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1
Levy, Peter E. "Carbon dioxide exchange of Sahelian vegetation." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/12411.
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Measurements of leaf and ecosystems scale CO2 flux were made at the millet, fallow and tiger bush sites at the HAPEX-Sahel Southern supersite. These were analysed in relation to biological and environmental variables. In the five species studied, leaf scale photosynthesis was strongly influenced by photosynthetic photon flux density (Q) and stomatal conductance, and was well described by the non-rectangular hyperbola model of Jarvis, Miranda and Muetzelfeldt (1985). Stem respiration was measured in two species, and increased exponentially with temperature. Stem respiration rates were higher in the wet season than in the dry season and this difference was used to separate growth and maintenance respiration. Effects of Q and sap flow on stem CO2 efflux were observed. A small number of soil respiration measurements were also made. Direct measurements of leaf area index, biomass and canopy structure were made at the millet and fallow sites. Two indirect methods of estimating leaf area index, from hemispherical photographs and measurements of transmitted Q, were used to all three sites. Together with measurements of canopy structure at each site, the measurements of leaf photosynthesis, stomatal conductance and stem soil respiration were used to parameterise two models which predict ecosystem net CO2 flux: a simple one-dimensional "big leaf" model and a complex three-dimensional model "MAESTRO". Model predictions were compared with independent ecosystem flux measurements made by eddy covariance. Generally, both models agreed well with measurements at all three sites. Differences between measurements and predictions were very small in millet and largest in tiger bush, and were attributed to the effect of canopy heterogeneity on eddy covariance measurements and the accuracy with which canopy structure parameters could be estimated.
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Meir, Patrick William. "The exchange of carbon dioxide in tropical forest." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/12648.
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This study investigated the structure of, and carbon dioxide fluxes at, a 'primary' rain forest (PRF) in SW Amazonia, Brazil, and a distributed secondary rain forest (SRF) in SW Cameroon. The total above-ground biomass and leaf area index (LAI) at PRF were respectively 220 (±95% c.l. 48) Mg ha-1 and 4.0 (±95% c.l. 0.7) m2 m-2, and at SRF 90 (±95% c.l. 9.4) Mg ha-1 and 4.4 (±95% c.l. 0.9) m2 m-2. A novel method was devised to quantify the vertical profile in LAI: SRF was distinguished from PRF by a higher concentration of leaf area near the ground. Three methods were used to determine the flux of CO2 from soil and gave overall agreement (static and dynamic chambers, and eddy covariance). The mean soil efflux in PRF and SRF was respectively 5.5 μmol m-2 s-1 (±95% c.l. 0.2; n = 42) and 4.5 μmol m-2 s-1 (±95% c.l. 0.2; n = 178) at 20 - 24 °C. The temperature response was higher in PRF than SRF (Q10 = 2.3 vs 1.9). Soil efflux rates were also obtained from cerrado vegetation in central Brazil, where the efflux was 3.2 μmol m-2 s-1 (±95% c.l. 0.2; n = 10) the Q10 1.6, at 16 - 23 °C. Heterogeneity in emission was higher in SRF than in PRF and could be described by a non-linear model incorporating the variables: soil temperature, organic carbon and total nitrogen (r2 = 0.82). Carbon was the most important variable determining respiration in SRF; soil moisture was not limiting. There was no observable effect of season on efflux rates in either rain forest, but a decline occurred in cerrado during the dry season. Effluxes of CO2 were measured from stems and branches of diameter 0.002 m - 1.6 m in 24 species in PRF and 17 species in SRF; emission rates were 0.1 - 3.3 μmol m-2 s -1 with a Q10 of 1.8 in PRF, and 0.2 - 5.2 μmol m-2 s -1 with a Q10 of 1.6 in SRF. Maintenance respiration was 80% and construction respiration 20% of total woody tissue respiration (Rt) in SRF. A functional model described the relationship between Rt and diameter in SRF better than a purely empirical one (r2 = 0.66). A novel method was devised in estimate sap CO2 concentrations which in SRF were 1.2 - 11.0 nmol 1-1 for Distemonanthus benthamianus and Musanga cecropioides. Sap CO2 levels were highly sensitive to sap pH, and represented 1 - 30% of cuvette-measured leaf photosynthesis. Maintenance leaf respiration (Rm) was measured through the vertical profile during the night in PRF and SRF. Rm increased with height at both sites: 0.2 in PRF vs 0.3 in SRF at 1.5 m and 0.5 in PRF vs 0.9 in SRF at 26 m (values normalised to 22 °C, units: μmol m-2 s-1). Leaf nitrogen and potassium concentrations (Nleaf and Pleaf) declined with height in the canopy. Pleaf concentrations were higher in SRF than PRF where Pleaf appeared to limit respiration. Rm was not significantly related.
3
Coetzee, Johannes Wilhelm. "The ion exchange phenomenon of acetylene black." Thesis, Cape Technikon, 1996. http://hdl.handle.net/20.500.11838/909.
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Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town,1996Acetylene Black IACB) IS a pure form of carbon which is used in the battery, plastics, printing and rubber industries. It is extensively used in the battery industry to absorb electrolyte and to lower the electrical resistance of dry cell batteries. It is the attempt of this thesis, to investigate the surface characteristics '---------._-- -,- ...• -...•--- .. ------.. _.. --- "'- and structure of ACB by using it as an adsorbent for cyanide complexes, in particular gold cyanide. The thesis is predominantly aimed at identifying the mechanism of metal cyanide adsorption onto ACB, viz. ion exchange and/or physical adsorption. In order to quantify the mechanism of adsorption, comparative studies with other adsorbents currently used in the mining industry, such as activated carbon, were conducted. These studies revealed various similarities in the metal adsorption process between ACB and activated carbon, thus indicating physical adsorption rather than ion exchange to be the dominant mechanism for metal adsorption from solution. The rate of metal adsorption onto acetylene black was relatively fast compared to activated carbon. Furthermore, adsorption profiles revealed that intraparticle diffusion was negligible when a metal was adsorbed onto ACB from solution. This indicates that acetylene black has a predominantly amorphous structure, although X-ray diffractrometry indicates a certain degree of graphitisation associated with ACB. The small surface area of ACB, together with the lack of intraparticle diffusion, resulted in the rapid attainment of the equilibrium metal loading on ACB. Moreover, this equilibrium metal loading was far less than that of activated carbon and ionexchange resin. While pH, temperature and strong oxidizing agents had a marked effect on the adsorption profile of metal cyanides onto ACB, the effect of oxygen enrichment and organic solvents was negligible. Furthermore, the adsorption of gold onto ACB is best explained by a Freundlich-type isotherm. As is the case with activated carbon and ion exchange resin, gold is eluted from ACB by a NaOH solution. It was also found that the elution efficiency is influenced by a change in temperature. Changes in operating variables in the production of ACB had an effect on the absorption stiffness of the product. Both an increase in acetylene feed rate and operating temperature reduced the absorption stiffness of the product.
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Harry, I. D. "Modification and characterisation of carbon fibre ion exchange media." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/14123.
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This thesis examines the use of electrochemically treated viscose rayon based activated carbon cloth (ACC) for the removal of metal ions from aqueous effluent streams. Two types of treatment were performed: (i) electrochemical oxidation and (ii) electrochemical reduction to enhance cation and anion sorption capacities of the ACC, respectively. Electrochemical oxidation resulted in a loss of 61% BET surface area due to blockage of pores through formation of carboxylic acidic groups but its cation exchange capacity and oxygen content increased by 365% and 121%, respectively. The optimum constant current at which a combination of applied current and oxidation time at any extent of oxidation to produce ACC of maximum cation exchange capacity was found to be 1.1 A, with voltage of 4.2 V and current density of 0.8 mA/m2. Batch sorption experiments showed that the maximum copper and lead sorption capacities for electrochemically oxidised ACC increased 17 and 4 times, respectively, for noncompetitive sorption and 8.8 and 8.6 times, respectively for competitive sorption. Therefore, electrochemically oxidised ACC is an effective adsorbent for treating aqueous solution contaminated with copper/lead in both single component and multi-component systems. Industrial wastewaters are multicomponent systems, therefore, electrochemical oxidation of ACC is an efficient way of enhancing lead and copper ions sorptive capacity for industrial wastewater treatment. Electrochemical reduction resulted in a loss of 28% BET surface area due to formation of ether groups but its anion exchange capacity increased by 292%. The optimum constant current at which a combination of applied current and reduction time at any extent of reduction to produce ACC of maximum anion exchange capacity was found to be 5.5 A, with voltage of 9.8 V and current density of 6.4 mA/m2. Batch sorption experiments showed that the maximum chromium(VI) sorption capacity for electrochemically reduced ACC increased 2.12 times, with highest maximum chromium(VI) sorption capacity of 3.8 mmol/g at solution pH 4. Most industrial wastewaters contaminated with chromium(VI) are highly acidic, therefore, electrochemical reduction of ACC is an efficient way of enhancing chromium(VI) sorptive capacity for industrial wastewater treatment.
