Dissertationen: „Carbon sinks or sources“

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Gudasz, Cristian. „Boreal Lake Sediments as Sources and Sinks of Carbon“. Doctoral thesis, Uppsala universitet, Limnologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-150709.

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Inland waters process large amounts of organic carbon, contributing to CO2 and CH4 emissions, as well as storing organic carbon (OC) over geological timescales. Recently, it has been shown that the magnitude of these processes is of global significance. It is therefore important to understand what regulates OC cycling in inland waters and how is that affected by climate change. This thesis investigates the constraints on microbial processing of sediment OC, as a key factor of the carbon cycling in boreal lakes. Sediment bacterial metabolism was primarily controlled by temperature but also regulated by OC quality/origin. Temperature sensitivity of sediment OC mineralization was similar in contrasting lakes and over long-term. Allochthonous OC had a strong constraining effect on sediment bacterial metabolism and biomass, with increasingly allochthonous sediments supporting decreasing bacterial metabolism and biomass. The bacterial biomass followed the same pattern as bacterial activity and was largely regulated by similar factors. The rapid turnover of bacterial biomass as well as the positive correlation between sediment mineralization and bacterial biomass suggest a limited effect of bacterial grazing. Regardless of the OC source, the sediment microbial community was more similar within season than within lakes. A comparison of data from numerous soils as well as sediments on the temperature response of OC mineralization showed higher temperature sensitivity of the sediment mineralization. Furthermore, the low rates of areal OC mineralization in sediments compared to soils suggest that lakes sediments are hotspots of OC sequestration. Increased sediment mineralization due to increase in temperature in epilimnetic sediments can significantly reduce OC burial in boreal lakes. An increase of temperature, as predicted for Northern latitudes, under different climate warming scenarios by the end of the twenty-first century, resulted in 4–27% decrease in lake sediment OC burial for the entire boreal zone.

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Mayorga, Emilio. „Isotopic constraints on sources and cycling of riverine dissolved inorganic carbon in the Amazon Basin /“. Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/10977.

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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.

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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.

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Richmond, Nicole L. „THE CARBON BUDGET OF A SHALLOW, TROPICAL AQUIFER: SOURCES, SINKS, AND PROCESSES“. Oxford, Ohio : Miami University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1070212062.

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Thesis (M.S.)--Miami University, Dept. of Geology, 2003.
Title from first page of PDF document. Document formatted into pages; contains vii, 127 p. : ill. Includes bibliographical references (p. 108-113).

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Dawson, Julian J. C. „The controls on concentrations and fluxes of gaseous, dissolved and particulate carbon in upland peat dominated catchments“. Thesis, University of Aberdeen, 2000. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU125517.

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A programme of field sampling was undertaken to quantify total carbon fluxes (DOC, POC, HCO3, free CO2 and CH4) from peatland catchments in Glen Dye, NE Scotland and Plynlimon, Mid-Wales. This was integrated with temporal and spatial sampling to investigate controls on contrasting concentrations and fluxes and to determine carbon sources or sinks within the stream system. Microcosms containing radiolabelled ( 14C) biofilms were also used to investigate removal of DOC from streamwater. Carbon fluxes from acidic peatlands were dominated by DOC (115-215 kg C ha-1 yr-1) and POC (8.15-97.0 kg ha -1 yr-1). In the majority of headwaters studied, DIC was exported as free CO2 (2.62-8.49 kg ha-1 yr -1). Methane-C fluxes at the outlets of catchments were <0.01 kg ha-1 yr-1. Small-scale (diurnal) temporal variations in free CO2, HCO3- and pH at the NE Scotland catchments were small compared to more productive systems; DOC showed no diurnal fluctuations. In addition, diurnal patterns were masked by marked variations in discharge. Small-scale downstream spatial changes in Brocky Burn, NE Scotland and the Upper Hafren, Mid-Wales showed that variation in climate, in particular precipitation, was also a major controlling factor on concentrations and fluxes of the different forms of carbon. However, the actual amount of carbon stored within the soils acted as an initial control on the potential DOC load within the streamwater. A peatland stream continuum linked to terrestrial carbon cycling is presented. Initially terrestrial inputs of DOC, POC, free CO2 and CH 4 dominated the upper headwaters. The soil-stream linkage was progressively reduced downstream due to autochthonous and atmospheric factors. A critical area in the peatland stream continuum occurred approximately 1 km downstream from the gaseous carbon-rich peats.

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Stephen, Amy Louise. „Carbon sources and sinks within the Oman-UAE ophiolite : implications for natural atmospheric CO2 sequestration rates“. Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/37249.

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Hyperalkaline (pH >11) spring waters across the Oman-UAE ophiolite have precipitated large-scale surface and subsurface freshwater carbonate deposits within and on mantle-sequence peridotites. Ten carbonate lithofacies have been identified that display a common stratigraphy across the region, with some on-going deposition. Alternating wet and arid climate periods, consistent with previous Quaternary climate data for Oman and the UAE, can be inferred from the morphologies and stratigraphy of carbonate lithofacies. Carbon and oxygen stable isotope ratios for individual lithofacies are consistent across the ophiolite, indicating uniform formation processes throughout the region. Modern carbonates actively precipitate via the drawdown of atmospheric CO2 into hyperalkaline groundwaters, indicated by very negative δ13C values (≈ –25‰) and δ18O (≈ –18‰) caused by kinetic fractionation. In contrast, ancient travertines display a much wider range in δ13C and δ18O, reflecting mixing of several C and O sources including atmospheric CO2, dissolved limestone CO32– and soil DIC. Radiocarbon data for ancient travertines show a series of stratigraphically impossible 14C “ages” which are interpreted to be due to the incorporation of a proportion of 14C-dead carbon. The sources of 14C-dead carbon are a mixture of dissolved limestone CO32–, soil DIC and the re-working of older carbonate deposits. The proportion of carbon from different sources must be taken into account when calculating sequestration rates of atmospheric CO2 into carbonates. The incorporation of 14C-dead carbon into carbonate lithofacies leads to a systematic offset in conventional radiocarbon ages towards older ages. Use of offset, older ages will cause underestimation of the rate of carbon sequestration, whilst the presence of 14C-dead carbon will cause overestimation of the volume of atmospheric carbon being stored. Age offsets in carbonates mean that sequestration rates taking into account all carbon in the system, e.g. from atmospheric or limestone CO32–, will be higher than previously thought.

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Gathany, Mark A. „Sources of variation in ecosystem carbon pools : a comparison of adjacent old- and second-growth forests /“. Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1102537971.

