Segui questo link per vedere altri tipi di pubblicazioni sul tema: Carbon cycle (Biogeochemistry).
Tesi sul tema "Carbon cycle (Biogeochemistry)"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Carbon cycle (Biogeochemistry)".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Cordova, Vicente D. "Regional-scale carbon flux estimation using MODIS imagery". Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1325989.
Testo completoAbstract (sommario):
The National Aeronautics and Space Agency NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) platform carried by Terra and Aqua satellites, is providing systematic measurements summarized in high quality, consistent and well-calibrated satellite images and datasets ranging from reflectance in the visible and near infrared bands to estimates of leaf area index, vegetation indices and biome productivity. The objective of this research was to relate the spectral responses and derived MODIS products of ecosystems, to biogeochemical processes and trends in their physiological variables. When different sources of data were compared, discrepancies between the MODIS variables and the corresponding ground measurements were evident. Uncertainties in the input variables of MODIS products algorithms, effects of cloud cover at the studied pixel, estimation algorithm, and local variation in land cover type are considered as the cause. A simple "continuous field" model based on a physiologically-driven spectral index using two ocean-color bands of MODIS satellite sensor showed great potential to track seasonally changing photosynthetic light use efficiency and stress-induced reduction in net primary productivity of terrestrial vegetation. The model explained 88% of the variability in Flux tower-based daily Net Primary Productivity. Also a high correlation between midday gross CO2 exchange with both daily and 8-day mean gross CO2 exchange, consistent across all the studied vegetation types, was found. Although it may not be possible to estimate 8-day mean Light Use Efficiency reliably from satellite data, Light Use Efficiency models may still be useful for estimation of midday values of gross CO2 exchange which could then be related to longer term means of CO2 exchange. In addition, the MODIS enhanced vegetation index shows a high potential for estimation of ecosystem gross primary production, using respiration values from MODIS surface temperature, providing truly per-pixel estimates.Department of Natural Resources and Environmental Management
2
Halloran, Paul R. "Rapid changes in the global carbon cycle". Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:cfb93401-3313-4948-a74b-e7e44a068f15.
Testo completoAbstract (sommario):
The flux of carbon in to and out of the atmosphere exerts a fundamental control over the Earth's climate. The oceans contain almost two orders of magnitude more carbon than the atmosphere, and consequently, small fluctuations within the oceanic carbon reservoir can have very significant effects on air-sea CO2 exchange, and the climate of the planet. Pelagic carbonates represent a major long-term flux of carbon from the surface ocean to deep-sea sediments. Within sediments, the biologically produced carbonates act as a longterm carbon store, but also as chemical recorders of past surface ocean conditions. Counterintuitively, despite the production and sedimentation of carbonate acting as a CO2 sink, over periods shorter than the mixing-time of the ocean, the pH change associated with calcium carbonate precipitation enriches the surface waters in CO2 and elevates the equilibrium value of gaseous exchange with the atmosphere. Coccolithophores, ubiquitous marine photosynthetic plankton, produce calcium carbonate plates, coccoliths, which account for around one third of all marine calcium carbonate production. Sedimentary coccoliths therefore represent a valuable repository of surface ocean geochemical data, as well as a very significant carbon-cycle flux. This thesis examines how the mass of calcium carbonate produced by coccolithophores has changed in response to rising levels of atmospheric CO2. A -40% increase in average coccolith mass over the last 230 years, paralleling anthropogenic CO2 release, is demonstrated within a high-accumulation rate North Atlantic sediment core. Additionally, a flow-cytometry method is presented, which enables the automatic separation of coccoliths from clay particles in sedimentary samples, representing the first step in a coccolith cleaning procedure, which should ultimately enable down-core measurements of coccolith trace-element/calcium ratios. Complementing this work I describe results from continuous dissolution analysis of cultured coccoliths which allows a first-order evaluation of trace-element partitioning into coccoliths produced by the species Coccoliths pelagicus, and present a conceptual methodology to allow the determination of single-species coccolith chemical data.
3
Holmes, Brett. "Mobilization of Metals and Phosphorous from Intact Forest Soil Cores by Dissolved Inorganic Carbon: A Laboratory Column Study". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/HolmesB2007.pdf.
Testo completo
4
Trudinger, Catherine Mary. "The carbon cycle over the last 1000 years inferred from inversion of ice core data /". Full text, 2000. http://www.dar.csiro.au/publications/Trudinger_2001a0.htm.
Testo completo
5
Ridgwell, Andy J. "Glacial-interglacial perturbations in the global carbon cycle". Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365134.
Testo completo
6
Kambis, 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.
Testo completoAbstract (sommario):
A numerical model of the global carbon cycle is presented which includes the effects of anthropogenic &CO\sb2& emissions &(CO\sb2& produced from fossil fuel combustion, biomass burning, and deforestation) on the global carbon cycle. The model is validated against measured atmospheric &CO\sb2& concentrations. Future levels of atmospheric &CO\sb2& are then predicted for the following scenarios: (1) Business as Usual (BaU) for the period 1990-2000; (2) Same as (1), but with no biomass burning; (3) Same as (1), but with no fossil fuel combustion; (4) Same as (1), but with a doubled atmospheric &CO\sb2& concentration and a 2 K warmer surface temperature associated with the doubled atmospheric &CO\sb2& concentration. The global model presented here consists of four different modules which are fully coupled with respect to &CO\sb2.& These modules represent carbon cycling by the terrestrial biosphere and the ocean, anthropogenic &CO\sb2& emissions, and atmospheric transport of &CO\sb2.&. The prognostic variable of interest is the atmospheric &CO\sb2& concentration field. The &CO\sb2& concentration field depends on both the sources and sinks of &CO\sb2& as well as the atmospheric circulation. In addition, the sources and sinks vary significantly as a function of both time and geographic location. The model output agrees well with measured data at the equatorial and mid latitudes, but this agreement weakens at higher latitudes. This is due to the less adequate representation of the terrestrial ecosystem models at these latitudes. In the first scenario, the predicted concentration of atmospheric &CO\sb2& is 362 parts per million by volume (ppmv) at the end of the 10 year model run. This establishes a baseline for the next three scenarios, which predict that biomass burning will contribute 3 ppmv of &CO\sb2& to the atmosphere by the year 2000, while fossil fuel combustion will contribute 5 ppmv. The net effect of a 2 K average global warming was to increase the atmospheric &CO\sb2& concentration by approximately 1 ppmv, due to enhanced respiration by the terrestrial biosphere.
