was about 62% higher than the average of all mined stands. After 60 years, the net carbon in ecosystem components, wood products, and landfills ranged from 20 to 235 Mg ha-1 among all scenarios. The highest net amount of carbon was estimated under mixed hardwood vegetation established by the highest intensity treatment. Under this scenario, a surface-mined land of average site quality would sequester net carbon stock at 235 Mg C ha-1, at a rate of 3.9 Mg C ha-1 yr-1, which was 100% greater than a grassland scenario. Reforestation is a logical choice for mined land reclamation if carbon sequestration is a management objective.Ph. D.
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Bernier, Luc Warren Lesley A. "Sulphur biogeochemistry in a mine tailings lake." *McMaster only, 2007.
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Frei, Sven [Verfasser], and Jan H. [Akademischer Betreuer] Fleckenstein. "Interactions between hydrology and biogeochemistry within riparian wetlands : Riparian wetlands: hydrology meets biogeochemistry / Sven Frei. Betreuer: Jan H. Fleckenstein." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059353334/34.
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Shields, Amy Rebecca. "Biogeochemistry and phytoplankton dynamics in the Ross Sea, Antarctica." W&M ScholarWorks, 2007. http://web.vims.edu/library/Theses/Shields07.pdf.
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Müller-Niggemann, Cornelia [Verfasser]. "Lipid biogeochemistry of paddy soils / Cornelia Müller-Niggemann." Kiel : Universitätsbibliothek Kiel, 2016. http://d-nb.info/1082237086/34.
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Reynolds, Sarah. "The biogeochemistry of nitrogen in the Atlantic Ocean." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491105.
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Nitrogen plays a fundamental role in limiting the primary productivity of the world's oceans. The Atlantic Ocean is characterised by N-starved oligotrophic gyres to the north and south of the equator, which arise from wind induced Ekman flux of surface waters over the subtropics, subsequent downwelling and the production of a depressed, thicker thermocline. Discrepancies exist between the traditional supplies of N to and the export production from the surface waters of the oligotrophic gyres. This thesis focuses on the importance of N2 fixation and the potential role that organic nitrogen has on fuelling export production in the Atlantic Ocean by examining the biogeochemistry of organic nitrogen. The study formed part of the Atlantic Meridional Transect (AMT) programme and involved three northbound cruises between the Falkland Islands or Cape Town and the U.K., where organic nitrogen was sampled from the euphotic zone of the various biogeochemical regimes of the Atlantic. The spatial extent or' N2 fixation was assessed through the use of stable nitrogen isotope analysis of suspended pa.rticulate organic nitrogen (PONsusp). Consistently depleted signals (with respect to 15N) extend over the centre of the northern subtropical gyre; this partly coincides with a region where the tracer N* increases westward following the gyre circulation. The non-conservative behaviour of N* implies that N2fixation is responsible for the depleted 815N PONsusp• A mixing model suggests that N2 fixation over parts of the northern gyre provides up to 74% of the N utilised by phytoplankton. However, since the PONsusp represents only a small fraction of total N, N2 fixation probably plays a minor role in supplying new N to the photic zone of the northern subtropical gyre. The dynamics of organic nitrogen were investigated through the identification and quantification of dissolved free and hydrolysable, and particulate amino acids. Concentrations along AMT varied with biogeochemical regime; amino acids were depleted in the centres of both the northern and southern oligotrophic gyres and elevated in the higher productivity regions around the equator and temperate zones. The application of the Dauwe and Middleburg [1998] degradation index demonstrated that the 'age' of organic matter also varied, in that more degraded material was found in the gyres compared with the equator and temperate regions. These findings suggest that organic nitrogen can provide a source of N to primary producers. Examination of the enantiomeric ratios of chiral amino acids revealed that bacteria make a minor contribution to dissolved organic nitrogen in the open ocean, contradicting previous claims of bacterial contributions of 45-80%. Bacteria make a more substantial contribution of the particulate organic nitrogen. Surprisingly, archaea dominated the particulate pool, which is consistent studies revealing they are the dominant prokaryote in the world's oceans. Supplied by The British Library - 'The world's knowledge'
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Lannuzel, Delphine. "Iron biogeochemistry in the Antartic sea ice environment." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210775.