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Karlsson, Emma. „Compositional clues to sources and sinks of terrestrial organic matter transported to the Eurasian Arctic shelf“. Doctoral thesis, Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116876.

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The amount of organic carbon (OC) present in Siberian Arctic permafrost soils is estimated at twice the amount of carbon currently in the atmosphere. The shelf seas of the Arctic Ocean receive large amounts of this terrestrial OC from Eurasian Arctic rivers and from coastal erosion. Degradation of this land-derived material in the sea would result in the production of dissolved carbon dioxide and may then add to the atmospheric carbon dioxide reservoir. Observations from the Siberian Arctic suggest that transfer of carbon from land to the marine environment is accelerating. However, it is not clear how much of the transported OC is degraded and oxidized, nor how much is removed from the active carbon cycle by burial in marine sediment. Using bulk geochemical parameters, total OC, d13C and D14C isotope composition, and specific molecular markers of plant wax lipids and lignin phenols, the abundance and composition of OC was determined in both dissolved and particulate carrier phases: the colloidal OC (COC; part of the dissolved OC), particulate OC (POC), and sedimentary OC (SOC). Statistical modelling was used to quantify the relative contribution of OC sources to these phases. Terrestrial OC is derived from the seasonally thawing top layer of permafrost soil (topsoil OC) and frozen OC derived from beneath the active layer eroded at the coast, commonly identified as yedoma ice complex deposit OC (yedoma ICD-OC). These carbon pools are transported differently in the aquatic conduits. Topsoil OC was found in young DOC and POC, in the river water, and the shelf water column, suggesting long-distance transport of this fraction. The yedoma ICD-OC was found as old particulate OC that settles out rapidly to the underlying sediment and is laterally transported across the shelf, likely dispersed by bottom nepheloid layer transport or via ice rafting. These two modes of OC transport resulted in different degradation states of topsoil OC and yedoma ICD-OC. Terrestrial CuO oxidation derived biomarkers indicated a highly degraded component in the COC. In contrast, the terrestrial component of the SOC was much less degraded. In line with earlier suggestions the mineral component in yedoma ICD functions as weight and surface protection of the associated OC, which led to burial in the sediment, and limited OC degradation. The degradability of the terrestrial OC in shelf sediment was also addressed in direct incubation studies. Molecular markers indicate marine OC (from primary production) was more readily degraded than terrestrial OC. Degradation was also faster in sediment from the East Siberian Sea, where the marine contribution was higher compared to the Laptev Sea. Although terrestrial carbon in the sediment was degraded slower, the terrestrial component also contributed to carbon dioxide formation in the incubations of marine sediment. These results contribute to our understanding of the marine fate of land-derived OC from the Siberian Arctic. The mobilization of topsoil OC is expected to grow in magnitude with climate warming and associated active layer deepening. This translocated topsoil OC component was found to be highly degraded, which suggests degradation during transport and a possible contribution to atmospheric carbon dioxide. Similarly, the yedoma ICD-OC (and or old mineral soil carbon) may become a stronger source with accelerated warming, but slow degradation may limit its impact on active carbon cycling in the Siberian Shelf Seas.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

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Bairam, Emna. „Etude des processus écophysiologiques caractérisant la distribution du carbone entre les sources et les puits au sein de la charpentière du pommier. Eléments pour un modèle fonction-structure“. Thesis, Rennes, Agrocampus Ouest, 2017. http://www.theses.fr/2017NSARC129/document.

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La synthèse et le transport du carbone chez le pommier repose sur un ensemble de mécanismes complexes et imbriqués dépendants de facteurs endogènes et exogènes. Uneapproche combinant une caractérisation écophysiologique et l’utilisation d’un modèle structure-fonction de la plante (Functional-Structural Plant Model, FSPM) présente un moyenintéressant pour ce champ de recherche dans la mesure où un modèle structure-fonction permet d’intégrer la topologie et la géométrie de la plante et de ses différents organes à l’ensemble des facteurs impliqués dans l’assimilation et le transport du carbone et de l’eau. Le travail présenté ici a contribué à la compréhension des relations sources-puits mais égalementà l’élaboration d’un modèle FSPM à plusieurs niveaux. Premièrement, le développement de modèles de prédiction de l’architecture des différentes pousses du pommier à partir de variables simples apporte un moyen novateur pour simplifier la simulation de l’architecturedes branches mais égalementpour quantifi er de façon robuste la surface foliaire. Deuxièmement,l’établissement d’un réseau de corrélations entrevariables morphométriques des différents organes issus dubourgeon mixte met en évidence les organes les plus connectésà l’échelle du spur. Enfi n, une étude des relations sourcespuitsà l’échelle de la branche a permis, d’une part, une caractérisationde la régulation de la photosynthèse nette desfeuilles en réponse à des changements dans le ratio sources/puits mais aussi en fonction des types de feuilles et, d’autrepart, à mettre la lumière sur l’infl
The synthesis and the transport of carbon in apple are basedon a whole host of complex and interlaced mechanisms thatdepend on endogenous and exogenous factors. An approachthat combines the ecophysiological characterisation with theuse of a Functional-Structural Plant Model (FSPM) representsan interesting method in this fi eld of research, inasmuch assuch an FSPM allows integrating the topology and the geometryof the plant and its constituting organs with the entiretyof factors involved in assimilation as well as water andcarbon transport. The present study has contributed to thebetter understanding of the source-sink relations characterizingthis system but also to the elaboration of a multi-scaledFSPM. First, the development of models for the prediction ofthe architecture of different shoot types in apple from simplevariables provides a novel way to simplify the simulationof theinitial structure of branches but also to quantify leaf area in arobust manner. Second, the creation of a network of correlationsamong morphometric variables of the different organsformed by the mixed bud of apple clearly shows the functionalrelations among the spur organs. In the end, the study ofsource-sink relations at the branch scale has allowed, on theone hand, to characterize the regulation of net photosynthesisas a function of a changed source/sink ratio but also asa function of leaf type and, on the other hand, to shed somelight on the infl uence that the competition among fruits hason increasing sink strength and thus regulating the leaf

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Archbold, Brad. „Using algae to capture CO₂ and as a feedstock for biofuel“. Online pdf file accessible through the World Wide Web, 2007. http://archives.evergreen.edu/masterstheses/Accession86-10MES/Archbold_%20B%20MESThesis%202007.pdf.