7
Carozza, David. "Carbon cycle box modeling studies of the Paleocene-Eocene thermal maximum". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66818.
Testo completoAbstract (sommario):
Approximately 55 million years ago, an unprecedented amount of light carbon was abruptly released into the ocean and atmosphere. This event, known as the Paleocene-Eocene thermal maximum (PETM), is documented by large negative carbon isotope excursions in marine and soil carbonates and by global environmental changes. Models have been applied to constrain the amount of carbon released during the PETM. In this study, the Walker-Kasting carbon cycle box model is revisited and, after correcting its carbon isotope equations, it is used to resolve a discrepancy in previous emission estimates. In addition, the atmospheric methane box model of Schmidt-Shindell is coupled to the Walker-Kasting model to explore the role of methane during the PETM. This coupled model is then combined with results from other modeling studies to demonstrate that the PETM may have been caused by the rel ease of approximately 3500 Pg C of thermogenic methane into the Atlantic Ocean.Il y a environ 55 millions d'années, une quantité sans précédent de carbone a été brusquement libérée dans l'océan et l'atmosphère. Cet événement, désigné de maximum thermique Paléocène-Eocène (PETM), est identifiable par de remarquables excursions négatives de del13C en carbonate marin et sol, et par des bouleversements environnementaux d'échelle globale. Plusieurs modèles ont été utilisés afin d'estimer la quantité de carbone émise durant le PETM. Cette étude reprend le modèle du cycle du carbone de Walker-Kasting, révise ses équations du del13C et l'utilise pour résoudre un désaccord entre des estimés antérieures de l'émission totale. Le modèle du méthane atmosphérique de Schmidt-Shindell est également couplé à celui de Walker-Kasting dans le but d'examiner l'importance du méthane durant le PETM. Finalement, ce modèle couplé, en combinaison avec les résultats d'autres modèles, est implémenté pour démontrer que le PETM aurait pu être engendré par l'émission de 3500 Pg C de méthane thermogénétique à l'océan Atlantique.
8
Smith, Joanne Caroline. "Particulate organic carbon mobilisation and export from temperate forested uplands". Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648250.
Testo completo
9
Ferretti, Dominic Francesco. "The development and application of a new high precision GC-IRMS technique for N₂O-free isotopic analysis of astmospheric CO₂". [Wellington, New Zealand] : Victoria University of Wellington, 1999. http://catalog.hathitrust.org/api/volumes/oclc/154329143.html.
Testo completo
10
Bachman, Sarah. "Elevated atmospheric carbon dioxide and precipitation alter ecosystem carbon fluxes over northern mixed-grass prairie at the prairie heating and CO2 enrichment (PHACE) experiment in Cheyenne, Wyoming, USA". Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1445355711&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Testo completo
11
Wang, 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.
Testo completoAbstract (sommario):
In this thesis, the "green" McGill Paleoclimate Model (MPM) is developed by interactively coupling the five-component physical MPM with a Dynamic Global Vegetation Model (DGVM) known as VECODE (VEgetation COntinuous DEscription model). Three applications to the pre-industrial Holocene climate, ocean, vegetation and terrestrial carbon cycle dynamics are presented, after a new land surface scheme is introduced. In these applications, orbital (Milankovitch) forcing and prescribed atmospheric CO2, starting from eight thousand years before present (8 kyr BP), are applied. In addition, a prescribed retreat of the Laurentide Ice Sheet (LIS) from 8 to 6 kyr BP is introduced. [Note: All acronyms used in this thesis are given in Appendix A.]The 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).
12
Blodau, 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.
Testo completoAbstract (sommario):
Nitrogen and sulfur deposition and water table level fluctuations have the potential to influence the C biogeochemistry in peatlands. Processes in peatland mesocosms were examined under steady state and dynamic conditions at different rates of N and S deposition, and water table levels. Net turnover rates were calculated from diffusive-advective mass-balances of pore water constituents. The limitations of the approach were tested with tracer experiments, which showed that diffusive-advective transport adequately described the flow of dissolved substances in peat columns. Incubation experiments quantified potential CO2, CH4, DOC, H2S and Fe 2+ production rates.The 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.
13
Roehm, Charlotte L. "Carbon dynamics in northern peatlands, Canada". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19545.
Testo completoAbstract (sommario):
Biogeochemical carbon dynamics govern the ability of peatlands to storecarbon. The processes controlling the balance between the photosyntheticuptake of C02 and respiration of C02 and CH4 back to the atmosphere remainunclear. A process-based ecosystem biogeochemical study, encompassing tracegas flux measurements, laboratory chemical analyses and field analyses, wasundertaken in order to better understand the carbon dynamics of borealCanadian peatlands.
14
Lee, Kern Y. "Carbon Cycling in Tropical Rivers: A Carbon Isotope Reconnaissance Study of the Langat and Kelantan Basins". Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30429.
Testo completoAbstract (sommario):
Despite the importance of tropical rivers to the global carbon cycle, the nature of carbon cycling within these watersheds has been dealt with by only a handful of studies. The current work attempts to address this lack of information, using stable isotope and concentration measurements to constrain sources and sinks of carbon in two Peninsular Malaysian watersheds. The basins are located on the central-western and northeastern coasts of the Malaysian Peninsula, and are drained by the Langat and Kelantan Rivers, respectively. Water samples were collected from three points along the two rivers twice a month, in addition to the sampling of groundwater in adjacent aquifers.