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Hunt, S. "Photosynthetic gas exchange and carbon metabolism in Moricandia arvensis." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356607.
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Matsuo, Naoko. "Evaluation of Leaf Gas Exchange Using Carbon Isotopic Analysis." Kyoto University, 2003. http://hdl.handle.net/2433/148980.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第10254号
農博第1326号
新制||農||866(附属図書館)
学位論文||H15||N3775(農学部図書室)
UT51-2003-H675
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 谷 誠, 教授 櫻谷 哲夫, 教授 森本 幸裕
学位規則第4条第1項該当
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Glenn, Aaron James, and University of Lethbridge Faculty of Arts and Science. "Growing season carbon dioxide exchange of two contrasting peatland ecosystems." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2005, 2005. http://hdl.handle.net/10133/259.
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The CO2 flux of two peatlands in northern Alberta was examind during the 2004 growing season using eddy covariance measurements of net ecosystem exchange (NEE), chamber measurements of total ecosystem respiration, and empirical models driven by meteorological inputs. The two ecosystems, a poor fen and an extreme-rich fen, differed significantly in plant species composition, leaf area index, aboveground biomass and surface water chemistry. The mean diurnal pattern of NEE at the peak of the season was similar between the sites, however, the extreme-rich fen had a higher photosynthetic and respiratory capacity than the poor fen. Over the 6 month study, the poor fen was shown to accumulate between 2 to 3 times more carbon than the extreme-rich fen despite having a lower photosynthetic capacity. The evergreen nature of the poor fen site allowed for a longer season of net CO2 uptake than the deciduous species that dominated the extreme-rich fen.xii, 126 leaves : ill. (some col.) ; 29 cm.
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Singleton-Jones, Paul. "Elevated carbon dioxide and gas exchange in groundnut and sorghum." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243686.
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Beckley, Philip D. "Gas exchange during apneic oxygenation with extracorporeal carbon dioxide removal /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487265555440255.
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Carlson, Peter John, and University of Lethbridge Faculty of Arts and Science. "Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2000, 2000. http://hdl.handle.net/10133/115.
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Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland by Peter Carlson Chairperson of the Supervisory Committee: Professor Lawrence Flanagan Department of Biological Science Eddy covariance measurements were carried out to document the seasonal and inter-annual variation in CO2 flux in a mixed prairie grassland. There was very different net ecosystem carbon exchange between the two years of study. In 1998 the maximum net ecosystem carbon exchange was 4.95 g C m-2d-1, compared to 2.50 g C m-2d-1 in 1999. The most important environment control on CO2 uptake was volumetric soil moisture content through its affect on leaf area index. There was evidence of stomatal limitation of CO2 uptake, during periods of atmospheric drought. The total seasonal net ecosystem carbon gain for 1998 was 190.0 g C m-2, compared with 46.8 g C m-2 in 1999. This grassland is a large carbon sink in a growing season of above normal precipitation. In a year of normal summer precipitation, this grassland is a small carbon sink, replacing slightly more carbon than is lost through winter respiration.xi, 99 leaves : ill. ; 28 cm.
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Carlson, Peter John. "Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0029/MQ61038.pdf.
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Edwards, Eric Alan. "Water, Energy and Carbon Dioxide Exchange of a Riparian Mesquite Woodland." Thesis, The University of Arizona, 2002. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0090_sip1_w.pdf&type=application/pdf.
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Oyarce, Alejandro. "Electrode degradation in proton exchange membrane fuel cells." Doctoral thesis, KTH, Tillämpad elektrokemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133437.
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The topic of this thesis is the degradation of fuel cell electrodes in proton exchange membrane fuel cells (PEMFCs). In particular, the degradation associated with localized fuel starvation, which is often encountered during start-ups and shut-downs (SUs/SDs) of PEMFCs. At SU/SD, O2 and H2 usually coexist in the anode compartment. This situation forces the opposite electrode, i.e. the cathode, to very high potentials, resulting in the corrosion of the carbon supporting the catalyst, referred to as carbon corrosion. The aim of this thesis has been to develop methods, materials and strategies to address the issues associated to carbon corrosion in PEMFC.The extent of catalyst degradation is commonly evaluated determining the electrochemically active surface area (ECSA) of fuel cell electrode. Therefore, it was considered important to study the effect of RH, temperature and type of accelerated degradation test (ADT) on the ECSA. Low RH decreases the ECSA of the electrode, attributed to re-structuring the ionomer and loss of contact with the catalyst.In the search for more durable supports, we evaluated different accelerated degradation tests (ADTs) for carbon corrosion. Potentiostatic holds at 1.2 V vs. RHE were found to be too mild. Potentiostatic holds at 1.4 V vs. RHE were found to induce a large degree of reversibility, also attributed to ionomer re-structuring. Triangle-wave potential cycling was found to irreversibly degrade the electrode within a reasonable amount of time, closely simulating SU/SD conditions.Corrosion of carbon-based supports not only degrades the catalyst by lowering the ECSA, but also has a profound effect on the electrode morphology. Decreased electrode porosity, increased agglomerate size and ionomer enrichment all contribute to the degradation of the mass-transport properties of the cathode. Graphitized carbon fibers were found to be 5 times more corrosion resistant than conventional carbons, primarily attributed to their lower surface area. Furthermore, fibers were found to better maintain the integrity of the electrode morphology, generally showing less degradation of the mass-transport losses. Different system strategies for shut-down were evaluated. Not doing anything to the fuel cell during shut-downs is detrimental for the fuel cell. O2 consumption with a load and H2 purge of the cathode were found to give around 100 times lower degradation rates compared to not doing anything and almost 10 times lower degradation rate than a simple air purge of the anode. Finally, in-situ measurements of contact resistance showed that the contact resistance between GDL and BPP is highly dynamic and changes with operating conditions.Denna doktorsavhandling behandlar degraderingen av polymerelektrolytbränslecellselektroder. polymerelektrolytbränslecellselektroder. Den handlar särskilt om nedbrytningen av elektroden kopplad till en degraderingsmekanism som heter ”localized fuel starvation” oftast närvarande vid uppstart och nedstängning av bränslecellen. Vid start och stopp kan syrgas och vätgas förekomma samtidigt i anoden. Detta leder till väldigt höga elektrodpotentialer i katoden. Resultatet av detta är att kolbaserade katalysatorbärare korroderar och att bränslecellens livslängd förkortas. Målet med avhandlingen har varit att utveckla metoder, material och strategier för att både öka förståelsen av denna degraderingsmekanism och för att maximera katalysatorbärarens livslängd.Ett vanligt tillvägagångsätt för att bestämma graden av katalysatorns degradering är genom mätning av den elektrokemiskt aktiva ytan hos bränslecellselektroderna. I denna avhandling har dessutom effekten av temperatur och relativ fukthalt studerats. Låga fukthalter minskar den aktiva ytan hos elektroden, vilket sannolikt orsakas av en omstrukturering av jonomeren och av kontaktförlust mellan jonomer och katalysator.Olika accelererade degraderingstester för kolkorrosion har använts. Potentiostatiska tester vid 1.2 V mot RHE visade sig vara för milda. Potentiostatiska tester vid 1.4 V mot RHE visade sig däremot medföra en hög grad av reversibilitet, som också den tros vara orsakad av en omstrukturering av jonomeren. Cykling av elektrodpotentialen degraderade istället elektroden irreversibelt, inom rimlig tid och kunde väldigt nära simulera förhållandena vid uppstart och nedstängning.Korrosionen av katalysatorbäraren medför degradering av katalysatorn och har också en stor inverkan på elektrodens morfologi. En minskad elektrodporositet, en ökad agglomeratstorlek och en anrikning av jonomeren gör att elektrodens masstransportegenskaper försämras. Grafitiska kolfibrer visade sig vara mer resistenta mot kolkorrosion än konventionella kol, främst p.g.a. deras låga ytarea. Grafitiska kolfibrer visade också en förmåga att bättre bibehålla elektrodens morfologi efter accelererade tester, vilket resulterade i lägre masstransportförluster.Olika systemstrategier för nedstängning jämfördes. Att inte göra något under nedstängning är mycket skadligt för bränslecellen. Förbrukning av syre med en last och spolning av katoden med vätgas visade 100 gånger lägre degraderingshastighet av bränslecellsprestanda jämfört med att inte göra något alls och 10 gånger lägre degraderingshastighet jämfört med spolning av anoden med luft. In-situ kontaktresistansmätningar visade att kontaktresistansen mellan bipolära plattor och GDL är dynamisk och kan ändras beroende på driftförhållandena.
QC 20131104
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Wu, Jianghua. "Simulating northern peatland-atmosphere carbon dioxide exchange with changes in climate." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86815.