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Wang, Yuting [Verfasser], Mathias [Akademischer Betreuer] Palm, Justus [Gutachter] Notholt und Annette [Gutachter] Ladstätter-WeißEnmayer. „Using solar FTIR spectrometry to investigate the sources and sinks of carbonyl sulfide and its application to the carbon cycle / Yuting Wang ; Gutachter: Justus Notholt, Annette Ladstätter-Weißenmayer ; Betreuer: Mathias Palm“. Bremen : Staats- und Universitätsbibliothek Bremen, 2016. http://d-nb.info/1120555353/34.

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Girard, Léo. „Étangs piscicoles et services écosystémiques : Relations entre pratiques de gestion, maintien de la biodiversité et stockage de carbone“. Electronic Thesis or Diss., Paris, AgroParisTech, 2024. http://www.theses.fr/2024AGPT0008.

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L'Europe renferme de nombreux paysages d'étangs, pour beaucoup avec une origine pouvant remonter au Moyen-âge et une vocation historique de production piscicole. Ces milieux, malgré qu'ils soient anthropisés, sont connus pour leur capacité à présenter une biodiversité importante, avec des espèces rares, voir endémiques ou menacées. Avec l'abandon de la pisciculture, combiné à d'autres menaces comme le changement climatique, un nombre significatif de ces étangs ont disparus au cours des dernières décennies. Jusqu'à récemment, et ce malgré le rôle important qu'ils peuvent jouer, ces petits plans d'eau ont de plus été négligés en Recherche, mais également par les politiques publiques.Dans ce travail de thèse nous nous sommes intéressés aux effets de différentes pratiques de gestion piscicoles sur certains services écosystémiques rendus par les étangs piscicoles. Dans un premier temps, nous avons analysé la pratique de l'assec et ses impacts à la fois sur la biodiversité et sur la productivité en poissons. Dans un second temps, nous avons exploré les impacts de différentes gestions de la densité piscicole sur les caractéristiques des communautés de macrophytes. Et enfin, nous avons étudié les étangs piscicoles comme potentiels puits ou sources de carbone, et les effets des pratiques de gestion sur ces bilans carbone.Pour compléter les connaissances scientifiques sur ces thématiques, nous avons capitalisé sur des données historiques collectées en Dombes (Ain, France) depuis 2007, mais également sur des données collectées dans le cadre du projet européen PONDERFUL, entre 2021 et 2022, en Dombes et dans le Midden-Limburg (Belgique). Nous avons analysé à la fois des données sur la physico-chimie de l'eau et des sédiments, ainsi que des données de biodiversité (macrophytes, phytoplancton et macroinvertébrés), de stockage et d'émissions de carbone, ainsi que sur les pratiques de gestion piscicoles (distance au dernier assec, empoissonnage, fertilisation).Nos résultats démontrent que l'assec constitue une pratique agroécologique majeure pour la pisciculture extensive en étang. Cet assèchement volontaire favorise la recolonisation des macrophytes ainsi que leur diversité lors de la remise en eau. La deuxième année en eau est caractérisée par un “état instable” d'équilibre entre les deux producteurs primaires. Cet état apparait comme étant favorable à la fois à la biodiversité, à la production mais également au stockage du carbone. L'intensification de la production, à travers une augmentation des densités piscicoles, a néanmoins des effets négatifs sur la richesse spécifique des macrophytes. Elle impacte également la structure des communautés. Les étangs piscicoles possèdent des sous-ensembles d'espèces, nichés dans les communautés plus riches des étangs gérés sans poissons. Nous avons également pu montrer une très forte variabilité sur les bilans carbone réalisés sur 20 étangs piscicoles. En moyenne, les étangs monitorés apparaissent comme étant plutôt des puits de carbone, à hauteur d'environ 4 tonnes de CO2 équivalent stocké par hectare et sur 6 mois. La phase d'assec est quant à elle caractérisée par des émissions de gaz à effet de serre importantes.Tous ces éléments permettent de confirmer que les étangs piscicoles, associés à des pratiques extensives, peuvent fournir de nombreux services écosystémiques. La production piscicole n'est pas antinomique de la conservation de la biodiversité. La pérennité de ces milieux dans les paysages européens, et des services fournis, passe par le maintien de ces pratiques de gestion. Même si concilier les services d'approvisionnement et de support semble possible, à l'avenir, une hiérarchisation des services souhaités sera nécessaire, notamment au regard des effets inverses que peuvent avoir certaines pratiques de gestion
Europe is home to a large number of “pond landscapes”, many with origins dating back to the Middle Ages and a historic vocation for fish farming. Despite their man-made nature, these environments are known for their capacity to harbor significant biodiversity, with rare, even endemic or endangered species. With the abandonment of fish farming, combined with other threats such as climate change, a significant number of these ponds have disappeared in recent decades. Until recently, and despite the important role they can play, these small water bodies have been neglected in research, but also in public policies.In this PhD thesis work, we looked at the effects of different fish farming management practices on ecosystem services provided by fish ponds. First, we analyzed the practice of drying-out ponds and its impact on both biodiversity and fish yields. Secondly, we explored the impacts of different fish density management on macrophyte community characteristics. And finally, we studied fish ponds as potential carbon sinks or sources, and the effects of management practices on these carbon balances.To contribute to the scientific knowledge on these topics, we capitalized on historical data collected in the Dombes region (Ain, France) since 2007, but also on data collected as part of the European PONDERFUL project, between 2021 and 2022, in Dombes and Midden-Limburg (Belgium). We analyzed data on water and sediment physico-chemistry, as well as biodiversity (macrophytes, phytoplankton and macroinvertebrates), carbon storage and emissions, and fish farming management practices (time since the last dry year, fish stocking, fertilization).Our results show that drying-out is a major agroecological practice for extensive pond fish farming. This voluntary draining facilitates the recolonization of macrophytes and their diversity when the pond is re-watered. The second year in water is characterized by an "unstable state" of equilibrium between the two primary producers. This state appears to be favorable to biodiversity, production and carbon storage. Intensification of production, through increased fish densities, nevertheless has negative effects on macrophyte species richness. It also impacts community structure. Ponds used for fish farming have subsets of species that nest in the richer communities of ponds managed without fish. We were also able to show a very high degree of variability in the carbon balances of 20 fish ponds. On average, monitored ponds appear to be carbon sinks, with around 4 tonnes of CO2 equivalent stored per hectare over 6 months. The dry year, on the other hand, is characterized by high greenhouse gas emissions.All these elements confirm that fish ponds, combined with extensive practices, can provide numerous ecosystem services. Fish production is not incompatible with biodiversity conservation. The sustainability of these environments in European landscapes, and of the ecosystem services they provide, depends on the maintenance of these management practices. Even if it seems possible to reconcile provisioning and support services, in the future it will be necessary to establish a hierarchy of desired services, particularly in view of the inverse effects that certain management practices may have

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Rosner, Hillary. „Tropical rainforests: Carbon sink or carbon source?“ Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1439430.