Principal component analyses (PCA) on water chemistry parameters in the Langat and Kelantan Rivers show the dominance of geogenic and anthropogenic influences, grouped in 4 to 6 components that comprise over 50 % of the total dataset variances. The geogenic input is reflected by components showing strong loadings by Ca, Mg, Mn, Si, and Sr, while anthropogenic influences via pollution are indicated via strong loadings by NO3, SO4, K, Zn and Cl. The carbon isotope and concentration data appear unrelated to these groups, suggesting that the riverine carbon cycle in both locations is dominated by other factors. These may include alternative sources of organic pollution, or inputs from the local vegetation and soils.
The mean riverine 13CDOC of -27.8 ± 2.9 ‰ and -26.6 ± 2.2 ‰ in the Langat and Kelantan Basins, respectively, are consistent with the dominance of C3-type vegetation in both watersheds. Riverine 13CDIC signatures approach C3-like values at high DIC concentrations, with measurements as low as -19 ‰ in the Kelantan Basin and -20 ‰ observed in the Langat Basin, consistent with a biological origin for riverine DIC. However, the average 13CDIC in river water is 13C-enriched by about 10 ‰ relative to the expected C3 source in both rivers, and this 13C- enrichment appears to be largest with smaller DIC concentrations.
Because of the overpressures of CO2 in the rivers, entrainment of isotopically-heavy atmospheric CO2 is not a likely explanation for the observed 13C-enrichment. Theoretically, dissolution of carbonates could be an alternative source of 13C-enriched carbon, but this lithology is scarce, particularly in the Langat watershed. The increase in DIC downstream and generally high pCO2 values in most river sections argues against aquatic photosynthesis as a primary causative factor for the observed isotopic enrichment. This elimination process leaves the speciation of riverine DIC and the evasion of CO2 as the most likely mechanisms for 13C-enrichment in DIC, via isotope fractionation during HCO3- hydration and CO2 diffusion. Potentially, methanogenic activity could also be, at least partially, responsible for the 13C-enrichment in DIC, particularly immediately downstream of the Langat Reservoir, but due to the absence of empirical data, this must remain only a theoretical proposition.
The aquatic chemistry and dissolved carbon data suggests that pollution discharge into the Langat and Kelantan Rivers is the major factor that is responsible for the considerable CO2 overpressures and high DIC and DOC concentrations in the river waters, particularly in the downstream sections. This pollution is likely of biological origin, via sewage and palm oil mill effluent (POME) discharge, and therefore isotopically indistinguishable from natural C3 plant sources.
Carbon budgets of the Langat and Kelantan River show CO2 degassing to be a significant mechanism of fluvial carbon loss, comprising roughly 50 %, or more, of the total riverine carbon export in both watersheds. The remainder of the river carbon is transported to the ocean in the form of DIC, DOC and POC in broadly comparable proportions. However, the combined riverine carbon export from the Kelantan and Langat Basins amount to 2 % or less of the total carbon sequestration of the watersheds. Thus, most of the sequestered carbon is returned to the atmosphere via respiration, with smaller amounts incorporated into ecosystem biomass .
These results highlight the complexity of carbon cycling in tropical rivers, and agree with previous studies in showing riverine systems to be more than simple conduits of carbon from the land to the ocean.
15
Van, Mooy Benjamin A. S. "Carbon and phosphorus cycling by phylogenetically-defined groups of bacteria in the North Pacific Ocean /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10985.
Testo completo
16
Swanson, Mark Ellyson. "Measurement and modeling of the forest carbon resource in the Nothofagus forests of Tierra del Fuego, Chile /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5491.
Testo completo
17
Nuwer, Jonathan Mark. "Organic matter preservation along a dynamic continental margin : form and fates of sedimentary organic matter /". Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/10999.
Testo completo
18
Braziunas, Thomas F. "Nature and origin of variations in late-glacial and Holocene atmospheric 14C as revealed by global carbon cycle modeling /". Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/6702.
Testo completo
19
Jeschke, David. "A carbon cycle model of forestry in the Russian Far East /". Connect to materials related to title online, 2000. http://www.hps-inc.com/edu/stella/demo%5Fgate.htm.
Testo completoAbstract (sommario):
Thesis (M.A.)--University of Washington, 2000."All variants of the model, 9 scenarios and 31 sensitivity analyses are included on the CD. To run these requires Stella® software. A free runtime version of Stella® is available from the High Performance Systems website at: http://www.hps-inc.com/edu/stella/demo%5Fgate.htm"--Leaf 88. Includes bibliographical references (leaves 70-72).
20
Mielke, Nora. "The role of nitrogen and phosphorus in carbon and nutrient cycling of bryophyte-dominated exosystems". Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231758.
Testo completoAbstract (sommario):
Bryophytes form an important component of northern vegetation communities. Mosses efficiently capture aerially deposited nutrients, restricting nutrient availability to the soil. Given that key ecosystem processes of northern ecosystems are nutrient-limited, understanding nutrient cycling of the moss layer is key to understanding ecosystem nutrient and C cycling in these systems. However, the role of the moss layer in regulating ecosystem-scale nutrient and C cycling, while potentially significant, is largely unknown. The aim of this thesis is to investigate the effect of the relative availability of N and P on aspects of bryophyte nutrient uptake, retention and C acquisition. The hypothesis investigated is that the availability of one nutrient will influence the demand for the other and thereby moss nutrient acquisition and retention mechanisms. To test this hypothesis, various aspects of moss nutrient cycling in response to the relative availability of N and P were investigated. As the C cycle is tightly linked to the N and P cycles, the hypothesis extended to include bryophyte C assimilation and decomposition processes of an arctic tundra. Bryophyte nutrient demand was chiefly governed by the tissue N:P ratio. Consequently, nutrient uptake, both from aerially deposited nutrients and through moss-cyanobacteria N2 fixation, and nutrient losses after a simulated rainfall event were mostly in response to the relative availability of N and P rather than the availability of one nutrient alone. This thesis provides novel evidence that ectohydric mosses have the ability to internally translocate nutrients. In conjunction with efficient nutrient capture, this trait makes mosses strong nutrient sinks which are likely to exert considerable control over ecosystem nutrient cycling. The relative availability of N and P played a role in C uptake of mosses. Through the production of recalcitrant litter and their insulating effect on soil microclimate mosses exerted an influence over ecosystem C cycling.