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Montross, Scott Norman. "Biogeochemistry of basal ice from Taylor Glacier, Antarctica." Diss., Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/montross/MontrossS0512.pdf.
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The thesis addresses a topical and exciting question in cryospheric biology: are microorganisms capable of metabolism in debris-rich basal ice of a polar glacier? The research was carried out on debris-rich basal ice from a cold-based glacier, Taylor Glacier, McMurdo Dry Valleys, Antarctica. A key component of the research was the collection and analysis of large parallel samples of basal ice for analysis of sediment concentration and mineralogy, nutrient and ion chemistry, gas composition, isotopic gas composition, cell density and metabolic activity on individual ~1-2cm thick layers. The primary material for the thesis was from a 4 m high section of basal ice collected from a vertical shaft at the end of a 15m tunnel chainsawed into the northern margin of the Taylor Glacier. Some data was derived from ice samples collected from tunnels 500m upglacier and downglacier from the 2007 tunnel, excavated in 1999 and 2009 respectively. The main research findings presented in this dissertation are that (a) debris-rich basal ice is a viable habitat for microbial life, (b) in situ microbial heterotrophic respiration is a source of CO ₂ in debris-rich basal ice, and (c) microbially-mediated weathering of entrained mineral debris is a source of solute in the ice. Geologic debris in basal ice is the key component for microbial activity since it leads to a higher fraction of liquid water in the ice and provides both organic and inorganic substrates to organisms in the ice. Microbial activity in the ice produces isotopic and geochemical signatures that could be used as biomarkers for exploration of other icy systems. The results of the thesis enforce the notion that the debris-rich basal ice environment is a viable microbial habitat that supports life at temperatures below 0°C. This has broader implications at the ice sheet scale since recent discoveries in East Antarctica, indicate significant basal ice up to 1100 m thick with approximately the same volume as the world's fourth largest freshwater lake, Lake Michigan-Huron. 'Co-authored by Mark Skidmore, Brent C. Christner, Denis Samyn, Jean Louis Tison, Reginald Lorrain, Shawn Doyle, Sean Fitzsimons, and Todd Sowers.'
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Wuttig, Kathrin [Verfasser]. "Manganese biogeochemistry in the sunlit ocean / Kathrin Wuttig." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1036242684/34.
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Mann, Paul J. "Ammonium Photoproduction and CDOM Biogeochemistry in Marine Systems." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525090.
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Percival, Philip. "Impacts of trawl fisheries on marine benthic biogeochemistry." Thesis, University of Newcastle Upon Tyne, 2004. http://hdl.handle.net/10443/708.
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Fishing is widely recognised as the largest anthropogenic impact on coastal marine ecosystems. Bottom trawling is both widespread and a major impacting activity with documented effects on target species, populations of non-target species, food web dynamics and habitat features. In this thesis the effects of trawling on the benthic biogeochemistry of the central west North Sea were investigated. Two areas with similar sediment properties were identified for comparative analysis of North Sea sediments from trawled and untrawled areas. A combination of field and complimentary microcosm experiments were employed to examine the impacts of commercial trawling on the assemblage of benthic macrofauna, distributions of dissolved nutrients and chromophoric dissolved organic matter (CIDOM). The infauna in trawled areas consisted of species, the size of which were on average -36 % smaller than those from untrawled areas, whereas total mean macrofaunal abundance was -60 % greater in trawled sediments. These size and abundance differences had a profound affect on bioturbation. Natural densities of bioturbators from untrawled sediments increased benthic fluxes relative to an abiotic situation by up to 81 % NH4+i 197 % P04 3-, 96 % N02- and 33 % N03-. Fauna from trawled sediments gave flux values that lay between untrawled faunal fluxes and fluxes from controls without fauna. In addition to the long-term alteration in sediment biogeochemistry resulting from altered faunistic composition the direct impact of trawl gear produced an enhanced sediment efflux for NH4+ (475 % greater than the background flux) and N02- (26 % greater than the background flux). In contrast, P04 3- influx, observed in systems without trawl impacts changed to a net efflux following trawl disturbance (-15 %). In contrast, N03-, displayed a net efflux in the control systems, yet, a decrease of -1.0 % was apparent following heavy trawling. Altered flux rates persisted for > 48 hours. During the main fishing season nutrient profiles were perturbed down to -4 cm in sediments from trawled sites. Nutrient concentrations in the top 4 cm of trawled sediments were characterised by a relatively homogenous surface sediment layer in which concentrations were significantly lower than concentrations in untrawled sediments. This thesis has demonstrated that the impacts of commercial trawl fisheries on benthic biogeochemistry in the North Sea are of a significant magnitude and scale to affect local and potentially regional nutrient dynamics.