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Moreau, Sébastien D. V. „Effets combinés du réchauffement climatique et du rayonnement UVB sur la composition et le métabolisme de la communauté microbienne marine dans l'ouest de la Péninsule Antarctique : impact potentiel sur le cycle du carbone“. Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20028.

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Le réchauffement régional de l'ouest de la Péninsule Antarctique (WAP) combiné à la diminution attendue de glace de mer et à l'apparition printanière du trou d'ozone pourrait modifier la composition et la structure de la communauté microbienne. De plus, ces variations environnementales pourraient modifier le potentiel de la WAP en tant que puits de CO2. Dans ce contexte, cette thèse visait à évaluer les effets combinés du changement climatique sur la production primaire et sur la composition et la structure de la communauté microbienne de la WAP. Cette thèse visait également à évaluer le rôle de la structure, de la composition, de la production primaire et de la respiration de la communauté microbienne sur les échanges de CO2 entre l'atmosphère et l'océan. Cette étude a premièrement permis de décrire les variations de l'étendue de glace de mer, de l'épaisseur de la couche d'ozone et de la température de surface de l'eau dans la WAP au cours des 30 dernières années (1972-2007) et notamment d'observer le retrait de plus en plus précoce de la glace de mer en relation avec le réchauffement des eaux de la WAP. L'évolution de ces paramètres environnementaux offre une nouvelle fenêtre temporelle de production primaire. Ainsi, cette étude a permis de montrer que la production primaire annuelle a augmenté de 1997 à 2007, et ceci, en relation avec l'anomalie de glace de l'hiver précédent. En effet, la production primaire journalière était négativement et positivement corrélée avec, respectivement, l'étendue de glace de mer et la température de l'eau de septembre à novembre et de février à mars, suggérant que le réchauffement régional de la WAP favorise plus de production primaire durant le printemps et l'automne. En revanche, le retrait précoce de la glace de mer en coïncidence avec l'apparition printanière du trou d'ozone a provoqué l'augmentation de la photoinhibition au printemps (avec 11,6 ± 2,8 % de la production primaire journalière en moyenne). En conséquence, le changement climatique régional de la WAP a, à la fois, un effet positif et un effet négatif sur la production primaire. Cette étude a également permis de décrire la dynamique de la communauté microbienne marine dans l'archipel de Melchior (dans la WAP) de l'automne au printemps 2006. En raison des conditions environnementales extrêmes, l'abondance et la biomasse de la communauté microbienne étaient faibles durant l'automne et l'hiver et dominées par les petites cellules (< 2 µm) et donc par un réseau trophique microbien. En effet, la biomasse phytoplanctonique était faible durant l'automne et l'hiver (avec une concentration moyenne en chlorophylle a, Chl-a, de 0,3 et 0,13 µg l-1, respectivement). La biomasse phytoplanctonique a augmenté au printemps (avec un maximum de Chl-a de 1,13 µg l-1), mais, en dépit des conditions de croissance favorables, est restée faible et le phytoplancton était toujours dominé par de petites cellules (2-20 µm) et donc par le réseau trophique microbien ou multivore. De plus, la disparition précoce de glace de mer durant le printemps 2006 a exposé les eaux de la WAP à de fortes radiations ultraviolettes B (RUVB, 280-320 nm), qui ont eu un effet négatif sur la communauté microbienne des eaux de surface. Cette étude a également mis en évidence la relation existante entre les échanges CO2 et d'O2 entre l'atmosphère et l'océan dans la WAP et la biomasse, la composition, la production primaire et la respiration de la communauté microbienne. Il existait tout d'abord une relation positive entre la concentration en Chl-a et la proportion de diatomées dans la communauté phytoplanctonique. De plus, il existait une corrélation négative significative entre la Chl-a et le ΔpCO2. La production primaire nette de la communauté (NCP) était principalement contrôlée par la production primaire et était négativement et positivement reliée avec le ΔpCO2 et le pourcentage de saturation de l'O2, respectivement, suggérant que la production primaire joue un rôle majeur dans les échanges de CO2 et d'O2 entre l'atmosphère et l'océan dans la WAP. Par ailleurs, le ΔpCO2 moyen au cours des trois années étudiées était de -20,04 ± 44,3 µatm, menant à un puits de CO2 potentiel durant l'été et l'automne dans la région. Le sud de la WAP était un puits potentiel de CO2 (-43,60 ± 39,06 µatm) durant l'automne alors que le nord de la WAP était principalement une source potentielle de CO2 durant l'été ou l'automne (-4,96 ± 37,6 et 21,71 ± 22,39 µatm, respectivement). Les plus fortes concentrations en Chl-a mesurées dans le sud de la WAP pourraient expliquer cette distribution spatiale
Regional warming in the western Antarctic Peninsula (WAP), along with the expected decrease in sea-ice cover and the seasonal ozone layer breakdown could modify the composition and the structure of the microbial community. In addition, these environmental changes could modify the potential of the WAP as a CO2 sink. In this context, this thesis aimed at evaluating the combined effects of regional climatic changes on the primary production and the composition and structure of the microbial community in the WAP. In a second time, this thesis aimed at evaluating the role of the microbial community structure, composition, primary production and respiration on air-sea CO2 gas exchanges.First, the variations in sea-ice cover, stratospheric ozone layer thickness and sea surface temperature over the last 30 years (1972-2007) were described. Related to the warming of WAP waters, the retreat of sea-ice was happening earlier each decade in the WAP. The observed changes in these environmental parameters offer a new temporal window for primary production. Indeed, the annual primary production increased from 1997 to 2007, in relation with the sea-ice cover anomaly for the previous winter. In addition, daily primary production was negatively and positively correlated to, respectively, sea-ice cover and sea-water temperature from September to November and from February to March, suggesting that regional warming favoured more primary production during spring and fall. On the contrary, the early retreat of sea-ice in spring, in coincidence with the spring ozone layer breakdown, led to an increase in photoinhibition (with an average of 11.6 ± 2.8 % of the daily primary production being photoinhibited). Therefore, regional climatic changes in the WAP had both a positive and a negative impact on primary production.The microbial community variability was also described in the Melchior Archipelago (in the WAP) from fall to spring 2006. Because of the extreme environmental conditions, the microbial community abundance and biomass were low in fall and winter and the community was dominated by small cells (< 2 µm), hence by a microbial food-web. Indeed, phytoplanktonic biomass was low during fall and winter (with respective chlorophyll a concentration, Chl-a, of 0.3 and 0.13 µg l-1). Phytoplankton biomass increased in spring (with a maximum Chl-a of 1.13 µg l-1) but, despite favourable growth conditions, phytoplankton was still dominated by small cells (2-20 µm), hence by a microbial or multivorous food-web. In addition, the early retreat of sea-ice in the spring 2006 exposed the WAP waters to strong ultraviolet B radiations (UVBR, 280-320 nm) that had a negative impact on the microbial community in surface waters.Finally, the relationship between air-sea CO2 and O2 exchanges in the WAP with the phytoplankton community biomass and composition and with the microbial community primary production and respiration was described. A positive relationship existed between Chl-a and the proportion of diatoms in the phytoplankton community. In addition, a negative relationship existed between Chl-a and ΔpCO2. The net community production (NCP) was mainly controlled by primary production and was negatively and positively related to ΔpCO2 and the %O2 saturation, respectively, suggesting that primary production was the main driver of air-sea CO2 and O2 gas exchanges in the WAP. In addition, the average ΔpCO2 for the summers and falls 2002 to 2004 was -20.04 ± 44.3 µatm, leading to a potential CO2 sink during this period in the WAP. The southern WAP was a potential CO2 sink (-43.60 ± 39.06 µatm) during fall while the northern part of the Peninsula was mainly a potential CO2 source during summer and fall (-4.96 ± 37.6 and 21.71 ± 22.39 µatm, respectively). The higher Chl-a concentrations measured in the southern WAP may explain this spatial distribution