21
Hotchkiss, Erin R. "Linking exotic snails to carbon cycling in Kelly Warm Springs, Grand Teton National Park". Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1402172011&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Testo completo
22
Turner, Gavin D. "Benthic oxygen exchange across soft and hard bottoms using the new Eddy Correlation technique : case studies from the tropics to the Arctic". Thesis, University of the Highlands and Islands, 2014. https://pure.uhi.ac.uk/portal/en/studentthesis/benthic-oxygen-exchange-across-soft-and-hard-bottoms-using-the-new-eddy-correlation-technique(5335a5b3-7cf9-4913-9715-ab811f7e8a54).html.
Testo completoAbstract (sommario):
Marine sediments play an important role in the global carbon cycle, where they are ultimately important for recycling of carbon. At the sediment-water interface carbon is in constant movement both into and out of the sediment. However some environments are more important for the natural storage of carbon. Over long time scales this process has a role in climate regulation. Measuring the total O2 uptake represents a good proxy for the turnover of organic material at the sediment surface in oxygenated sediments, and equally the release of O2 represents benthic primary production. Many important biological processes are regulated by the availability of O2 at the seabed including: fauna composition and activity, phosphate exchange, nitrogen cycling and burial of organic material. Understanding of the rate and efficiency at which carbon turnover is occurring in marine sediments provides a valuable insight to the regulatory role they play in climate control. Investigation of marine sediments is best done in situ where possible, and the development of benthic “landers” has allowed measurements to be conducted at the sediment-water interface. Most recently, a novel approach known as “Eddy Correlation” (EC) has been developed. It allows quantification of the O2 exchange across any surface from simultaneous measurements of vertical velocity flow and oxygen concentration within the benthic boundary layer. The large sediment area accounted for; the high measuring frequency and the non-invasive nature are theoretical advantages over traditional methods such as benthic chamber incubations and O2 microprofiles. This study has shown that it is difficult to achieve consistent and improved measurements using EC compared to traditional methods due to the complex nature of the equipment and data analysis. Data does suggest that EC can be a strong complimentary tool for benthic carbon exchange studies. This project presents the first use of this technology across a range of benthic environments, from temperate coastal sediments and maerl beds to high-Arctic sediments and sea-ice. The method has allowed accurate quantification of the benthic remineralisation rates and carbon turnover efficiency in the coastal and maerl environments, but less so for the more complex under sea ice and cold Arctic environments. Rates presented agree well with other published studies documenting the use of this state-of-the-art technology.
23
Hagstrom, Kate. "Particle dynamics and shelf-basin interactions in the western Arctic Ocean investigated using radiochemical tracers /". View online ; access limited to URI, 2006. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/fullcit/3239908.
Testo completo
24
Cleary, Meagan B. "Carbon cycling dynamics during succession in sagebrush steppe". Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1362520811&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Testo completo
25
Roberts, Chris David. "Numerical modelling of climate and the carbon cycle during the Cenozoic". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609403.
Testo completo
26
Fraser, Colin J. D. "The hydrology and dissolved organic carbon (DOC) biogeochemistry in a boreal peatland /". Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30383.
Testo completoAbstract (sommario):
A hydrological and biogeochemical study was undertaken at the Mer Bleue bog, Ottawa, Ontario, Canada from May 22, 1998 to May 21, 1999. Basin runoff was generated by groundwater discharge at the peatland margin, and groundwater discharge was controlled by hydraulic gradients and horizontal hydraulic conductivities (Kh). Flux of dissolved organic carbon (DOC) measured at the basin outflow was 8.3 g C m-2 yr-1 and compared to within 23% of DOC flux estimated using a Dupuit approximation of seepage during the ice-free season. Annual DOC flux was 11% of the annual carbon sink.Flownet analysis showed that seasonal patterns of groundwater flow were controlled by boundary condition changes that resulted from precipitation and evapotranspiration events. A pattern of recharge was most common over the hydrological year, but a discharge pattern was observed during a 40 day groundwater flow reversal. Evaluation of the peatland recharge-discharge function using in situ sodium concentrations and a diffusion model revealed that the peatland is a long-term recharge system. It is hypothesized that peatland biogeochemical function is controlled by long-term recharge despite annual occurrence of groundwater flow reversals.
27
Hardison, Amber Kay. "Interactions between macroalgae and the sediment microbial community : nutrient cycling within shallow coastal bays /". W&M ScholarWorks, 2009. http://web.vims.edu/library/Theses/Hardison09.pdf.
Testo completo
28
Bruckner, Monica Zanzola. "Biogeochemistry and hydrology of three alpine proglacial environments resulting from glacier retreat". Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/bruckner/BrucknerM1208.pdf.