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About half of the global wetlands are located between 50-70° N, where climate change is projected to be greater than other regions. More than 95% of northern wetlands are peatlands. The majority of peatlands accumulate soil carbon (C) because, on average, net primary production (NPP) exceeds decomposition. Peatlands store ~ 450 G t soil carbon (1Gt C=1015 g C), a mass equivalent to about 20% of global terrestrial soil C, or half of atmospheric C. The carbon exchange between peatlands and the atmosphere is sensitive to climate variability and change because of the tight coupling with hydrology and ecosystem biogeochemistry. A critical question of this thesis is "Will northern peatlands continue to function as C sink under the projected climate change?"I use a modelling approach to answer this question. Firstly, a peatland C cycling model, the McGill Wetland Model (MWM), originally developed to simulate the C dynamics of ombrotrophic bogs, was modified, parameterized and evaluated for the simulation of the CO2 biogeochemistry of fens. Three modifications were made: (1) a function describing the impact of soil moisture on the optimal gross primary production (GPP); (2) a scheme to partition the peat profile into oxic and anoxic C compartments based on the effective root depth as a function of daily sedge NPP; and (3) a modified function describing the fen moss water dynamics. Secondly, I have examined the effect of bog microtopography on the simulation of ecosystem-level C cycling and found model processes scale linearly, so "parameter" upscaling can be used in regional scale assessments. Thirdly, I successfully evaluated a coupled Wetland version of Canadian Land Surface Scheme (CLASS3W) and MWM (called CLASS3W-MWM) for bogs and fens. The sensitivity analysis indicates that northern peatlands are thermally and hydrologically conservative and the combination of changes in temperature, precipitation and double CO2 concentration is much different than the sensitivity of peatlands to each environmental variable on their own.
Finally, I used CLASS3W-MWM to do a first-order experiment on how the CO2 exchange in northern peatlands might change under the changing climate. For future climate, I adjusted the site "measured" climate variables by the climate anomalies estimated by the CCCma-GCM3.0 for three time slices (2030, 2060 and 2100) using four different climate scenarios (A1B, A2, B1 and Commit). These simulations showed that bogs and fens have significantly different responses to climate change, particularly that fens are more sensitive to environmental change than bogs. At 2100, the bog remains a C sink for all the climate scenarios assessed because a significant increase in GPP still offset, to a smaller extent, the large increase in total ecosystem respiration (TER). However, by 2100, the fen switches to a C source for two scenarios (A1B and A2), due to a dramatic decrease in GPP and a significant increase in TER resulting from water stress linked to a large drop of water table depth.
Environ la moitié de l'ensemble des tourbières sont situées entre 50-70° N, là où les changements climatique prévus risquent d'être plus important que dans les autres régions. Plus de 95% des milieux humides nordiques sont des tourbières. La majorité des tourbières accumule du carbone (C) puisqu'en moyenne, la production nette primaire (NPP) excède la décomposition. Les tourbières accumulent environ 450 G t de C (1Gt C=1015 g C), une masse équivalente à environ 20% du C terrestre, ou la moitié du C atmosphérique. L'échange de C entre les tourbières et l'atmosphère est sensible aux changements climatiques et varie en fonction du lien entre leur hydrologie et la biogéochimie de l'écosystème. Une des questions critiques de cette thèse est « est-ce que les tourbières du nord demeureront des puits de C malgré les changements climatiques projetés? ».
J'utilise une approche de modélisation pour répondre à cette question. Premièrement, le modèle représentant le cycle du C dans les tourbière, le McGill Wetland Model (MWM), développé à l'origine pour simuler la dynamique du C dans les tourbières ombrotrophiques, a été modifié et les paramètres ajustés et évalués afin de simuler la biogéochimie du dioxide de carbone (CO2) des tourbières oligotrophiques. Trois modifications ont été faites : (1) une fonction décrivant l'impact de l'humidité du sol sur la production primaire brute (GPP) optimale; (2) un schéma pour partitionner le profil de la tourbière selon les compartiments oxiques et anoxiques du C basé sur la profondeur effective des racines en fonction de la NPP journalière du carex; et (3) une fonction modifiée décrivant la dynamique de l'eau de la tourbe en milieu oligotrophique. Deuxièmement, j'ai examiné l'effet de la microtopographie de la tourbière sur la simulation du cycle du C à l'échelle de l'écosystème et trouvé les processus du modèle à l'échelle linéaire, pouvant ainsi modifier les paramètres en changeant l'échelle utilisée pour l'évaluation à l'échelle régionale. Troisièmement, j'ai évalué avec succès une version couplée du modèle Canadian Land Surface Scheme (CLASS3W) et MWM, nommé (CLASS3W-MWM) pour les types de tourbières ombrotrophiques et oligotrophiques. L'analyse de sensibilité indique que les tourbières du nord sont conservatrices au niveau thermal et hydrologique et la combinaison du changement de température, de précipitation et une double concentration de CO2 est très différente par rapport à la sensibilité de chaque variable individuellement.
Finalement, j'ai utilisé le CLASS3W-MWM pour faire une expérience de premièr-ordre vérifiant comment l'échange de CO2 dans les tourbières du nord peuvent être modifiés sous un climat changeant. Pour les climats futurs, j'ai ajusté la variable climatique du site « mesuré » par les anomalies climatiques estimées par le CCma-GCM3.0 pour trois périodes de temps (2030, 2060 et 2100) en utilisant quatre différents scénarios climatiques (A1B, A2, B1 et Commit). Ces simulations ont montré que les tourbières oligotrophiques et ombrotrophiques ont des réponses significativement différentes aux changements climatiques, particulièrement les tourbières oligotrophiques, qui sont plus sensibles au changements environnementaux que les tourbières ombrotrophiques. En 2100, la tourbière ombrotrophique demeure un puits de C durant la totalité du scénario puisqu'une augmentation significative de la GPP compensait toujours, même si de manière moindre, l'augmentation importante de la respiration de l'écosystème (TER). Toutefois, en 2100, la tourbière oligotrophique est devenue une source de C pour deux scénarios (A1B et A2), dû à une diminution drastique de la GPP et une augmentation du TER résultant du stress hydrique lié à une grande diminution de la profondeur de la nappe phréatique. fr
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Crombie, Stephanie. "Carbon and water vapour exchange in a temperate fresh water marsh." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114374.
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The ability of wetlands to sequester carbon has given them a considerable amount of attention, especially in light of global climate change. To date, many wetland studies have focused on peatlands, however very few studies have been conducted on marshes. This study used the eddy covariance (EC) technique to measure net ecosystem carbon exchange (NEE) and energy exchange at a temperate freshwater cattail marsh near Ottawa, Canada. The objectives of the study were to use a four year dataset to determine the environmental controls on the variability of carbon and water vapour exchange. The annual cumulative NEE was on average -246 ± 31 gCm-2yr-1 ranging from -216 to -260 gCm-2yr-1. The variability in accumulation between years was a result of the timing of spring and fall transitions in the carbon uptake and the length of the growing seasons, each of which were determined by prevailing weather conditions. Evaluation of the interannual variability indicated that the marsh may be sensitive to carbon (C) losses through enhanced respiration under warmer autumn periods. Maximum daily average values of evapotranspiration (ET) reached 10.75, 9.07, 11.70 and 8.36 mm day-1 in 2005, 2006, 2007 and 2008, respectively. Bowen ratio values varied seasonally with values well below unity during the growing season (May to October) illustrating the dominance of latent heat. Evaluation of the evaporative fraction and Priestley-Taylor α indicated the seasonal importance of ET and mid-season high values of the decoupling coefficient (Ω) indicated that the marsh ET is radiatively driven owing its smooth aerodynamic surface and abundance of water. Overall, the marsh ecosystem was a large annual sink for CO2 as compared to other wetland ecosystems and ET rates were highly dependent on radiative input.La capacité des milieux humides à séquestrer du carbone a beaucoup attiré l'attention, notamment dans le contexte des changements climatiques. À ce jour, bien que plusieurs études aient été menées sur les tourbières, très peu portent sur les marais. Cette étude a utilisé la technique de covariance des turbulences afin de mesurer l'échange écosystémique net (EEN) de CO2 et l'échange d'énergie d'un marécage de quenouilles de l'est de l'Ontario, Canada. Les objectifs de cette étude étaient d'utiliser un ensemble de données de quatre ans afin de déterminer les contrôles environnementaux sur la variabilité des échanges de carbone et de vapeur d'eau. Le EEN annuel cumulé était en moyenne de -246 ± 26,8 gCm-2a-1 allant de -216 à -260 gCm-2a-1. La variabilité de l'accumulation entre les années était le résultat de la synchronisation du printemps et de l'automne au niveau de l'absorption du carbone et de la longueur des saisons de croissance, chacune ayant été déterminée par les conditions météorologiques qui prévalaient. L'étude de la variabilité interannuelle a indiqué que le marécage pourrait être sensible aux pertes de C causées par une augmentation de la respiration au cours de périodes plus chaudes d'automne. Les valeurs moyennes quotidiennes maximales d'évapotranspiration (ET) ont atteint 10,75, 9,07, 11,70 et 8,36 mm jour-1 en 2005, 2006, 2007 et 2008 respectivement. Les valeurs du rapport de Bowen variaient selon la saison, avec des valeurs bien en dessous de l'unité pendant la saison de croissance (mai à octobre), illustrant la dominance de la chaleur latente. Une évaluation de la fraction d'évaporation et du facteur α de Priestley-Taylor indiquaient l'importance saisonnière de l'ET et les valeurs élevées de mi-saison du facteur de découplage (Ω) indiquaient que l'ET du marais est dominé par les radiations en raison de sa surface aérodynamique lisse et de l'abondance d'eau. Dans l'ensemble, l'écosystème du marais était un grand puits de carbone annuel par rapport aux écosystèmes de tourbière et les taux d'ET étaient fortement dépendants de l'apport radiatif.