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Washbourne, Carla-Leanne. „Engineering soils to act as carbon sinks“. Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2487.

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Soils containing calcium (Ca) and magnesium (Mg) bearing waste silicate minerals may be intentionally engineered to capture and store atmospheric carbon (C). Within the soil environment these minerals can capture and store atmospheric C through the process of weathering that releases Ca and Mg which then precipitate as carbonate minerals. Like natural silicates, silicate ‘wastes’ and artificial silicates sequester C through carbonation of calcium (Ca2+) and magnesium (Mg2+). Terrestrial CO2 sequestration may be promoted by the inclusion of these reactive mineral substrates in soils, and many waste sites and urban and anthropogenic soils already contain quantities of these materials. The UK Government is currently committed to reducing carbon emissions by 80% in 2050 (against a 1990 baseline) and soils have a role to play, acting as sinks for carbon. It is proposed that soil engineering measures could harness the high C turnover of the global pedologic system, ~120Pg C a-1 , to develop an efficient method of enhanced weathering. Artificial silicates have the potential to capture 192-333 Mt C a-1 , representing 2.0-3.7% of contemporary global C emissions; natural silicates present a carbon capture potential many orders of magnitude greater. Mineral carbonation in an artificial soil setting has the potential to capture inorganic carbon comparable to organic carbon accumulation. Soils of this type can accumulate 20-30 kg C m2 as carbonates (≥ organic carbon content in natural soils, ~17.5 kg C m2 for rural soils in the UK). Laboratory investigations were carried out on a number of experimental scales, from meso-scale flow-through reactors to micro-scale batch experiments, to determine the rate at which Ca and Mg could be supplied from suitable materials in engineered soil systems to perform a carbon capture function. Environmental factors were controlled for each in order to constrain their contribution to the overall process. Batch experiments were carried out at standard temperature and pressure (STP) to investigate effects of changes in solute concentration, water chemistry, agitation and particle size. pH controlled experiments were run at STP from pH 3-8, to determine the effects of pH changes on the weathering of wollastonite. Flow-through weathering experiments at STP investigated the effects of time, water chemistry, hydrogeological conditions and addition of CO2 on the weathering of steel slag. Analytical results demonstrate that Ca leaches rapidly from a number of Ca-rich artificial minerals providing great potential for carbon capture to occur on human-relevant timescales. Steel slag was shown to weather at a log rate of -9.39 to -11.88 mol Ca m-2 sec-1 in laboratory settings and -7.11 to - 7.56 mol Ca m-2 sec-1 under ambient environmental conditions in the field over 975 days. Anthropogenic soils, known to contain substantial quantities of Ca and Mg-rich minerals derived from industrial and demolition activity (including iron and steel slag, cement and concrete), were systematically sampled across two field sites. Analysis illustrated mean soil carbonate values of 21.8 ± 4.7% wt to 41.16 ± 9.89 wt % demonstrating that a large quantity of soil carbonate forms and persists in these environments, formed at a rate of 18kg CO2 t-1 a-1 . Stable isotope data ( 13C, 18O) confirm that up to 81% of C in these pedogenic carbonates is atmospherically derived. 14 C data also suggest that a significant proportion of the C present in carbonates analysed is ‘modern’. Applying a current CO2 trading cost of £8-£12 t-1 CO2, the potential value of CO2 sequestration at a study site was calculated to be £51,843 £77,765 ha-1 after 58% of its carbonation potential had been exploited. The studies contained in this thesis add to a growing body of evidence for the formation of carbonate minerals in soil settings where Ca/Mg-bearing silicate minerals occur. They also support the idea that engineered soils could be effectively utilised for carbon sequestration. Soil engineering for carbon capture provides a comparatively cheap, easy and attractive way of beginning to offset the environmental impact of certain industrial processes. Carbonation of waste silicates is a useful exercise in ‘closing the loop’ on C emissions produced in their manufacture. Carbon capture taking place on sites containing industrial waste materials is of interest to a variety of stakeholders: site owners, third sector bodies and local and national legislative bodies. Effective, low- energy field-scale implementation of mineral carbonation through soil engineering could assuage current constraints on economic performance of enhanced weathering technologies and highlight the importance of soil carbon storage.

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Schirber, Michael Robert. „Sources, sinks and scatterers of the ultra-violet background“. The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1072842778.

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Schirber, Michael. „Sources, sinks and scatterers of the ultra-violet background“. Columbus, Ohio Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1072842778.

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Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xiv, 250 p.; also includes graphics (some col). Includes abstract and vita. Advisor: Terry Walker, Dept. of Physics. Includes bibliographical references (p. 227-250).

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Butenhoff, Christopher Lee. „Investigation of the sources and sinks of atmospheric methane“. PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/2813.

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The work presented here represents a number of independent studies that investigated various components of the CH4 budget, namely the sources and sinks. We used a chemical-tracer model and created unique long-term time series of atmospheric CH4, carbon monoxide (CO), molecular hydrogen (H2), and methylchloroform (CH3CCl3) measurements at marine background air to derive histories of atmospheric hydroxyl radical (OH) - the main chemical oxidant of CH4, biomass burning - an important source of CH4 in the tropics, and emissions of CH4 from rice paddies - one of the largest anthropogenic sources of CH4, over decadal scales. Globally gridded inventories of CH4 emissions from rice paddies and terrestrial vegetation were created by synthesizing greenhouse and field CH4 fluxes, satellite-derived biophysical data, and terrestrial geospatial information.