Testo completoAbstract (sommario):
Proglacial environments, formed by glacier retreat, exhibit distinct characteristics in discharge, water temperature, water residence time, and dissolved ion, carbon, and suspended sediment concentrations. The unnamed alpine glacier at the headwaters of the Wheaton River, Yukon, Canada, provides an ideal setting to compare deglaciation processes that result in three different proglacial environments. The glacier has evolved from occupying one large catchment (~4 km 2) to two smaller catchments (each ~2 km 2) via glacier thinning and net mass loss, forming two lobes separated by a medial moraine. Field observations revealed neither crevasses nor evidence of subglacial drainage outlets and suggested this glacier had a non-temperate thermal regime with meltwater predominantly flowing from supraglacial and ice marginal sources. Climate and bedrock geology were similar for the subcatchments, providing a natural laboratory to compare deglaciation processes. This study compared the hydrology and biogeochemistry of three outlet streams from this glacier: one stream drained a proglacial lake which is fed by meltwater from the lower west lobe, a second stream drained the upper west lobe, and a third stream was the major drainage outlet for the east lobe. Hydrologic monitoring over the 2006 melt season (June-August) and analyses of water samples for dissolved ion content and carbon indicated that the meltwaters are dominated by Ca 2+ and HCO 3-, which are derived from biogeochemical weathering of crustal materials. The study demonstrated that the presence of the proglacial lake, which acted as a meltwater reservoir, measurably modified meltwater residence time, water temperature, water chemistry, and bacterial biomass relative to the proglacial streams. Rock:water interaction between meltwater and medial morainal sediment and fine-grained, reactive glacial flour suspended in the streams and the lake water column also enhanced biogeochemical weathering within the catchment. Thus, this study provided a small-scale example for how differences in proglacial environments and water flow paths affect headwater hydrology and biogeochemistry. This study was the first of its kind in the Coast Mountains, Yukon, Canada, and results presented here aid in the understanding of how proglacial environments created by climate-induced glacier retreat affect hydrochemistry, hydrology, and carbon dynamics in remote high elevation environments.
29
Dalva, Moshe. "Pathways, patterns and dynamics of dissolved organic carbon in a temperate forested swamp catchment". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59625.
Testo completoAbstract (sommario):
Inputs of DOC in precipitation were low and increased with the passage of rainfall through different canopies. Throughfall, stemflow, leachates from A horizons and litterfall were identified as sources of DOC, while B and C horizons in upland areas provide a sink. Throughfall and stemflow displayed high temporal variability in DOC concentrations, while soil leachates and peat waters exhibited strong seasonal patterns. DOC concentrations in throughfall, stemflow and A horizons were highest in the predominantly coniferous site. In the fall, DOC concentrations from A horizons in the deciduous site were significantly higher than those from the coniferous site.Factors influencing DOC in peat waters are: (1) peat thermal regime, (2) water chemistry, and (3) water table position. Large storms ($>$30 mm precipitation) appear to be the primary factor influencing exports of DOC in streamflow, particularly following dry antecedant soil moisture conditions. Slow rates of water movement through compact deep peats ($>$60 cm depth) and adsorption of DOC in B and C horizons of this catchment obstruct exports of DOC, which over the 5.5 month study period, were minimal in comparison to inputs.
30
Yager, Patricia L. "The microbial fate of carbon in high-latitude seas : impact of the microbial loop on oceanic uptake of CO2 /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/11001.
Testo completo
31
Elifantz, Hila. "Structure and function of microbial communities processing dissolved organic matter in marine environments". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 127 p, 2007. http://proquest.umi.com/pqdlink?did=1251898401&Fmt=7&clientId=79356&RQT=309&VName=PQD.
Testo completo
32
Moore, Lucy. "The moss layer and ectomycorrhizal fungi as drivers of carbon and nutrient cycling in a Scots pine forest". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225948.
Testo completoAbstract (sommario):
In boreal and northern temperate forests, the moss layer and ectomycorrhizal (ECM) fungi play important roles in carbon and nutrient cycling. ECM mycelium is present in the lower parts of the moss layer, but little is currently known about the interaction between these two key components of northern forest ecosystems. This thesis aims to address this knowledge gap and to improve our understanding of the mechanisms through which the moss layer and ECM fungi influence carbon and nutrient cycling. Nutrient transfer between litter and Scots pine seedlings in symbiosis with the ECM fungus Paxillus involutus (Batsch) Fr. was investigated in highly controlled microcosm experiments using, for the first time, intact moss and pine litter. In addition, moss removal plots were established in a Scots pine forest which allowed measurement of processes involved in carbon (C) and nutrient turnover and related variables. There was a close, reciprocal exchange of carbon and nutrients between the host plant and ECM mycelium colonising moss and pine litter (Chapter 2). This was greatly enhanced by intensive colonisation of moss litter, suggesting that mosses provide a key source of nutrients for ECM fungi and may facilitate transfer of photosynthetic C belowground. During almost 2 years of decomposition, moss tissue released more nitrogen (N) but retained more C than pine litter (Chapter 3), further highlighting the importance of the moss layer in providing nutrients for overstorey trees, and in the accumulation of recalcitrant C in soil. In addition to contributing directly to C cycling through inputs of recalcitrant C in litter, the moss layer can influence C cycling indirectly, by increasing soil microbial activity; CO2 efflux was on average 1.4 times greater from soil under the moss layer than from soil covered only in pine litter (Chapter 3). The results suggest that an indirect influence can occur via two pathways: through an insulating effect of the moss layer on soil temperature, and through inputs of dissolved organic carbon (DOC) leached from moss (Chapter 4), both of which may stimulate activity of soil microbes. These findings demonstrate the importance of both the moss layer and ECM fungi in carbon and nutrient cycling in boreal and northern temperate forests, and indicate that mosses provide a key pathway through which nutrients may bypass sequestration in saprotrophic microbial biomass and be transferred directly from plant tissue to ECM fungi and overstorey trees.
33
Arnarson, Thorarinn Sveinn. "Preservation of organic matter in marine sediments : a density fractionation and X-ray photoelectron spectroscopy approach /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/11050.
Testo completo
34
Currey, Pauline M. "Interactions between atmospheric nitrogen deposition and carbon dynamics in peatlands". Thesis, University of Aberdeen, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=165545.