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Ozcelik, Oguz. "Effects of altered body gas stores on pulmonary exchange dynamics." Thesis, St George's, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314210.
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Öquist, Mats. "Northern peatland carbon biogeochemistry : the influence of vascular plants and edaphic factors on carbon dioxide and methane exchange /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek729s.pdf.
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Guvenatam, Burcu. "Development Of Different Carbon Supports For Proton Exchange Membrane Fuel Cell Electrocatalysts." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612376/index.pdf.
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Proton exchange membrane (PEM) fuel cell technology is promissing alternative solution to today&rsquos energy concerns providing clean environment and efficient system. Decreasing platinum (Pt) content of fuel cell is one of the main goals to reduce high costs of fuel cell technology in the way of commercialization. In this target, porous carbons provide an alternative solution as a support material for fuel cell electrocatalysts. It is also essential to increase surface area of carbon support material to have well dispersion of the Pt nanoparticles. The aim of this thesis is to synthesize mesoporous carbon supports named as hollow core mesoporous shell (HCMS) carbon and prepare their corresponding electrocatalysts with platinum impregnation method. HCMS carbon supports were synthesized by using two different carbon sources. As a first approach, phenol/paraformaldehyde couples were used and carbon source exhibited 1053 m 2 /g BET surface area and 1.046 nm BJH adsorption pore diameter. Second approach was to use divinylbenzene (DVB) as a carbon source with an initiator named as azo bis isobuytronitrile (AIBN) differing synthesis criteria. It is observed that using AIBN/DVB, pore sizes increased up to 3.44 nm. Platinum impregnation was conducted by microwave irradiation method using hydrogen hexachloroplatinate (IV) hydrate as a platinum precursor. The first achievement was to increase platinum loading up to 44 wt % on commercial Vulcan XC 72 by using ethylene glycol as a reducing agent. Using different reducing agents such as hydrazine, sodium borohydrate with a combination of ethylene glycol, platinum loading reached up to 34 wt % on HCMS carbon support. Accordingly, 34 wt %, 32 wt % and 28 wt % Pt/HCMS carbon supported electrodes preparation was achieved. The sizes of the platinum nanoparticles were calculated by XRD analysis as 4 nm, 4.2 nm and 4.5 nm for 28 wt %, 32 wt % and 34 wt % Pt/HCMS carbon supported electrodes respectively. Characterizations of catalysts were performed by ex situ (N 2 adsorption, TGA, SEM, TEM and Cyclic Voltammetry) and in situ (PEMFC tests) analysis.
19
Rodrigues, Aida. "The effects of carbon monoxide contamination on proton-exchange membrane fuel cells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22388.pdf.
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Yepez-Gonzalez, Enrico Arturo. "Sources and Dynamics of Carbon Dioxide Exchange and Evapotranspiration in Semiarid Environments." Diss., Tucson, Arizona : University of Arizona, 2006. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1566%5F1%5Fm.pdf&type=application/pdf.
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Beeming, Brendan Albert. "Synthesis and characterisation of carbon supported gold catalysts prepared by ion-exchange." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5349.
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Includes abstract.Includes bibliographical references (leaves 86-97).
Gold has been previously overlooked as a catalyst, mainly because the metal has been regarded as catalytically inert, and was tested as large aggregates, and not as nanocrystallites. Large crystallites of gold do not exhibit significant catalytic activity, and if they do, their activity is small compared with platinum group metals. The recent interest in gold as a catalyst has been fuelled by the development of processes to deposit gold on a catalyst support as nano-crystallites (Prati and Martra, 1999). Gold catalysts with nano-crystallites on selected supports have been shown to exhibit high activity for mainly redox reactions (Gluhoi, 2005; Hutchings, 2005). These catalysts have recently been attracting attention as they can be used at near ambient conditions, which allows for cheaper and more environmentally friendly processes. Glucose yielding gluconic acid is an industrially important reaction (Biella et aI., 2002). Gluconic acid and its salts are used as water-soluble cleansing agents or as additives in food and beverages which makes these products important in industrial applications (Kirk-Othmer, 1995). Industrially, the aerobic oxidation of glucose is an enzyme catalysed process. However, due to the low productivity of the glucose fermentation process, the development of a chemical route is of interest. Gold catalysis provides a promising alternative route which can be applied at mild conditions.
22
McAleer, Adam David Anthony. "Carbon dioxide and methane exchange from restored mires in Exmoor National Park." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702878.
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McCracken, Peter J. "Turbulent exchange of momentum and carbon dioxide of a Sitka spruce plantation." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/15323.
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Our knowledge of the global carbon budget is at present insufficient to predict reliably the possible consequences of rising CO2 levels on the climate and on ecosystems. Attempts to close the global carbon budget have indicated that a major sink for CO2 may exist in the boreal forests of the northern hemisphere, (Tans et al., 1990). This thesis reports on field experiments which were undertaken to investigate the turbulent exchange of mass, energy and momentum in a northern hemisphere coniferous forest, with special attention to the exchange of carbon dioxide. The eddy covariance technique was used to measure mass, energy and momentum fluxes above and within a Sitka spruce, (Picea sitchensis (Bong.) Carr.), plantation in South West Scotland. The forest had a mean height, h, of 15 m, was densely planted and unthinned. Measurements were made at heights of 1.2h, 0.7h and 0.1h, where the heights within the canopy corresponded to the lower canopy crown and the dead branch trunkspace, respectively. The upper canopy was found to be efficient at attenuating momentum, with momentum fluxes at 0.7h being only 2 - 3% of those at 1.2h. Spectral slopes of velocity and scalar quantities were considerably steeper than expected from Similarity theory indicating a more rapid dissipation of larger scale motions than above the canopy. Evidence was found to support the existence of large, intermittent and energetic structures dominating the turbulent exchange in the forest. Eularian integral time scales for streamwise (Lu) and vertical (Lw) velocities were calculated at 1.2h as ~ h and ~ 0.2h, respectively. A momentum quadrant analysis indicated that ~ 50% of momentum flux, 21 - 47% of CO_2 flux and 23 - 44% of sensible heat flux at 1.2h was accounted for by events with instantaneous momentum fluxes greater than four times the mean value, which occurred only 5 - 12% of the time.
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Kokic, Jovana. "Gas Exchange over Aquatic Interfaces and its Importance for Greenhouse Gas Emission." Doctoral thesis, Uppsala universitet, Limnologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-307792.
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Aquatic ecosystems play a substantial role in global cycling of carbon (C), despite covering only about 4% of the earth surface. They emit large amounts of greenhouse gases (GHG) to the atmosphere, comparable to the amount of C stored annually in terrestrial ecosystems. In addition, C can be buried in lake sediments. Headwater systems are located at the interface of the terrestrial and aquatic environment, and are first in line to process terrestrial C and throughout its journey through the aquatic continuum. The uncertainties in global estimates of aquatic GHG emissions are largely related to these headwater systems, as they are highly variable in time and space, and underrepresented in global assessments. The overall aim of this thesis was therefore to study GHG exchange between sediment, water and air in headwater systems, from both an ecosystem perspective and at the small scale of physical drivers of gas exchange. This thesis demonstrates that carbon dioxide (CO2) emission from headwater systems, especially streams, was the main pathway of C loss from surface waters from a lake catchment. Of the total aquatic CO2-emission of the catchment, 65% originated from stream systems that covered only 0.1% of the total catchment area. The gas transfer velocity (k) was the main driver of stream CO2-emission, but there was a high variability in k on small spatial scales (meters). This variability may have implications for upscaling GHG emissions, especially when using scaled k estimates. Lake sediments only contributed 16% to total lake C emission, but in reality, sediment C emission is probably even lower because experimentally determined sediment C flux returns high estimates that are biased since artificially induced turbulence enhances C flux rates beyond in-situ conditions. When sediment C flux is estimated in-situ, in natural bottom water turbulence conditions, flux rates were lower than those estimated experimentally. Conclusively, this thesis shows that GHG emissions from small aquatic ecosystems are dominant over other aquatic C fluxes and that our current knowledge regarding the physical processes controlling gas exchange from different small aquatic systems is limited, implying an inherent uncertainty of GHG emission estimates from small aquatic ecosystems.
25
Winchell, Taylor S., David M. Barnard, Russell K. Monson, Sean P. Burns, and Noah P. Molotch. "Earlier snowmelt reduces atmospheric carbon uptake in midlatitude subalpine forests." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/621684.