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Shirsat, Shital. „Sources, transport and sinks of sulphur in the Antarctic troposphere“. Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611813.

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20

Simmons, Sarah L. „Sources, pathways and sinks of litter within riverine and marine environments“. Thesis, University of South Wales, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386562.

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This research was developed as one of the first studies to investigate riverine litter problems. Baseline assessment methods were formulated to define the scope and nature of this pollution form. Assessments were carried out in three catchments; the Taff East Lyn and Avill. The Taffwas found to be atypical regarding the extent of the litter. In all catchments plastic sheeting formed the principal litter component. The study also included an examination of the factors influencing the sources, pathways and sinks riverine litter pollution. These factors were drawn together through the development of a research model. Assessments of two quantifiable sources, sewage inputs through Storm Water Overflows (SWOs) and fly-tipping wastes, were undertaken. Greatest inputs of sewage-derived solids were introduced to the river through malfunctioning SWOs, the most numerous single component being sanitary towels. Whilst sewage-derived material constituted approximately 23% of all items on the River Taff large quantities of waste, especially plastic sheeting, originated from fly-tipping sites. Mobility of litter once introduced to the system was greatly dependent on river flow regimes. Some litter types, e.g. plastic sheeting, were more mobile than others and tended, after floods, to be stranded on vegetation. Due to its high profile within the catchments and expected longevity, plastic sheeting was chosen for river-bank degradation trials. Results indicated that photodegradation occurred within samples, but only in the initial exposure period and that any further breakdown was likely to result from physical abrasion. Marine areas were considered to be potential sinks for riverine litter, especially its more mobile components. An alternative sink for certain litter types such as cloth might be incorporation into the river-bank due to an ability to aggregate soil/sediment particles.

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Jensen, Alexa Lunt. „Evaluating Nitrogen and Carbon Differences in Standing Litter from Normal and Prematurely Senesced Bromus tectorum Plants“. BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8265.

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Bromus tectorum, an invasive winter annual, has displaced native vegetation throughout the western United States. Bromus tectorum litter influences nutrient cycling near the soil surface as well as plant establishment. Failed seed production of B. tectorum occasionally occurs in the field, with plants exhibiting weak flowering culms that turn straw-colored in spring when normal plants are green or purple in color. Because annual grasses transport most soluble carbon (C) and nitrogen (N) to reproductive organs, seed production failure results in significantly different fates for these nutrients compared with normal plants. As part of larger efforts to understand events leading to large-scale seedling emergence failure (termed die-offs), occasionally observed in near mono-cultures of B. tectorum, we here test the hypothesis that prematurely senesced litter associated with seed production failure has higher soluble C and N than normal litter. C and N concentrations of aboveground biomass were compared for normal and prematurely senesced B. tectorum plants. Two methods were used to cause premature senescence: fungal pathogen infection with Clarireedia capillus-albis and glyphosate herbicide application. In a related experiment, field sampling of normal and prematurely senesced plants under natural conditions was conducted to compare C and N levels in-situ. Herbicide-induced senescence resulted in 1.5 to 2 times greater soluble C concentrations, but fungal infection had no effect on soluble C under experiment conditions. Prematurely senesced litter had increased total N concentrations, resulting in lower C:N ratios. The C:N ratio for prematurely senesced plants (averaged across all studies) was 68:1, whereas mature normal plants averaged 243:1. These findings illustrate failed seed production associated with premature senescence results in B. tectorum litter with significantly higher N concentrations and can result in increased soluble C concentrations. Altered nutrient status may contribute to changes in soil microbial activity, including activity of soilborne pathogens found in die-offs.

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Clark, Daniel G. „Physical and biological sources and sinks of nitrate in the Canary basin“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24817.pdf.

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23

Plum, Sara A. „Manipulation of sources and sinks of grasses : growth, photosynthesis and root exudation“. Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389504.

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24

Burgess, Rachel. „Sources and sinks of Câ†2-Câ†8 hydrocarbons in the atmosphere“. Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297486.

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25

Wittig, Sophie. „Estimating methane sources and sinks in the Arctic using atmospheric data assimilation“. Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASJ002.