Testo completoAbstract (sommario):
Most undisturbed peatlands sequester carbon, and rising levels of atmospheric nitrogen deposition may have the potential to destabilize this function, possibly resulting in an increased release of carbon dioxide into the atmosphere. It is therefore of vital importance to investigate further the link between atmospheric nitrogen deposition and carbon dynamics in exposed ecosystems such as peatlands. The work described in this thesis aimed to elucidate the impact of increasing nitrogen on aspects of carbon turnover in peatlands. Using a long-term field-based experiment, I tested the effects of 4 years of ammonium and nitrate addition (8, 24 and 56 kg N ha-1 y-1) on the fate of newly photosynthesised carbon by plants and the turnover of labile and recalcitrant carbon. A second set of experiments undertaken in the laboratory assessed the use of plant wax analysis as potential biomarkers of past changes in vegetation and carbon status in peat. Overall, this work has shown that the form of nitrogen (ammonium versus nitrate) is a crucial component of atmospheric pollution and must be taken into consideration when investigating or predicting effects of reactive nitrogen on peatlands. In addition, nitrogen addition affected the fate of newly synthesised carbon differently in Eriophorum vaginatum and Calluna vulgaris, revealing the importance of considering plant traits when investigating environmental changes in terrestrial ecosystems. Furthermore, it has led to the development of an investigative tool for further exploration of the historical effects of atmospheric nitrogen deposition on vegetation an carbon content in peatlands.
35
McEnroe, Nicola A. 1973. "Carbon biogeochemistry of open water pools on an ombrotrophic raised bog, James Bay, Québec, Canada". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115691.
Testo completoAbstract (sommario):
Carbon (C) biogeochemical cycling studies in northern peatlands, in particular the production, consumption, storage and emission of C gases (CO2 and CH4) over space and time between different peatland landforms can help in understanding their current and future role in the global C cycle. In some peatlands, a distinct surface patterning of vegetation, interspersed with open water pools, controls the spatial and temporal variability in CO 2 and CH4 exchange to atmosphere. These open water pools initially develop from shallow, flooded hollows to deeper water bodies and at some point reach a limit in their depth. Observations link pool size to age and spatial location on the peatland surface and over time the proportional cover of pools increases, playing an important role in the long-term peatland C balance.The processes responsible for the production of CO2 and CH 4 in pools remain unexplored. In particular, the contribution of pools to the peatland C balance over the timeframe of the development of a pool complex is not explained and pools are not incorporated into current peatland models. A field study was carried out to examine the exchange of CO2 and CH4 from pools to atmosphere and to explore the spatial and temporal dynamics in CO2, CH4 and DOC storage in pools of different size and spatial location. This was undertaken to improve the understanding of the processes responsible for the generation of CO 2 and CH4 over the timescale of pool development. The empirical study was carried out during spring, summer and fall over two years in an ombrotrophic, raised bog, Quebec, Canada. A modelling component was carried out to examine the contribution of pools to the long-term peatland C balance.
Measurements of dissolved concentrations and emissions of CO2 and CH4 from pool surfaces to atmosphere were different among pools of different sizes and spatial location. Shallow pools had consistently higher emissions of both CO2 and CH4 and higher water column dissolved CO2 and DOC concentrations. Deeper pools had greater concentrations of sediment CH4. Dissolved organic carbon in pools was allochthonous, with a greater concentrations and proportion from higher plant materials in shallow pools, likely contributing to the observed water column CO2 concentrations and greater CO2 emissions.
All pools were supersaturated with dissolved CO2 and CH 4 at the time of sampling, with shallow pools up to eight times atmospheric equilibrium concentrations for CO2 and concentrations were up to one hundred times greater than CH4, comparable to findings in other global freshwater systems. Results suggest that greater decomposition is occurring in shallow pools due to warmer water and basal sediment temperatures and increased light penetration and dissolved oxygen (00) and that greater CH4 production and oxidation accounts for some of the differences reaching a limit at 0.7 m deep. Even though this range of pools are not as deep as pools found on other northern peatlands, the results provide evidence for the potential processes responsible for the generation of CO2 and CH4 emissions to atmosphere and demonstrate that pools have a significant role in the short and long-term peatland C balance. Modelling the hypothesised processes responsible for the generation of CO2 and CH4 shows that if sediment decomposition is the major source of these gases then the dynamical link between pool sediments, C gas production and pool growth has been demonstrated. Ultimately their role as source or sink is largely determined by their size (depth), the proportional cover on the landscape and their rates of C storage in sediments versus rates of C uptake and exchange.
36
Thatcher, Lisa A. "Carbon remineralization and storage in estuarine wetland sediments /". Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/thatcherl/lisathatcher.pdf.
Testo completo
37
Murphy, Paulette P. "The carbonate system in seawater : laboratory and field studies /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/8509.
Testo completo
38
Van, der Merwe Margaretha Johanna. "Influence of hexose-phosphates and carbon cycling on sucrose accumulation in sugarcane spp". Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1257.
Testo completo
39
Juranek, Lauren Wray. "Assessment of Pacific Ocean carbon production and export using measurements of dissolved oxygen isotopes and oxygen/argon gas ratios /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/11055.
Testo completo
40
Culver, Mary Evans. "Applications of chlorophyll a fluorescence in bio-optical models of phytoplankton biomass and productivity / by Mary Evans Culver". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10966.
Testo completo
41
Boys, Roderick Charles James. "The impact of anthropogenic land-use change on soil organic carbon, Oporae Valley, Lake Tutira, New Zealand : a [thesis] submitted to the Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Science in Physical Geography /". ResearchArchive@Victoria e-Thesis, 2008. http://hdl.handle.net/10063/966.
Testo completo
42
Sabetraftar, Karim. "The hydrological flux of organic carbon at the catchment scale : a case study in the Cotter River Catchment, Australia /". View thesis entry in Australian Digital Theses Program, 2005. http://thesis.anu.edu.au/public/adt-ANU20070502.141450/index.html.
Testo completo
43
Bindon, Keren (Keren Ann). "Carbon partitioning in sugarcane internodal tissue with special reference to the insoluble fraction". Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51642.