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Previous work demonstrates conflicting evidence regarding the influence of snowmelt timing on forest net ecosystem exchange (NEE). Based on 15years of eddy covariance measurements in Colorado, years with earlier snowmelt exhibited less net carbon uptake during the snow ablation period, which is a period of high potential for productivity. Earlier snowmelt aligned with colder periods of the seasonal air temperature cycle relative to later snowmelt. We found that the colder ablation-period air temperatures during these early snowmelt years lead to reduced rates of daily NEE. Hence, earlier snowmelt associated with climate warming, counterintuitively, leads to colder atmospheric temperatures during the snow ablation period and concomitantly reduced rates of net carbon uptake. Using a multilinear-regression (R-2=0.79, P<0.001) relating snow ablation period mean air temperature and peak snow water equivalent (SWE) to ablation-period NEE, we predict that earlier snowmelt and decreased SWE may cause a 45% reduction in midcentury ablation-period net carbon uptake.
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Ibañez, Raffaele Mercedes. "Vegetation drives greenhouse gas exchange, and carbon and nitrogen cycling in grassland ecosystems." Doctoral thesis, Universitat de Lleida, 2020. http://hdl.handle.net/10803/669268.
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Los pastos son el hábitat más extenso del mundo, siendo fundamentales para la mitigación del cambio climático. Sin embrago, las predicciones sobre emisiones de gases de efecto invernadero (GEI), ciclo del carbono (C) y del nitrógeno (N), todavía están marcadas por una alta incertidumbre, la cual subyace en gran medida en las interacciones entre suelo y vegetación. La presente tesis investiga cómo la vegetación influye sobre el intercambio de GEI y la dinámica del C y el N, en términos de fenología, estructura, composición y diversidad. Para este fin, se han seleccionado pastos a lo largo de un gradiente climático (desde pastos alpinos del Pirineo hasta dehesas en el suroeste de la Península Ibérica). El intercambio de GEI se determinó combinado medidas continuas (eddy covariance) y discretas (cámaras de suelo). La dinámica del C y el N, se aproximó mediante el contenido de C y N, y el ratio isotópico de 13C y 15N. Los resultados mostraron que la vegetación influyó sobre el intercambio de GEI y la dinámica del C y N a lo largo del gradiente climático y de gestión. En ambientes de montaña la fenología condicionó las interacciones entre intercambio de CO2 y vegetación, en función del estrato altitudinal. En dehesas, la estructura compuesta por árboles y pasto, condicionó las emisiones de CO2 y N2O, siendo importante la especie de árbol. El contenido de C y N, y la discriminación contra 13C y 15N incrementó bajo copa en comparación con el pasto abierto. Dicha estructura determinó la composición de grupos funcionales de plantas, éstos presentando particularidades en la adquisición y uso de C y N. Así mismo, la composición de la vegetación influyó sobre el intercambio de GEI. Las legumbres incrementaron la asimilación neta de CO2 y las emisiones de N2O; la composición de especies influyo sobre la respiración y el intercambio de N2O. La interacción entre cereales y legumbres incrementó la asimilación neta de CO2 en comparación con monocultivos de cereal, como resultado de una mayor asimilación bruta pero no mayor respiración. La inclusión de la vegetación mejoró la comprensión sobre los mecanismos que afectan al intercambio de GEI y la dinámica del C y el N.Les pastures són l’hàbitat més extens del món, essent fonamentals per a la mitigació del canvi climàtic. Tot i així, les prediccions respecte a les emissions de gasos d’efecte hivernacle (GEH) i cicle del carboni (C) i del nitrogen (N), estan encara marcades per una gran incertesa, la qual recau en bona part en les interaccions entre el sòl i la vegetació. Aquesta tesi investiga com la vegetació influeix sobre el intercanvi de GEH i la dinàmica del C i el N, en termes de fenologia, estructura, composició i diversitat. Per a aquesta finalitat, es van seleccionar pastures al llarg d’un gradient climàtic (des de prats alpins del Pirineu fins a deveses al sud-oest de la Península Ibèrica). El intercanvi de GEH es va determinar mitjançant mesures continues (eddy covariance) i discretes (cambres de sòl). La dinàmica del C i el N, es va aproximar mitjançant el contingut de C i N, i el rati isotòpic de 13C i 15N. Els resultats mostraren que la vegetació va influir sobre el intercanvi de GEH i la dinàmica del C i N al llarg del gradient climàtic i de gestió. En ambients de muntanya la fenologia va condicionar les interacciones entre el intercanvi de CO2 i la vegetació, en funció del estrat altitudinal. A les deveses l’estructura composta per arbres i pastures, va condicionar les emissions de CO2 i N2O, essent important l’espècie d’arbre. El contingut de C i N, i la discriminació contra 13C i 15N va incrementar sota copa en comparació amb la pastura oberta. Aquesta estructura va determinar la composició de grups funcionals de plantes, els quals presentaren particularitats en l’adquisició i ús de C i N. Així mateix, la composició de la vegetació influí sobre el intercanvi de GEH. Les lleguminoses incrementaren l’assimilació neta de CO2 i las emissions de N2O; la composició d’espècies va influir sobre la respiració i el intercanvi de N2O. La interacció entre cereals i lleguminoses incrementà l’assimilació neta de CO2 en comparació amb monocultius de cereal, com a resultat d’una major assimilació bruta però no major respiració. En general, la inclusió de la vegetació va millorar la comprensió sobre els mecanismes que afecten al intercanvi de GEH i la dinàmica del C i el N.
Grasslands are the most widespread habitat in the world, and play a crucial role in climate change mitigation. However, predictions about greenhouse gas (GHG) fluxes, and carbon (C) and nitrogen (N) cycling, are still marked by great uncertainty, which in good part lies on soil – vegetation interactions. Accrdingly, this thesis investigates the role of vegetation, in terms of phenology, structure and diversity, as a driver of GHG exchange, C and N cycling in grasslands along a climatic gradient (mountain grasslands and dehesa ecosystems) and under diffrent management regimes. GHG recording was done combining continuous (eddy covariance) and discrete chamber based measurements. C and N cycling was assessed using C and N content, and 13C and 15N isotope ratios as a proxy. Our results showed that vegetation influenced GHG fluxes and C and N cycling along the climatic gradient and management regimes. In mountain environments, phenology determined interactions between CO2 exchange, vegetation and environmental variables, depending on the elevation belt. In dehesa ecosystems, the tree – open grassland structure drove CO2 and N2O fluxes, with some differences among tree species. Moreover, the different plant functional types, presented marked differences in their C and N acquisition and use strategies. Legumes enhanced net CO2 uptake and N2O emissions; as well as cereal – legume interactions enhanced net CO2 uptake compared to cereal monocultures. Overall, the inclusion of vegetation structure and diversity improved the understanding of mechanisms affecting GHG exchange, and C and N cycling.
27
Bhardwaj, Anuraag K. "Seasonal variability of net carbon dioxide exchange in a headwater bog, Kenora, Ontario." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0002/MQ37094.pdf.
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Ney, Patrizia [Verfasser]. "Partitioning of carbon dioxide exchange in rapidly and slowly changing ecosystems / Patrizia Ney." Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/1200019954/34.
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Sagerfors, Jörgen. "Land-atmosphere exchange of CO₂, water and energy at a boreal minerotrophic mire /." Umeå : Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200704.pdf.
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Martin, M. J. "Models of the interactive effects of rising ozone, carbon dioxide and temperature on canopy carbon dioxide exchange and isoprene emission." Thesis, University of Essex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339238.
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Blohm, Maren Elizabeth Veatch. "Genetic and Environmental Effects on Growth, Resin and Rubber Production in Guayule (Parthenium Argentatum, Gray)." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1329%5F1%5Fm.pdf&type=application/pdf.
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Podgrajsek, Eva. "Lake Fluxes of Methane and Carbon Dioxide." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-241984.
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Methane (CH4) and carbon dioxide (CO2) are two important greenhouse gases. Recent studies have shown that lakes, although they cover a small area of the globe, can be very important natural sources of atmospheric CH4 and CO2. It is therefore important to monitor the fluxes of these gases between lakes and the atmosphere in order to understand the processes that govern the exchange. By using the eddy covariance method for lake flux studies, the resolution in time and in space of the fluxes is increased, which gives more information on the governing processes. Eddy covariance measurements at a Swedish lake revealed a diel cycle in the fluxes of both CH4 and CO2, with higher fluxes during nighttime than daytime. The high nighttime CO2 fluxes could to a large extent be explained with enhanced transfer velocities due to waterside convection. For the diel cycle of CH4 flux it was suggested that waterside convection could enhance the transfer velocity, transport CH4 rich water to the surface, as well as trigger ebullition. Simultaneous flux measurements of CH4 and CO2 have been presented using both the eddy covariance method and the floating chambers method of which the latter is the traditional measuring method for lake fluxes. For CO2 the two methods agreed well during some periods but differed considerably during others. Disagreement between the methods might be due to horizontal heterogeneity in partial pressure of CO2 in the lake. The methods agreed better for the CH4 flux measurements. However, it is clear that due to the discontinuous nature of the floating chambers, this method will likely miss important high flux events. The main conclusions of this thesis are: 1) the two gas flux methods are not directly comparable and should be seen as supplementary to each other 2) waterside convection enhances the fluxes of both CH4 and CO2 over the water-air surface. If gas flux measurements are not conducted during nighttime, potential high flux periods might be missed and estimates of the total amount of gas released from lakes to the atmosphere may be biased.