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Edgar, Petrena Joyce. "Biogeochemistry of polychlorinated biphenyls (PCBs) in estuarine sediments." Thesis, University of the West of Scotland, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343348.
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Kang, Hojeong. "The significance of enzyme activities in wetland biogeochemistry." Thesis, Cardiff University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266828.
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Saito, Mak A. "The biogeochemistry of cobalt in the Sargasso Sea." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/58543.
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Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2001.Includes bibliographical references.
Processes that enable marine phytoplankton to acquire trace metals are fundamental to our understanding of primary productivity and global carbon cycling. This thesis explored the biogeochemistry of cobalt using analytical chemistry and physiological experiments with the dominant phytoplankton species, Prochlorococcus. A high sensitivity method for Co speciation was developed using hanging mercury drop cathodic stripping voltammetry. Dissolved Co at the Bermuda Atlantic Time Series station (BATS) in the Sargasso Sea was bound by strong organic complexes with a conditional stability constant of logK=16.3+0.9. A depth profile of Co at BATS revealed a nutrient-like profile. Biweekly time series measurements of total cobalt near Bermuda from the MITESS sampler were 0-47pM throughout 1999, and averaged 20±1 OpM in 1999. A transect of total cobalt from BATS to American coastal waters ranged from 19- 133pM and correlated negatively with salinity (r2=0.93), suggestive of coastal waters as an input source. Prochlorococcus strains MED4-Ax and SS120 showed an absolute requirement for Co, despite replete Zn. 57Co uptake rates and growth rates were enhanced by additions of filtered low Co cultures, suggesting that a ligand is present that facilitates Co uptake. Bottle incubations from a Synechococcus bloom in the Pacific showed production of 425pM strong cobalt ligand. These and other lines of evidence support the hypothesis that a cobalt ligand, or cobalophore, is involved in cobalt uptake. Co-limited Prochlorococcus cultures exhibited an increase in the fraction of cells in G2 relative to other cell cycle stages during exponential growth, and the durations of this stage increased with decreasing cobalt concentrations. This effect was not observed with Fe, N, or P-limited cultures, suggestive of a specific biochemical function of cobalt that would interfere with the late stages of the cell cycle. The ligand Teta was explored as a means to induce cobalt limitation. The CoTeta complex was not bioavailable to the Sargasso Sea microbial assemblage in short-term experiments. Bottle incubations with Teta did not induce cobalt limitation of Prochlorococcus. These results are consistent with the lower conditional stability constant for CoTeta (logK= 11.2+0.1) relative to natural cobalt ligands in seawater, and with culture studies that suggest uptake of cobalt via strong organic ligands.
by Mak A. Saito.
Ph.D.
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Waldbauer, Jacob Richard. "Molecular Biogeochemistry of modern and ancient marine microbes." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57991.
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Thesis (Ph.D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010.Cataloged from PDF version of thesis.
Includes bibliographical references.