Testo completoAbstract (sommario):
Thesis (MSc)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: The changes in carbon allocation to sucrose, hexoses, fibre, starch and respiration were investigated in developing internodes of sugarcane. Radiolabelling studies were conducted on internode 3, 6 and 9 tissue, representing three stages of increasing maturity. It was apparent that a high rate of cycling between triose-phosphate and hexose-phosphate occurred. A maximum of 50% of carbon entering triose-phosphates was returned to hexose-phosphate in internode 3 tissue, and this flux decreased with tissue maturity to 30%. Carbon partitioning into sucrose increased from 34% of total 14C uptake in internode 3, to 61% in internodes 6 and 9. In immature tissue, the protein and fibre components were the dominant competing sinks with sucrose for incoming carbon, to which 14 and 16% of carbon were allocated respectively. Increased carbon allocation to sucrose with tissue maturity, coincided with a decrease in partitioning to fibre. This indicated that previous studies had underestimated total carbon allocation to respiration, since the protein component was not considered. In contrast with earlier work, the respiratory pathway was the strongest competitor with sucrose for incoming carbon, even in mature tissue. Between internodes 3 and 6, carbon allocation to total respiration did not change significantly, but decreased 50% in mature tissue. Starch was a weak competitor with sucrose, for incoming carbon, to which a maximum of 2% of 14Cwas allocated in immature tissue. In cane harvested in early spring, radiolabelled maltose was recovered in internode 3 tissue of ripening cane, indicating that concomitant starch synthesis and degradation occurred. The. redistribution of C-1 and C-6 in starch glucose was analysed following feeding of tissue with [1_14C]_and [6_14C]_glucose. Randomization of label in starch indicated that the pathway for carbon movement into sugarcane plastids for starch synthesis is primarily through the triose-phosphate translocator. Finally, this study indicated that radiolabelling of tissue discs is a suitable experimental system to determine carbon flux in sugarcane. During the 3 h labelling period the rate of 14C02 release became linear, indicating that the system approached isotopic steady state between the external and internal glucose pool; and the respiratory processes involved in CO2 release.
AFRIKAANSE OPSOMMING: Die veranderinge in koolstoftoedeling na sukrose, heksoses, vesel, stysel en respirasie is in ontwikkelende internodes van suikerriet ondersoek. Die koolhidraatmetabolisme in internodes 3, 6 en 9, wat drie stadiums van toenemende rypheid verteenwoordig, is met behulp van 14Cmerkingstudies ondersoek. Dit is duidelik dat daar 'n hoë mate van koolstofsirkulering tussen die heksose- en triose-fosfaat poele voorkom. In internode 3 word tot 50% van die koolstofwat in triose-fosfate geïnkorporeer is, weer na heksosefosfaat omgeskakel. Selfs in volwasse weefsel vind daar nog soveel as 30% koolstofsirkukering plaas tussen die twee poele plaas. Koolstoftoedeling vanaf glukose na sukrose het van 34% in internode 3, tot 61% in internodes 6 en 9 toegeneem. Proteïn en selwandkomponente was die belangrikste swelgpunte vir koolstof in onvolwasse weefsel gewees. Namate die weefsel meer volwasse word, word sukrose 'n belangriker swelgpunt. Die koolstoftoedeling aan sukrose is veral ten koste van toedeling aan die selwandkomponente. Die bevinding dat die proteïenpoel 'n sterk swelgpunt is dui aan dat vorige studies die belang van respiratoriese koolstofvloei onderskat het. In teenstelling met vorige aansprake is dit duidelik dat selfs in volwasse weefsel respirasie die grootste swelpunt vir die inkomende organiese koolstof in die internode vorm. Koolstoftoedeling aan respirasie het nie noemenswaardig tussen internodes 3 en 6 verskil nie, maar het met 50% in volwasse weefsel afgeneem. Stysel is deurgaans 'n swak swelgpunt vir koolstof met die hoogste toedeling aan die poel (2%) in die jong weefsel (internode 3) . Na toediening van [U- 14C]-glukose is radioaktief gemerkte maltose gevind in suikerriet wat vroeg in die lente geoes is. Dit dui aan dat gelyktydige afbraak en sintese van stysel plaasgevind het. Die herverdeling van C-l en C-6 in glukose afkomstig van stysel is na toediening van [1_14C]_ en [6-14C]-glukose ontleed. Die ewekansige verspreiding van radioaktiwiteit tussen koolstof 1 en 6 van die glukose in stysel dui aan dat dit hoofsaaklik die triose-fosfaat translokeerder is wat in die plastied verantwoordelik is. Hierdie studie het ook aangetoon dat radioaktiewe merking van weefselsnitte 'n geskikte eksperimentele sisteem is om koolstoftoedeling in suikerriet te ondersoek. Die patroon van 14C02 vrystelling dui daarop dat die weefsel na 'n 3 h inkuberingsperiode isotopiese ewewig tussen die eksterne en interne glukose poele en die respiratoriese prosesse begin bereik het.
44
Wong, Vanessa Ngar Lai. "The effects of salinity and sodicity on soil organic carbon stocks and fluxes /". View thesis entry in Australian Digital Theses Program, 2007. http://thesis.anu.edu.au/public/adt-ANU20080428.223144/index.html.
Testo completo
45
Meiggs, Deidre Janelle. "Development of autonomous in situ techniques to examine the impacts of dynamic forcings on sediment biogeochemistry in highly productive estuarine ecosystems". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37078.