33
Pathak, Sudhir Kumar. "Treatment of Landfill leachates using anion exchange resins." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51812.
Full textAbstract:
Landfill leachates are often discharged to wastewater treatment plants (WWTPs) but their highly varied composition makes their treatment in WWTPs difficult. Landfill leachates contain bio-refractory organic matter which easily passes the biological treatment processes at WWTPs and increases the organic matter in the effluent. Leachates also interfere with the UV disinfection process at treatment plants. Another concern is the presence of large amounts of bio-refractory organic nitrogen in the leachates which makes it difficult for WWTPs to meet the tightening total nitrogen requirements.
Studies were conducted to evaluate the applicability of anion exchange resins to remove organic matter, UV quenching substance and organic nitrogen from landfill leachates. Leachate samples based on varying age and treatment methods were utilized. The anion exchange resins were found to work effectively for all studied leachates. The resins were found to remove more bio-refractory UV absorbing substances as compared to total organic carbon (TOC), suggesting that anion exchange resins could be employed for removal of UV absorbing substances. Multiple regenerations of the resin showed slight loss in the capacity to remove UV and organic carbon. Fractionation of leachate samples showed effective removal of humic acid (HA) fraction which is responsible for most of UV quenching. The resin was also found to effectively remove the bio-refractory hydrophilic (Hpi) fraction which tends to persist even after HA fraction has bio-degraded. Membrane filtration (1000 Da and 3000 Da Molecular weight cut off) in conjunction with ion exchange resins achieved better removal of organic matter and UV254 absorbing substances. In addition, this also significantly improved the performance of resins. Significant removal of organic nitrogen was also observed using anion exchange though it was less than both UV and TOC. Around 80% removal of organic nitrogen associated with bio-refractory Hpi fraction was achieved using anion exchange suggesting ion exchange as a viable alternative for removing organic nitrogen.Master of Science
34
Matthews, Ben J. H. "The rate of air-sea COâ‚‚ exchange : chemical enhancement and catalysis by marine microalgae." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323350.
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Van, Gaalen Kenneth Eric, and University of Lethbridge Faculty of Arts and Science. "Photosynthetic CO2 exchange and spectral vegetation indices of boreal mosses." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2005, 2005. http://hdl.handle.net/10133/293.
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Moss dominated ecosystems are an important part of the global terrestrial carbon cycle. Over large areas, remote sensing can be useful to provide an improved understanding of these ecosystems. Two boreal mossess (Pleurozium and Sphagnum) were assessed using remote sensing based spectral vegetation indices for estimating biochemical capacity and photosynthetic efficiency by varying net photosynthesis rate via changes in water content. In the laboratory, changes in the normalized difference vegetation index (NDVI) and chlorophyll index coincided with declining photosynthetic capacity due to desiccation. This effect was more dramatic in Sphagnum. The photochemical reflectance index (PRI) did not vary with changes in CO2 supply as anticipated, possibly due to overriding effects of changing water content. The water band index (WBI) was strongly related to water content but this relationship showed an uncoupling in the field. Bi-directional reflectance measurements indicated what WBI was sensitive to sensor, sun, and moss surface slope angles.xi, 110 leaves : ill. (some col.) ; 29 cm.
36
Teixeira, José Reinaldo Paranaíba Vilela Alves. "High spatial variability of carbon emission and gas exchange coefficient in three tropical reservoirs." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/5656.
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Reservoirs are significant sources of carbon emission to the atmosphere. However the magnitude of this emission has huge uncertainties, partly related to the methods of sampling and partly related to the unconsidered spatial-temporal variability. Here we examined the spatial variability and its drivers of partial pressure, gas exchange coefficient and diffusive flux of CO2 and CH4 in three tropical reservoirs. We observed high spatial variability in CO2 and CH4 concentration and flux within the reservoirs. Our results suggest that all reservoirs were supersaturated in both gases, even considering that some areas were CO2 sinks. A large spatial variability in k600 for CO2 and CH4, and consistently observed k600CH4 values higher than k600CO2 were also observed in all reservoirs. We could explain the high spatial variability of CO2 and CH4 by a combination of parameters such as dissolved oxygen, pH, chlorophyll, wind speed and bathymetry. Finally, we suggest a minimum sampling effort required to representatively cover a study site. Our results illustrate the first specially-resolved analysis of CH4 emissions in reservoirs, and we suggest that in large systems (area ≥ 1,000 km²) and small systems (area ≤ 100 km²), 600 and 200 measurements sites, respectively, are need for a representative dry period carbon flux estimates.
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Kross, Angela. "Characterization of the variability and controls of the carbon dioxide exchange in northern peatlands." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107759.
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Peatlands play an important role within the global carbon cycle as they account for ~20-30% of the global soil carbon, yet it is uncertain whether peatlands will continue to accumulate carbon with projected changes in climate. To improve the understanding of the carbon cycle in peatlands, it is important to know the spatial and temporal variability of the carbon dioxide (CO2) exchange and other carbon components of peatlands' carbon cycle. Studying the carbon cycle in peatlands at regional and global scales is challenging because of their remote locations and their extensive areas. Studies have used ecosystem models in combination with ground measured data and/or satellite data to obtain regional to global information about ecosystem function and production, but peatlands have not been generally included in these studies. Within this context, my research was guided by two main questions: 1) how does CO2 exchange and phenology vary in and across peatlands? 2) and how can satellite data be used to obtain estimates of CO2 exchange at larger spatial extents than the currently available field measurements? To answer these questions I used a combination of light use efficiency (LUE) models, satellite data (vegetation and phenological indices; gross primary production, GPP), and field-measured data (climate, CO2 exchange) from four functionally different northern peatlands in Canada and Europe. Analysis of the CO2 exchange data showed higher annual accumulated GPP and net ecosystem production (NEP) at the warmer peatlands. The two warmer sites had longer growing seasons and carbon uptake periods than the two colder sites. The carbon uptake period, for example was ~6 months at the warmer sites and ~3 months at the colder sites. Within each of these groups (i.e. long vs. short carbon uptake period), the sites with the higher leaf area index and with circum-neutral pH levels had higher annual GPP and NEP. Variations in interannual accumulated GPP and NEP were mainly explained by variations in monthly or seasonal precipitation. Satellite-derived vegetation indices captured the seasonal variations in GPP and NEP well, and satellite-derived phenological indices showed modest relationships with annual GPP and NEP. The LUE-based GPP from the moderate resolution imaging spectroradiometer (MODIS) performed best in capturing the seasonal variation in GPP and NEP at all sites. A more in depth analysis of LUE models identified two major challenges: 1) uncertainties in satellite input data (e.g. vegetation indices) and their relationship with ground biophysical information; and 2) fine-tuning of scalars that reduce the maximum LUE parameter (i.e. epsilon) values over time: scalars should better reflect changes in soil temperature, seasonal water availability and snow presence. These findings are important for improvement of LUE models that ultimately should lead to better characterization of regional and global peatland production. The applicability of satellite data for obtaining information on peatland function and production was showed in this study; yet, the results from the final analysis showed that it is important to examine if the available satellite data (with its predefined spatial and temporal resolutions) can provide the necessary information about the vegetation structure and function in peatlands.Les tourbières jouent un rôle important dans le cycle global du carbone car ils représentent ~20-30% du carbone global des sols, cependant avec les changements climatiques qui sont prévus il n'est pas certain qu'ils continueront à accumuler autant de carbone. Pour améliorer le compréhension du cycle de carbone dans les tourbières, il est important de connaître la variabilité spatiale et temporelle d'échange du dioxyde de carbone (CO2) et d'autres composants en carbone du cycle de carbone des tourbières. Étudier le cycle du carbone dans les tourbières à l'échelle régionale et globale est un défi en raison des sites distants et de l'étendu des grands espaces qui les caractérisent. Des études ont utilisé des modèles d'écosystème en combinaison avec des données mesurées au sol et / ou des données satellitaires pour obtenir des informations régionales et globales sur la fonction et de la production des écosystèmes, mais généralement, les tourbières n'ont pas été inclus dans ces études. Dans ce contexte, ma recherche a été guidée par deux questions principales: 1) comment l'échange de CO2 et la phénologie varient-ils dans et entre les tourbières ? 2) et comment la télédétection peut-elle être employée pour obtenir des estimations d'échange de CO2 à une échelle spatiale plus grande que les mesures disponibles obtenues sur le terrain? Pour répondre à ces questions, j'ai utilisé une combinaison de modèles basés sur l'efficacité de l'utilisation de la lumière (LUE), des données satellitaires et des données obtenues sur le terrain de quatre tourbières, fonctionnellement différentes. L'analyse des données d'échange de CO2 a montré que la GPP annuelle accumulée et la production nette d'écosystème (NEP) sont plus élevées dans les tourbières les plus chauds. Les deux sites les plus chauds avaient de plus longues saisons de croissance et de périodes d'absorption de carbone que les deux sites les plus froids. La période d'absorption de carbone par exemple, était d'environ 6 mois sur les sites les plus chauds et d'environ 3 mois sur les sites les plus froids. Dans chacun de ces groupes les sites avec l'indice de surface foliaire le plus élevé et avec les niveaux de circum-neutres de pH avaient les GPP et NEP annuelles plus élevés. Des variations en GPP et NEP inter-annuelles ont été principalement expliquées par des variations dans les précipitations mensuelles ou saisonnières. Les indices de végétation obtenues par satellite ont bien capturé les variations saisonnières de GPP et NEP, et les indices phénologiques obtenues par satellite ont montré des relations modestes avec les GPP et NEP annuelles. La GPP basé sur la LUE, obtenue à partir d'un spectroradiomètre d'imagerie à résolution modérée a obtenue de meilleurs résultat pour capturer la variation saisonnière en GPP et NEP sur tous les sites. Une analyse plus approfondie des modèles de LUE a identifié deux défis majeurs: 1) des incertitudes dans des données d'entrée de satellite (par exemple, les indices de végétation) et leur relation avec les informations biophysiques au sol, et 2) le réglage des barèmes qui réduisent la valeur du paramètre maximale de LUE (c.-à-d. epsilon) sur le temps: les barèmes devraient mieux refléter les changements dans la température du sol, la disponibilité saisonnière d'eau et la présence de neige. Ces résultats sont importants pour l'amélioration des modèles de LUE qui, en fin de compte devrait mener à une meilleure caractérisation de la production des tourbières régionales et mondiales. Cette études a montré l'applicabilité des données satellitaires pour obtenir des informations sur la fonction et la production des tourbières, cependant, les résultats de l'analyse finale ont montré qu'il est important d'examiner si les données satellitaires disponibles (avec ses résolutions spatiales et temporelles prédéfinies) peuvent fournir les informations nécessaires sur la structure et la fonction de la végétation dans les tourbières.