Biological activity has shaped the surface of the earth in numerous ways, but life's most pervasive and persistent global impact has been the secular oxidation of the surface environment. Through primary production - the biochemical reduction of carbon dioxide to synthesize biomass - large amounts of oxidants such as molecular oxygen, sulfate and ferric iron have accumulated in the ocean, atmosphere and crust, fundamentally altering the chemical environment of the earth's surface. This thesis addresses aspects of the role of marine microorganisms in driving this process. In the first section of the thesis, biomarkers (hydrocarbon molecular fossils) are used to investigate the early history of microbial diversity and biogeochemistry. Molecular fossils from the Transvaal Supergroup, South Africa, document the presence in the oceans of a diverse microbiota, including eukaryotes, as well as oxygenic photosynthesis and aerobic biochemistry, by ca. 2.7Ga. Experimental study of the oxygen requirements of steroid biosynthesis suggests that sterane biomarkers in late Archean rocks are consistent with the persistence of microaerobic surface ocean environments long before the initial oxygenation of the atmosphere. In the second part, using Prochlorococcus (a marine cyanobacterium that is the most abundant primary producer on earth today) as a model system, we explored how microbes use the limited nutrient resources available in the marine environment to make the protein catalysts that enable primary production. Quantification of the Prochlorococcus proteome over the diel cell-division cycle reveals that protein abundances are distinct from transcript-level dynamics, and that small temporal shifts in enzyme levels can redirect metabolic fluxes. This thesis illustrates how molecular techniques can contribute to a systems-level understanding of biogeochemical processes, which will aid in reconstructing the past of, and predicting future change in, earth surface environment
by Jacob Richard Waldbauer.
Ph.D.
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Fitzsimmons, Jessica Nicole. "The marine biogeochemistry of dissolved and colloidal iron." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84914.
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Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Iron is a redox active trace metal micronutrient essential for primary production and nitrogen acquisition in the open ocean. Dissolved iron (dFe) has extremely low concentrations in marine waters that can drive phytoplankton to Fe limitation, effectively linking the Fe and carbon cycles. Understanding the marine biogeochemical cycling and composition of dFe was the focus of this thesis, with an emphasis on the role of the size partitioning of dFe (<0.2 jm) into soluble (sFe<0.02 jm) and colloidal (0.02ptm
by Jessica Nicole Fitzsimmons.
Ph.D.
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Rusiecka, Dagmara. "Biogeochemistry of trace metals in European shelf seas." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/425510/.
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Shelf seas are considered an important source of trace metals (TMs) to the open ocean. However, the processes controlling distributions of dissolved TMs (DTMs) in shelf seas, their seasonal variability and the mechanisms facilitating off-‐shelf transport to the open ocean are not well constrained. Reported here is the first seasonal study of the DTMs, cadmium (DCd), zinc (DZn), nickel (DNi) copper (DCu) manganese (DMn), cobalt (DCo), aluminium (DAl) and lead (DPb) and their contrasting biogeochemical behaviours in the Celtic Sea continental system. Strong correlations (r2 = 0.91 – 0.97, n = 454) between nutrient-‐like metals (DCd, DZn, DCu, DNi, DCo (surface waters only)) and macronutrients (phosphate (PO43-‐) and silicic acid (SiO44-‐) were observed over all seasons (autumn, spring and summer) indicating that biological uptake in the euphotic zone and remineralization of sinking phytoplankton debris in deeper waters form key controls on their distributions. The correlation between DAl and PO43-‐ (r2 = 0.80) and SiO44-‐ (r2 = 0.85) in the upper waters (< 1500 m depth) mimicked the DZn distributions, which was a surprising observation and requires further investigation. Variable DTM ratios relative to PO43-‐ were observed across different seasons in off-‐shelf surface waters and for DCd and DZn (full depth profiles) across the continental shelf. Observations from the Celtic Sea region suggest the influence of distinct water masses, phytoplankton community structure and potentially metal specific biogeochemical processes, on DTMs distributions on a seasonal time-‐scale. Dissolved Co and Mn were more strongly influenced by scavenging and sedimentary inputs. Vertical distributions of DMn showed a typical scavenged type behaviour with enhanced surface waters concentrations from atmospheric inputs combined with photochemical stabilisation. Enhanced DMn and DCo concentrations were observed close to slope sediments and extended away