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L'Arctique est une région critique pour le changement climatique. Les températures aux hautes latitudes Nord augmentent environ trois fois plus vite que la moyenne mondiale : les changements environnementaux tels que la diminution de l'étendue de la banquise ou le dégel du pergélisol progressent donc rapidement. En conséquence, des rétroactions climatiques positives sont déclenchées dans cette région, ce qui accélère encore son réchauffement. L'un de ces changements est la possible augmentation des émissions de méthane (CH4). Le CH4 est un puissant gaz à effet de serre dont la concentration moyenne mondiale dans l'atmosphère a augmenté d'environ 160 % depuis l'ère préindustrielle, une tendance qui se retrouve en Arctique. Actuellement, diverses sources de CH4, naturelles et anthropiques, contribuent aux émissions en Arctique. Les émissions anthropiques sont principalement dues à l'extraction et à la distribution de combustibles fossiles par les nations arctiques. La principale source naturelle de CH4 est constituée par les zones humides situées aux hautes latitudes Nord, mais d'autres systèmes d'eau douce, les feux de forêt, des flux géologiques et des émissions océaniques de différentes origines contribuent également au bilan de CH4 de l'Arctique. En outre, le dégel et la déstabilisation du pergélisol terrestre et sous-marin pourraient augmenter les émissions de CH4 dans un avenir proche, par exemple en raison de l'exposition de la matière organique du sol. Cependant, l'évaluation des émissions de CH4 en Arctique et de leur contribution au budget mondial reste difficile. Cela est dû, d'une part, aux difficultés à effectuer des mesures dans des zones aussi difficiles d'accès. D'autre part, de fortes variations dans la distribution spatiale des sources de méthane et une mauvaise compréhension des effets des changements en cours sur la décomposition du carbone, la végétation et l'hydrologie compliquent l'évaluation. Le but de ce travail est donc de réduire les incertitudes sur les estimations actuelles des émissions de CH4 grâce à une approche de modélisation inverse pour mieux quantifier les sources et les puits de CH4 pour les années récentes (2008 à 2019). Plus précisément, il s'agit de détecter les tendances des émissions de CH4 et les changements éventuels dans les cycles saisonniers et d'analyser la capacité du réseau d'observation in-situ actuel à caractériser les différents secteurs et les tendances futures potentiellement causées par une "bombe à méthane". La mise en œuvre de l'inversion comprend des simulations par le modèle de transport atmosphérique FLEXPART, des émissions provenant d'inventaires et de modèles biogéochimiques et des données de concentrations atmosphériques de CH4 en 42 sites d'observation dans différentes nations arctiques. Les résultats de l'inversion montrent que la majorité des sources de CH4 actuellement présentes aux hautes latitudes sont peu contraintes par le réseau d'observation existant. On ne peut donc tirer des conclusions sur les tendances et les changements dans le cycle saisonnier pour les secteurs correspondants. Seuls les flux de CH4 des zones humides sont suffisamment contraints, principalement en Amérique du Nord. Au cours de la période étudiée, les émissions des zones humides ont une légère tendance négative en Amérique du Nord et une légère tendance positive en Eurasie orientale. Dans l'ensemble, les émissions de CH4 obtenues sont inférieures aux estimations ascendantes mais supérieures aux résultats des inversions globales. La contrainte insuffisante du réseau d'observation se retrouve dans un scénario simulant des augmentations futures des émissions de CH4. Les tendances appliquées ont non seulement été détectées de manière incorrecte dans les régions où elles étaient prescrites mais encore, des émissions élevées de CH4 ont été attribuées à des zones où aucune tendance n'était présente. Un hypothétique réseau d'observation étendu ne montre que des améliorations mineures
The Arctic is an especially critical region with regard to global climate change. With temperatures in high northern latitudes increasing around three times faster than the global average, changes in environmental characteristics such as declining sea ice extend or thawing permafrost soils are proceeding rapidly. As a consequence, positive climatic feedbacks are triggered in this region, whereby the Arctic warming is accelerated even further. One important impact is the high risk of increased methane (CH4) emissions. CH4 is a potent greenhouse gas whose global average concentration in the atmosphere has increased by about 160 % since pre-industrial times, a trend that is also reflected in the Arctic. Currently, various CH4 sources, both natural and anthropogenic, are contributing to CH4 emissions from the Arctic region. Anthropogenic emissions are predominantly caused by the extraction and distribution of fossil fuels by the Arctic nations. The dominant natural source of CH4 are high northern latitude wetlands; however, other freshwater systems, wildfire events, geological fluxes and oceanic emissions of different origins also contribute to the Arctic CH4 budget. Furthermore, the thawing and destabilization of terrestrial and sub-sea permafrost will potentially increase CH4 emissions in the near future, for instance by the exposure of degradable soil organic matter. However, assessing the amount of CH4 emissions in the Arctic and their contribution to the global budget still remains challenging. This is on the one hand due to the difficulties in carrying out accurate measurements in such remote areas. Besides, high variations in the spatial distribution of methane sources and a poor understanding of the effects of ongoing changes in carbon decomposition, vegetation and hydrology also complicate the assessment. Therefore, the aim of this work is to reduce uncertainties on current bottom-up estimates of CH4 emissions as well as soil oxidation by implementing an inverse modeling approach in order to better quantify CH4 sources and sinks for the most recent years (2008 to 2019). More precisely, the objective is to detect occurring trends in the CH4 emissions and potential changes in seasonal emission patterns as well as to analyze the capability of the current stationary observation network in the Arctic to constrain the different CH4 sectors and to detect possible future trends caused by a potential “methane bomb”. The implementation of the inversion included hereby footprint simulations obtained with the atmospheric transport model FLEXPART, various emission estimates from inventories and land surface models as well as data of atmospheric CH4 concentrations from 42 surface observation sites in the Arctic nations. The results of the inversion showed that the majority of the CH4 sources currently present in high northern latitudes are poorly constrained by the existing observation network. Therefore, conclusions on trends and changes in the seasonal cycle could not be obtained for the corresponding CH4 sectors. Only CH4 fluxes from wetlands are adequately constrained, predominantly in North America. Within the period under study, wetland emissions show a slight negative trend in North America and a slight positive trend in East Eurasia. Overall, the estimated CH4 emissions are lower compared to the bottom-up estimates but higher than similar results from global inversions. The insufficient constraint by the observation network is also shown by a hypothetical scenario simulating future increases in CH4 emissions. Thereby, the applied trends are not only incorrectly detected in the regions they are assigned to, but elevated CH4 emissions are also attributed to areas where no trend is given by the scenario. A hypothetical expanded observation network of stationary sites show hereby only minor improvements

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Yoshida, Yasuko. „Global sources and distribution of atmospheric methyl chloride“. Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-06232006-151220/.

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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.
Robert Dickinson, Committee Member ; Athanasios Nenes, Committee Member ; David Tan, Committee Member ; Armistead Russell, Committee Member ; Yuhang Wang, Committee Chair.

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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.

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Nagarathnam, Premkumar. „Novel carbon nanotube thermal interfaces for microelectronics“. Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31720.

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Graham, Sam; Committee Member: Joshi, Yogendra; Committee Member: Kalaitzidou, Kyriaki. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Stout, Justin Collin. „Identifying and quantifying sediment sources and sinks in the Root River, Southeastern Minnesota“. DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1304.

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Currently, our ability to predict the flux of fine sediment at the watershed scale is limited by the precision of erosion rate estimates for the many potential sources distributed throughout a landscape as well as our understanding of the connectivity of sediment pathways during transport. In absence of a robust predictive model which can be validated by measurements of sediment fluxes and use of geochemical tracers. Predicting fine sediment yield at the watershed scale requires multiple redundant lines of information. This thesis outlines the methods used, and the data sets collected in the Root River watershed in Southeastern Minnesota, all of which are multiple lines of evidence to the sediment dynamics in the Root River. The research indicates that the Root River is a very dynamic watershed. The hydrologic regime of the watershed has shifted over the last half century. Due to this shift sediment fluxes are very dependent of the magnitude and sequence of events. Geomorphic analysis of the landforms and the use of a developed tool, TerEx, indicate that many reaches of the river have easily accessible near-channel sources of sediment. Sediment fingerprinting results illustrate that source tracer concentrations are variable across the landscape, that as a whole, upland sources are still a major contributor to the suspended sediment load, and that in some sub-watersheds near-channel sources are dominate in the suspended load. Over all the channel-floodplain exchange exerts strong control on the flux of sediment through this river system.

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Ahmad, Ismariah. „Economics of carbon emission and sequestration in the Malaysian forest sector /“. Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5588.