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Kim, Youngil. "Modeling and experimental analysis of carbon exchange from artificially flooded forest and peatland ecosystems." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104706.
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Development of hydroelectricity in recent years has stirred an international debate in relation to greenhouse gas (GHG) emissions caused by flooding, which results from the creation of hydroelectric reservoirs. The debate focuses on whether hydroelectric reservoirs are negligible global GHG sources, particularly with regards to carbon dioxide (CO₂) and methane (CH₄). Most carbon (C) exchange studies applied to hydroelectric reservoirs have been based on irregular or sporadic field measurements and, therefore, hardly address the transient nature of reservoir C flux and the heterogeneity in flux that occurs across different types of ecosystems inundated with water. In this context, ecosystem modeling and laboratory experiments can improve our understanding of C exchange that takes place in flooded terrestrial ecosystems as a consequence of hydroelectric development. The aim of this research was to examine C exchange variation in boreal forest and peatland ecosystems prior to and after flooding as well as to project boreal ecosystem C exchange for the duration of the inundation period. The primary study area was the Eastmain-1 reservoir located in northern Quebec where impoundment was completed in 2006. For this research, a reservoir C model (FF-DNDC) was developed by modifying Forest-DNDC, a process-based biogeochemical model utilized for forest and wetland ecosystems. FF-DNDC was designed to replicate C processes that take place in submerged soil and the water column. It is used to simulate CO₂ flux in flooded boreal forest and peatland ecosystems. The reliability of the Forest-DNDC simulation in relation to CO₂ flux in black spruce forest and peatland ecosystems was tested before modifications to the software took place. This test showed that Forest-DNDC reasonably simulated CO₂ flux and, as a result, supported the application of the model to simulate C dynamic changes after flooding occurs. Short-term incubation experiments using boreal soil and vegetation samples revealed that flooding decreased rates of CO₂ production but increased rates of dissolved C production. The experiments quantified changes that occurred in C mineralization rates prior to and after flooding, which determined soil decomposition parameters under flooded conditions that were then applied to FF-DNDC. The Eastmain-1 reservoir flooded ecosystem simulations detected CO2 emissions from the water surface, and, hence, the direction in CO₂ flux changed (from uptake to release) in comparison to flux that occurred in natural forest and peatland ecosystems. Simulated CO₂ flux for both the flooded forest and peatland ecosystems decreased with the duration of inundation, and the forest ecosystem showed larger CO₂ flux than the peatland ecosystem in the first decade after flooding was initiated. The trend of larger flux in the forest ecosystem was reversed after the first decade. Modeling and experimental results from this study emphasize the importance of spatial and temporal variation of C exchange in newly flooded boreal landscapes.La production d'hydroelectricite est devenue le sujet d'un debat international ces dernieres annees en raison de l'emission des gaz a effet de serre (GES) qui resulte de l'inondation de la zone en amont d'un barrage hydroelectrique lors de la creation du reservoir. Le debat vise a determiner si les reservoirs des barrages hydroelectriques sont des sources negligeables de GES, plus particulierement en relation avec le dioxyde de carbone (CO₂) et le methane (CH₄). La plupart des etudes sur les echanges carboniques dans les reservoirs hydroelectriques furent basees sur des mesures irregulieres ou sporadiques prises sur terrain, et consequemment elles n'examinent pas en profondeur les tendances transitoires des flux de carbone (C) des reservoirs, ni l'heterogeneite des flux a travers les differents types d'ecosystemes inondes. Ceci etant dit, la modelisation des ecosystemes ainsi que les experimentations de laboratoire pourront ameliorer notre comprehension quant a l'inondation des echanges carboniques des ecosystemes terrestres qui surviennent suite au developpement hydroelectrique. Ma recherche vise a examiner l'alteration des echanges carboniques dans les forets boreales et les tourbieres avant et apres leur inondation, ainsi qu'a prevoir les echanges carboniques des ecosystemes boreals pendant la duree de l'inondation. La region sous etude fut le reservoir Eastmain-1 au nord du Quebec, dont la creation du reservoir fut terminee en 2006. Pour cette recherche, j'ai cree un modele sur le C des reservoirs (FF-DNDC) en modifiant Forest-DNDC, un modele de processus biogeochimique destine aux forets et les milieux humides. FF-DNDC a ete concu pour simuler les processus carboniques dans les sols inondes ainsi que dans la colonne d'eau, et a ete utilise pour predire les flux de CO₂ dans les forets boreales inondees et les tourbieres. Avant la modification du logiciel, j'ai teste la fiabilite avec laquelle Forest-DNDC pourra simuler les flux de CO₂ dans les forets d'epinette noire et les tourbieres. Ce test a demontre que Forest-DNDC peut simuler les flux de CO₂ avec une grande precision, et peut donc etre utilise pour evaluer les dynamiques de C suivant leur inondation. Des experiences d'incubation a court terme utilisant des sols boreals et de la vegetation ont revele que l'inondation diminue les taux de production de CO₂, tout en augmentant les taux de production de C dissous. Les experiences ont quantifie les changements dans les taux de mineralisation du C avant et apres l'inondation, afin de determiner les parametres de decomposition des sols dans les conditions inondees; ces parametres furent ensuite utilises dans FF-DNDC. Les simulations des ecosystemes inondes dans le reservoir Eastmain-1 ont indique qu'il y avait une emission de CO₂ des surfaces d'eau, et donc que la direction des flux de CO₂ a change (allant d'une absorption a une emission par l'ecosysteme) compare aux flux chez les forets et les tourbieres naturelles. Les flux de CO₂ simules dans la foret inondee et la tourbiere diminuaient pendant la duree de l'inondation, et la foret avait des flux de CO₂ superieurs a ceux de la tourbiere pendant la premiere decennie de l'inondation. Par la suite, ce contraste s'est inverse. Les resultats de mes modelisations et experiences mettent en evidence l'importance des variations spatiales et temporelles des echanges carboniques dans les paysages boreals nouvellement inondes.
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Shaheen, Robina. "Investigation of the oxygen isotope exchange between carbon dioxide and O3 via O(1D)." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB12168036.
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Butterworth, Brian J. "Air-sea carbon dioxide exchange in the Southern Ocean and Antarctic Sea ice zone." Thesis, State University of New York at Albany, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10149297.
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The Southern Ocean is an important part of the global carbon cycle, responsible for roughly half of the carbon dioxide (CO2) absorbed by the global ocean. The air-sea CO2 flux (Fc) can be expressed as the product of the water-air CO2 partial pressure difference (ΔpCO2) and the gas transfer velocity ( k), an exchange coefficient which represents the efficiency of gas exchange. Generally, Fc is negative (a sink) throughout the Southern Ocean and Antarctic sea ice zone (SIZ), but uncertainty in k has made it difficult to develop an accurate regional carbon budget. Constraining the functional dependence of k on wind speed in open water environments, and quantifying the effect of sea ice on k, will reduce uncertainty in the estimated contribution of the Southern Ocean and Antarctic SIZ to the global carbon cycle.