from the shelf at intermediate depths. These observations were related to suspended sediments as indicated by increased signals in turbidity and short-‐lived 223Ra and 224Ra isotopes (tracers of sediment inputs). This implies that resuspended shelf or slope sediments can act as a source of DMn and DCo that can be transported to the adjacent open ocean. The full depth relationship of DCo with PO43-‐ revealed a shift in dominant biogeochemical processes controlling DCo vertical distributions in the study region. While biological uptake and remineralization were dominant processes in surface waters, as indicated by a strong correlation with PO43-‐ (r = 0.89), a gradual decoupling of DCo from PO43-‐ at intermediate depths was suggestive of progressive scavenging and less pronounced remineralization and a significant negative correlation (r = -‐0.72) in deeper waters (> 1500 m depth) was suggestive of scavenging as the dominant process at these depths. Beside the natural sources of DTMs, anthropogenic activities have resulted in enhanced DTMs emissions to the environment over the past centuries. Lead has a strong anthropogenic signal as a result of the combustion of leaded fuel and coal. Presented here is the first combined DPb, labile Pb (LpPb) and particulate Pb (PPb) distributions from the Celtic Sea since the phasing out of leaded fuel in Europe. Concentrations of DPb in surface waters have decreased by 4-‐fold over the last four decades. Nevertheless, a distinct anthropogenic Pb signal was observed from the Mediterranean Sea at intermediate depths, showing that Pb can transported over long distances (>2500 km). Benthic DPb fluxes exceeded the atmospheric Pb fluxes in the region, indicating the importance of sediments as a contemporary Pb source. A strong positive correlation between DPb, PPb and LpPb indicates a dynamic equilibrium between the phases and the potential for particles to ‘buffer’ the DPb pool. This study highlights the requirements of continuing efforts in regulating Pb emissions but also of detailed seasonal TMs studies in coastal systems in future. Results reported here provide insights into distinct biogeochemical processes in oceanographically dynamic shelf seas and demonstrates the potential of Pb in constraining ocean circulation patterns.
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Cole, Catherine. "Biogeochemistry of hydrothermal systems in the Scotia Sea." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/363754/.
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Submarine hot springs play an important role in global heat transfer; element cycling; economic ore deposition; and as an energy source for chemosynthetic ecosystems. Almost four decades of deep-sea exploration have revealed hydrothermal venting to be a ubiquitous phenomenon across the global ocean floor, yet these systems have only recently been discovered in Antarctica. Between 1998 and 2012, high-temperature vents were detected and sampled along the East Scotia Ridge (ESR) and within the Kemp Caldera, which forms part of the South Sandwich island arc, during four research cruises to the Scotia Sea. These vent sites are the first discovered south of the polar front, and they have a distinct faunal assemblage that has characterised them as a new biogeographic province. In this thesis, I investigate the controls on hydrothermal fluid chemistry at the ESR and the Kemp Caldera, using the rare earth elements (REEs) as geochemical tracers. I demonstrate that REE distributions in hydrothermal fluids and associated sulphate deposits are variably influenced by reaction with the host rock; temperature and phase separation; fluid composition and magmatic gas injection; and anhydrite precipitation/dissolution. Secondly, I assess tissue bioaccumulation of metals in Kiwa tyleri sp. nov., the dominant macrofaunal species at the ESR vent sites, in response to their environmental exposure. Significant variation in metal burden between tissues reflects both abiotic and biotic controls on metal uptake, including external concentration; trophic position; ecological niche and behavioural traits; in addition to cellular mechanisms of regulation. Finally, I investigate proteomic pathways of metal regulation in the shallow water mussel, Mytilus edulis, and the vent-living mussel, Bathymodiolus sp. I show that both species have strong defence mechanisms against metal toxicity and oxidative stress, which may be important for successful colonisation of hydrothermal systems. This work highlights the diversity in chemical compositions of fluids venting in back-arc and island-arc settings, and provides an insight into metal regulatory mechanisms that may have facilitated faunal colonisation of these extreme habitats.
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Sadurski, Stephen Edward. "The Biogeochemistry of Carbon Isotopes in Local Lakes." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1357745315.
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Rebecca, 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.