Testo completoAbstract (sommario):
Characterized by high levels of terrestrial organic carbon inputs, estuaries and coastal marshes are among the most productive ecosystems on earth and significantly impact the global carbon cycle. Unfortunately, rates of natural organic matter (NOM) degradation in these environments are difficult to quantify directly due to the complex interaction between microbial respiration processes and abiotic reactions in these sediments, yet estuaries and marshes are considered both net sources and sinks of carbon. Typically carbon remineralization rates are determined by measuring total (TOU) and diffusive (DOU) oxygen uptake fluxes assuming oxygen is the ultimate oxidant. This assumption, however, requires any reduced metabolites produced during microbial respiration to be reoxidized by oxygen. In this study, voltammetric sensors were used to measure terminal electron acceptors or their reduced by-products. By simultaneously considering oxygen as well as anaerobic respiration accepting processes, this study demonstrates that oxygen does not function as the ultimate oxidant in coastal marine sediments due to precipitation and burial of reduced species.
Furthermore, the biogeochemistry of coastal sediments is typically investigated ex situ after collection of sediment cores. However, coastal sediments are subject to complex subsurface hydrological forcing that cannot be accounted for with ex situ measurements. Consequently, in situ approaches are required to better understand the impact of physical processes on sediment biogeochemistry, and two novel in situ voltammetric systems were developed as part of this research. First, a new autonomous benthic lander equipped with a benthic chamber to measure TOU fluxes with a high temporal resolution and a potentiostat and micromanipulator to simultaneously acquire voltammetric depth profiles of the main redox species in pore waters was deployed in a pristine river-fed estuary to characterize the seasonal variability of coastal sediment biogeochemistry and examine the impact of riverine discharge on carbon remineralization processes. Simultaneously, a new electrochemical analyzer equipped with a solar and wind power charging system to ensure continuous monitoring capability and a VHF radio to transmit data was operated remotely via the internet from the Georgia Tech campus to investigate the dynamic coupling between hydrological, chemical, and biological processes in intertidal marsh sediments. Finally, new microelectrodes were deployed in microbial mats to examine the chemical and biological oxidation of sulfide with submillimeter resolution. Typically, only biological processes are considered to oxidize sulfide in these environments. Depth profiles during diel studies were able to demonstrate the formation of thiosulfate as an intermediate oxidation product of sulfide oxidation, suggesting that the chemical oxidation of sulfide is much more prevalent than previously recognized when compared to biological oxidation.
Overall, using a novel in situ sampling technique with high temporal resolution, these studies confirm that biogeochemical processes in coastal sediments vary seasonally. More importantly, these studies also reveal that estuarine sediments are significantly influenced by riverine discharge, demonstrate that the biogeochemical response of these sediments to natural perturbations is rapid, and indicate that respiration processes in continental shelf sediments are controlled by a combination of temperature, supply of inorganic and organic substrates, and hydrological processes, which has important implications regarding the effect of climate change on the biogeochemical cycling of carbon in these environments.
46
Koprivnjak, Jean-François. "Sources, sinks, and fluxes of dissolved organic carbon in subarctic fen catchments". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60045.
Testo completoAbstract (sommario):
The sources, sinks, fluxes, spatial distributions, and temporal variations of dissolved organic carbon (DOC) in subarctic fen catchments as well as the temporal patterns of DOC in streams draining subarctic fen catchments in the region of Schefferville, Quebec were investigated.In June to August sampling, DOC concentrations averaged 17 mg/L in peat water, 2-16 m/L in stream water, 49-56 mg/L in canopy throughfall, 14-19 mg/L in understory throughfall, 122-187 mg/L in stemflow, 25-39 mg/L in lichen and moss mat water, and 35-42 mg/L in soil A horizon water.
Precipitation and canopy and understory throughfall were all significant DOC sources with seasonal DOC fluxes to the forest floor of 0.1-0.4, 0.5-1.3, and 0.8-1.7 g DOC/m$ sp2$ of forest, respectively. The lichen and moss mats and the A soil horizon were also found to be DOC sources, whereas the B soil horizon was a DOC sink. The soil column was estimated to export 0.4-0.5 g DOC/m$ sp2$. Peat, also a DOC source, released 1.2-2.1 g DOC/m$ sp2$.
DOC concentrations in streams draining ten fen catchments were found to be positively correlated with the percentage of fen area in the catchments.
47
Moyer, Ryan P. "Carbon Isotopes (δ13C & Δ14C) and Trace Elements (Ba, Mn, Y) in Small Mountainous Rivers and Coastal Coral Skeletons in Puerto Rico". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1227292285.
Testo completo
48
Gougherty, Steven W. "Exudation Rates and δ13C Signatures of Bottomland Tree Root Soluble Organic Carbon: Relationships to Plant and Environmental Characteristics". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448818110.
Testo completo
49
Dickens, Angela Faith. "Sources, cycling, and preservation of black carbon in sediments from the Washington Margin /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8576.
Testo completo
50
Gontikaki, Evangelia. "Carbon cycling in continental slope sediments : the role of benthic communities". Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=128351.
Testo completoAbstract (sommario):
Previous pulse-chase experiments have revealed a wide diversity of benthic response patterns to organic matter (OM) input depending on environmental setting, benthic community structure and experimental conditions i.e. quantity and quality of the added OM. However, the mechanisms and interaction of environmental and biological factors that produce an observed response pattern are poorly understood. The present thesis set out to improve our current understanding on the set of parameters that determine benthic response patterns. The core of this study was based on two pulse-chase experiments in two bathyal settings: the Faroe-Shetland Channel (FSC) and the SW Cretan slope in the E. Mediterranean (E. Med). The sub-zero temperatures in the FSC enabled the observation of the benthic response in “slow-motion” and showed that the response is not static but instead might go through various “phases”. In the warm E. Med, C processing rates were considerably lower compared to previous measurements in adjacent regions. The discrepancy was attributed to the particularly refractory sedimentary OM at the sampling station with apparent consequences for the physiological state of the bacterial community. Both experiments showed that bacterial metabolism and its regulation is a key factor determining the reaction of the benthic community to OM inputs. This thesis provided further understanding on the short-term fate of organic C in deep-sea sediments but also raised certain issues that could be addressed in future studies.