To investigate Fc in the Southern Ocean, a ruggedized, unattended, closed-path eddy covariance (EC) system was deployed on the Antarctic research vessel Nathaniel B. Palmer for nine cruises during 18 months from January 2013 to June 2014 in the Southern Ocean and coastal Antarctica. The methods are described and results are shown for two cruises chosen for their latitudinal range, inclusion of open water and sea ice cover, and large ΔpCO2. The results indicated that ship-based unattended EC measurements in high latitudes are feasible, and recommendations for deployments in such environments were provided.
Measurements of Fc and ΔpCO2 were used to compute k. The open water data showed a quadratic relationship between k (cm hr–1) and the neutral 10-m wind speed (U10n, m s –1), k=0.245 U10n 2+1.3, in close agreement with tracer-based results and much lower than previous EC studies. In the SIZ, it was found that k decreased in proportion to sea ice cover. This contrasted findings of enhanced Fc in the SIZ by previous open-path EC campaigns. Using the NBP results a net annual Southern Ocean (ocean south of 30°S) carbon flux of –1.1 PgC yr–1 was calculated.
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Payne, Martin William. "Investigation of the reactivity of [HM?(CO)??]? (M = Ru, Os) clusters : kinetics of ¹³CO exchange, effects of ion pairing, and the relationship between the ¹³CO exchange and the catalysis of the water-gas shift reaction /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487332636477575.
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SOUZA, LETICIA L. de. "Uso da voltametria cíclica e da espectroscopia de impedância eletroquímica na determinação da área superficial ativa de eletrodos modificados à base de carbono." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10040.
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Made available in DSpace on 2014-10-09T12:34:05Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:59:48Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Berry, Stephanie C. Carleton University Dissertation Biology. "The influence of vegetation and soil carbon dioxide exchange on the concentration and isotopic composition of atmospheric carbon dioxide within plant canopies." Ottawa, 1994.
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Chan, Wai-hung, and 陳偉雄. "Fabrication of aligned carbon nanotubes layer and interfacing with Nafion membrane for potential application in fuel cells." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B44518559.
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Morén, Ann-Sofie. "Carbon dioxide and water exchange in a boreal forest in relation to weather and season /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5620-7.pdf.
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Duggan, Michael J. "The use of isotopic oxygen exchange to investigate carbon monoxide oxidation over supported gold catalysts." Thesis, Nottingham Trent University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271214.
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Castanheira, Luis Filipe Rodrigues. "Corrosion of high surface area carbon supports used in proton-exchange membrane fuel cell electrodes." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI084/document.
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Cette thèse est consacrée à l’étude des mécanismes de dégradation de noirs de carbone de forte surface spécifique (HSAC) utilisés comme supports d’électrocatalyseurs dans une pile à combustible à membrane échangeuse de protons (PEMFC). Nous avons montré que le mécanisme et les cinétiques de la corrosion électrochimique du carbone (COR) sont influencés par la présence d’ionomère Nafion®, la limite supérieure de potentiel électrochimique, la nature et le nombre de caractérisations intermédiaires présentes dans des tests de dégradation accélérés. En utilisant la spectroscopie Raman,il apparaît que la COR est sensible à la structure cristallographique des HSAC et procède plus rapidement sur les domaines désordonnés (carbone amorphe, cristallites de graphite présentant des défauts). Le taux de recouvrement en espèces oxygénées évalué par spectroscopie de photoélectrons X a été comparé à celui trouvé en intégrant l’intensité du pic quinone/hydroquinone (Q/HQ) envol tampérométrie cyclique. Finalement, une comparaison avec des matériaux carbonés ayant fonctionné pendant 12860 heures en PEMFC confirme nos principaux résultats et permet d’élaborer des stratégies pour atténuer les conséquences de la CORThis thesis investigates the degradation mechanism of high surfacearea carbon (HSAC) supports used in proton-exchange membrane fuel cell (PEMFC) electrodes. The structural and the chemical properties of different HSAC supports were established. The effectof the Nafion® ionomer used as a proton conductor, the gas atmosphere, the upper potential limit and the intermediate electrochemical characterizations used to monitor the changes ofthe electrochemical surface area during accelerated stress tests(ASTs) were investigated. The long-term physical and chemical changes of Pt/HSAC electrocatalysts were investigated insimulated PEMFC operating conditions. Using Raman spectroscopy, we showed that the COR is strongly structure sensitive and proceeds more rapidly on disordered domains of the HSAC (amorphous carbon and defective graphite crystallites) thanon graphitic domains. The coverage with carbon surface oxides was investigated with X-ray photoelectron spectroscopy and bridged tothe intensity of the quinone/hydroquinone (Q/HQ) peak monitored by cyclic voltammetry. Finally, the analyses realized on membrane electrode assemblies operated for 12,860h disclosed a perfect agreement between model and real PEMFC operating conditions, and confirmed the structural dependency of the COR kinetics
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Morrison, Ross David. "Land/atmosphere carbon dioxide exchange at semi-natural and regenerating peatlands in East Anglia, UK." Thesis, University of Leicester, 2013. http://hdl.handle.net/2381/27972.
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This thesis presents the first direct flux measurements of land/atmosphere carbon dioxide (CO[subscript 2]) exchange at managed lowland peatlands in the East Anglian Fens, UK. The dynamics and magnitude of land/atmosphere CO[subscript 2] exchange were quantified at semi-natural and regenerating ex-arable fens located at the Wicken Fen Nature Reserve in Cambridgeshire. Eddy covariance measurements were made at the semi-natural fen throughout two thermally and hydrologically dissimilar periods during 2009 and 2010, and at the regenerating former-arable fen over the complete annual cycle of 2010. The study sites were characterised by strong seasonal variation in CO[subscript 2] exchange. The semi-natural fen was a net source of 85.47±25.78 g CO[subscript 2]-C m[superscript -2] between 20th March and 31st December 2009, and a small net sink of -22.66±18.85 g CO[subscript 2]-C m[superscript -2] for the same period of 2010. Photosynthesis and ecosystem respiration were both higher during warm conditions of 2009 compared to 2010, but enhanced rates of ecosystem production were outweighed by large CO[subscript 2] losses during warm and dry conditions in autumn. The large interannual variability in CO[subscript 2] exchange illustrates the sensitivity of semi-natural fens to climatic variability and change, and highlights the need to maintain high water levels to prevent large losses of soil carbon to the atmosphere as CO[subscript 2]. The regenerating fen functioned as a small net source of 21.24±17.11 g CO[subscript 2]-C m[superscript -2] yr[superscript -1]. On the basis of values currently used to represent CO[subscript 2] losses from arable fens, the annual CO[subscript 2] balance for the ex-arable fen in 2010 indicates the net CO[subscript 2] benefit of fenland rehabilitation was an avoided loss of -87.7±17.11g CO[subscript 2]-C m[superscript -2] yr[superscript -1]. The results from the regenerating site imply that a more adaptive water management strategy will be needed if the environmental conditions required for peat formation and net carbon capture are to be restored.
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Ghannoum, Oula, of Western Sydney Hawkesbury University, Faculty of Agriculture and Horticulture, and School of Horticulture. "Responses of C3 and C4 Panicum grasses to CO2 enrichment." THESIS_FAH_HOR_Ghannoum_O.xml, 1997. http://handle.uws.edu.au:8081/1959.7/139.
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This project aims at investigating the effect of CO2 enrichment on the growth and gas exchange of C3, C3-C4 and C4 Panicum grasses. Potted plants were grown in soil under well watered conditions, in artificially lit environmentally controlled cabinets or naturally lit greenhouses at varying levels of CO2 enrichment. CO2 enrichment enhanced the dry weight of C3 and C4 Panicum species under optimal light and N supplies, but had no effect on the total leaf N or TNC concentrations. The high-CO2 induced photosynthetic reaction in the C3 species was accompanied by a reduced Rubisco concentration and was related to the conservation of the relative growth rate of the plant. Elevated CO2 had no effect on the photosynthetic capacity of the C4 species, but enhanced its CO2 assimilation rates under high light and N supplies. The effect of elevated CO2 on the leaf and stem anatomy reflected increased carbon supply at high CO2 in the C3 grass, and reduced transpiratory demand at high CO2 in C4 grasses. Consequently, it is clear that both C3 and C4 grasses are likely to be more productive under rising atmospheric CO2 concentrations.Doctor of Philosophy (PhD)
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Cambaliza, Maria Obiminda L. "Measurement of forest ecosystem-atmosphere exchange of 8¹³C-CO₂ using Fourier transform infrared spectroscopy and disjunct eddy covariance." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Spring2010/m_cambaliza_121709.pdf.
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Thesis (Ph. D.)--Washington State University, May 2010.Title from PDF title page (viewed on June 10, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references.