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Marois, Darryl Evan. "Modeling Wetland Biogeochemistry and Restoration in South Florida." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437578127.
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Pohlman, John W. "Sediment biogeochemistry of northern Cascadia margin shallow gas hydrate systems." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539616813.
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Methane contained in gas hydrate is a significant component of the global organic carbon inventory. Describing the methane sources supporting these systems and the mechanisms that control the distribution of methane in marine sediments are critical elements in evaluating the resource potential, climate change implications and geologic hazards associated with gas hydrate. The northern Cascadia margin (offshore Vancouver Island, Canada) is a convergent margin with gas hydrate-bearing cold seeps composed of both thermogenic (Barkley Canyon) and microbial (Bullseye vent) gas sources. Gas hydrate and sediment cores were collected from each of these settings to examine the sources that sustain the gas hydrate and the biogeochemical processes that control the flux and cycling of methane carbon within the cold seep system. Gas hydrate bound methane from Barkley Canyon, Bullseye vent and four other oceanic locations was primarily synthesized from "fossil" organic matter devoid of radiocarbon. Recognizing that the global gas hydrate reservoir is comprised of fossil carbon may alter our understanding of how gas hydrate methane influences the radiocarbon content of other ocean carbon pools (e.g., dissolved organic carbon). Analysis of gas and oil samples from the thermogenic gas hydrate site, Barkley Canyon, indicated the thermogenic hydrocarbons were generated from a source rock with a low hydrocarbon producing potential. The pore water and sediment geochemistry from Barkley Canyon and Bullseye vent were evaluated to identify fluid flux regimes and the metabolic pathways that control how methane carbon was cycled by the microbial consortium. Evidence for coupling between anaerobic oxidation of methane (AOM) and methanogenesis was inferred from the stable carbon isotope composition of the dissolved inorganic carbon (DIC) and methane at both locations. Lipid biomarker analysis further indicated sulfate reducing bacteria consumed organic matter sources in addition to methane. This study demonstrated the value of integrating geochemical, chronological and geophysical data to understand the sources and cycling of methane in cold seep systems and provided a more comprehensive model for how the northern Cascadia margin is interconnected and how the gas hydrate system has evolved.
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Wellington, Brian Ishmael. "Controls on dissolved organic carbon at Hubbard Brook Experimental Forest and its effects on stream acid-base chemistry." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2002. http://wwwlib.umi.com/cr/syr/main.
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Thibault, Pierre-Jean. "Caractérisation de la ferrihydrite authigénique synthétisée sous différentes conditions et en présence ou absence de bactéries." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6116.
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2-ligne ferrihydrite was synthesized under different conditions, then characterized by transmission electron microscopy, by X-ray diffraction and particularly by Mossbauer spectroscopy. Three synthesis media have been investigated: (1) in the presence of Bacillus subtilis bacteria, (2) in the presence of Bacillus licheniformis and (3) abiotic, at different concentrations of iron (1 x 10-3 M, 5 x 10-3 M and 1 x 10-4 M) and different pH, (6, 7, 8 and 9). We have also studied the effects: of two precursor salts in the synthesis (FeCl2·4H 2O and FeNO3·9H2O), of the drying method (wet, air-dried or freeze-dried) and of the aging of the samples. We have found that the presence of bacteria affects the crystallinity and creates structural disorder. At lower iron concentration, the biotic samples show some Fe2+. The concentration and aging variations show opposite trends between biotic and abiotic samples. The type of salt used has an important effect but the pH and the drying method have a much smaller one. The thesis comprises a literature review of the Mossbauer parameters of ferrihydrite.
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El, Bilali Larbi. "Role of biogeochemical processes in metal cycling in remote lakes from the Huntsville and Clyde Forks areas, Ontario, and Kejimkujik Park, Nova Scotia, Canada." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9071.
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The study of metal speciation and the role of biogeochemical processes in metal distribution and cycling in lake sediments was carried out in remote lakes from the Huntsville and the Clyde Forks areas, Ontario and Kejimkujik Park, Nova Scotia, Canada. Based on geochemical data and sequential extraction results of trace elements from sediment cores of 20 lakes from the Huntsville region, Ontario, Canada, it was demonstrated that relative affinities to organic matter and mineral fractions (silicates) played an important role in the distribution of total metal values and hence in the shape of the metal concentration profiles. The importance of atmospheric and geological trace metal fluxes was studied by using sediment traps in two circum-neutral remote lakes, Lavant Long Lake and Perch Lake, in Lanark County, southeastern Ontario, Canada, to measure sedimentation rates, to quantify trace element fluxes from watershed and atmospheric sources, and to investigate the distribution of elements amongst component phases of the trapped sediments. The results of this study showed that local watershed sources were the dominant source of Hg, Cu, Al, Fe, Mn, Sb, in both lakes with ratio sometimes exceeding 9:1 (geogenic to atmospheric). The study of the effect of humic substances (HS) content and their transformation on their interaction with metals was carried out in three remote lakes: Lavant Long Lake, Perch Lake; and Big Dam Lake. HS transformation was demonstrated by the increase of HA aromaticity and the decrease of the E4/E6 ratio in Lavant Long Lake, by the increase of 13C resonance signal in the aromatic-C region (105--150 ppm) in Perch Lake, and by the gradual decrease of the HS content with depth in Big Dam Lake. A quantitative study of trace metal cycling between pore waters and sediments using the most comprehensive diagenetic models was carried out using a two-layer diagenesis model to account for the bioturbation zone and the zone below the bioturbation zone. Sulfate reducing bacteria (SRB) populations were determined in the three lakes using the most probable number (MPN) method. In the zone of bioturbation of Perch Lake, Co, Cu, and Hg predicted and observed concentrations in the pore waters were close. In Lavant Long Lake and for the rest of the elements in Perch Lake, trace metal concentrations predicted by the model were generally lower than the observed. (Abstract shortened by UMI.)
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Brown, Ann. "Methane production in Canadian muskeg bogs." Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/21229.
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Stanley, Nicolette. "Effect of various biogeochemical processes on mercury methylation in copper-zinc and gold mine tailings." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27043.
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Mercury is a well known environmental pollutant. Anthropogenic sources include coal combustion, waste incineration and metal processing. In base metal mines, Hg is often left in the mining wastes (i.e., mine tailings). Once disposed of in open-air impoundments, these Hg-containing tailings can undergo various biogeochemical transformations, including Hg methylation. It is the methylated form of mercury (MeHg) that poses a threat to the environment, because it bio-accumulates at each level of the food chain. The present study was undertaken to assess the biogeochemical factors affecting Hg methylation in Cu-Zn and Au mine tailings. The study focused on the role of sulfate-reducing bacteria (SRB) because they are suspected to be associated with Hg methylation. Temperature, sulfate and organic carbon availability, along with SRB activity were tested as potential factors affecting Hg methylation in column experiments containing old Au tailings and fresh Cu-Zn tailings. The results first showed that SRB activity did not enhance Hg methylation in Cu-Zn tailings and Au tailings, indicating that iron reducing bacteria, and not SRB, along with abiotic methylation reactions played an important role. Cold temperatures did not slow down SRB activity and MeHg production, but the accidental freezing and thawing of the Cu-Zn tailings promoted the production of soluble MeHg. The mechanism responsible for this unexpected Hg methylation is however unknown. Elevated organic carbon and sulfate concentrations did enhance SRB activity, but not MeHg formation in the tailings, because increased sulfide production hindered Hg methylation. Tailings mineralogy played a significant role in the production of methyl mercury, Au tailings contained more soluble and solid-bound MeHg than Cu-Zn tailings. These results add to the increasing amount of information on Hg cycling in the environment, and indicate that SRB might not be the dominant Hg methylators in mining environments.
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Lis, Grzegorz P. "Effects of thermal maturation on organic hydrogen-2/hydrogen-1 ratios and hydrogen isotopic exchangeability in Paleozoic marine kerogens (type-II)." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3223056.
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Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2006."Title from dissertation home page (viewed June 28, 2007)." Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 3014. Advisers: Arndt Schimmelmann; Maria Mastalerz.