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Fuss, Sabine, Wolf Heinrich Reuter, Jana Szolgayova und Michael Obersteiner. „Optimal mitigation strategies with negative emission technologies and carbon sinks under uncertainty“. Springer Netherlands, 2013. http://dx.doi.org/10.1007/s10584-012-0676-1.

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In recent years a body of literature has arisen on the topic of how to compose the optimal portfolio of mitigation options. The focus has been mainly on options involving shifts from high- to low- or even negative-carbon technologies. Natural sinks play an important role in any attempt to stabilize atmospheric CO2 and usually enter as a constant term in the overall carbon budget. In this paper, we introduce natural sinks to the carbon management problem and analyze the implications for negative emission technology deployment and the overall mitigation strategy. Amongst other sensitivity analyses, we also investigate the impact of uncertainty in the carbon sink, which we find to raise the importance of negative emissions in the mitigation portfolio significantly lowering the cost of the policy mix. (authors' abstract)

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Potouroglou, Maria. „Assessing the role of intertidal seagrasses as coastal carbon sinks in Scotland“. Thesis, Edinburgh Napier University, 2017. http://researchrepository.napier.ac.uk/Output/975386.

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Seagrasses are marine foundation species that form ecologically important habitats in coastal areas around the world. They provide a range of ecosystem services, including coastal protection and the recently recognised large contribution to global carbon sequestration and storage. To date, the majority of published studies on the aforementioned ecosystem services is limited to specific geographic regions and seagrass species. This PhD study attempted to explore and provide the first evidence, to the best of our knowledge, on the role of Scottishseagrasses as carbon sinks and sediment stabilisers. In 2013, shoot dynamics of Zostera noltii plots were monitored biweekly and seasonally in the Forth estuary and digital images of the surveyed plots were taken for the development of a remote sensing technique which would accurately estimate the vegetation cover. In 2014, sediment samples from vegetated and unvegetated plots within beds of Z. marina and Z. noltii were collected from all the major estuaries along the east coast of Scotland, from the Firth of Forth in the south to Dornoch Firth in the north. Samples were analysed for organic matter, organic carbon, radionuclides 210Pb, 137Cs and 241Am, and δ13C in order to determine the organic matter and organic carbon density, longevity and sources of carbon respectively. To explore the role of seagrass in sediment deposition and stability, surface elevation was measured monthly in seagrass plots and bare sediment in the Forth estuary over two years. The results and main mechanisms underlying these findings are reported and discussed in detail in each chapter. In short, the proposed method based on digital images provided estimates of seagrass coverage that are more accurate than observers' estimates, with some constraints when macroalge and/or extreme light are present. Intertidal seagrass meadows in Scotland showed significantly enhanced carbon storage compared with bare sediment. Seagrass plots contained variable quantities of carbon in their sediments with species composition having a significant effect on carbon stocks, whereas depth and seagrass abundance had no effect on carbon stores. Despite their small above-ground biomass Scottish seagrass plots had a strong influence on sediment deposition and prevented erosion. Further research is needed to understand what factors drive large carbon sequestration and storage at some sites, thus contributing policy-relevant information on the prediction of the seagrass carbon hot-spots. Also, long-term datasets on surface elevation change are important in order to understand the effect of all the processes involved on sediment deposition in seagrass beds.

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Hughes, Andrew Owen Physical Environmental &amp Mathematical Sciences Australian Defence Force Academy UNSW. „An assessment of recent changes in catchment sediment sources and sinks, central Queensland, Australia“. Awarded by:University of New South Wales - Australian Defence Force Academy. Physical, Environmental & Mathematical Sciences, 2009. http://handle.unsw.edu.au/1959.4/43622.

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Spatial and temporal information on catchment sediment sources and sinks can provide an improved understanding of catchment response to human-induced disturbances. This is essential for the implementation of well-targeted catchment-management decisions. This thesis investigates the nature and timing of catchment response to human activities by examining changes in sediment sources and sinks in a dry-tropical subcatchment of the Great Barrier Reef (GBR) catchment area, in northeastern Australia. Changes in catchment sediment sources, both in terms of spatial provenance and erosion type, are determined using sediment tracing techniques. Results indicate that changes in sediment source contributions over the last 250 years can be linked directly to changes in catchment land use. Sheetwash and rill erosion from cultivated land (40-60%) and channel erosion from grazed areas (30-80%) currently contribute most sediment to the river system. Channel erosion, on a basin-wide scale, appears to be more important than previously considered in this region of Australia. Optically stimulated luminescence and 137Cs dating are used to determine pre-and post- European settlement (ca. 1850) alluvial sedimentation rates. The limitations of using 137Cs as a floodplain sediment dating tool in a low fallout environment, dominated by sediment derived from channel and cultivation sources, are identified. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times) are attributed to the naturally high sediment loads in the dry-tropics. These low increases suggest that previous predictions which reflect order of magnitude increases in post-disturbance sediment yields are likely to be overestimates. In-channel bench deposits, formed since European settlement, are common features that appear to be important stores of recently eroded material. The spatially distributed erosion/sediment yield model SedNet is applied, both with generic input parameters and locally-derived data. Outputs are evaluated against available empirically-derived data. The results suggest that previous model estimates using generic input parameters overestimate post-disturbance and underestimate predisturbance sediment yields, exaggerating the impact of European catchment disturbance. This is likely to have important implications for both local-scale and catchment-wide management scenarios in the GBR region. Suggestions for future study and the collection of important empirical data to enable more accurate model performance are made.

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Ong, Ahchuan. „Diagnostic initialization generated extremely strong thermohaline sources and sinks in the South China Sea“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FOng.pdf.

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Bradshaw, Leslie C. „Sources and sinks of nitrogen in the Cape Fear River estuary, southeastern North Carolina /“. Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/bradshawl/lesliebradshaw.html.

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Rondeau, Marine. „Floraison de la vigne et changement climatique : effet de l’augmentation de la température sur le métabolisme carboné au cours du développement floral“. Thesis, Reims, 2018. http://www.theses.fr/2018REIMS043.

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Les études portant sur le changement climatique prévoient des modifications significatives de la température pour les décennies à venir. Ces prévisions envisagent un réchauffement global qui risque de perturber le développement des plantes cultivées. Les stress thermiques affectent en effet presque tous les aspects du développement des plantes et notamment la croissance, le développement floral et donc le rendement. Les plantes doivent modifier leur métabolisme afin de prévenir les dommages causés par les stress environnementaux. La température joue un rôle important sur la phénologie, la vigueur et surtout le développement floral de la vigne. Ainsi, quelques degrés d’élévation de la température pendant la floraison peuvent entrainer la perte de la totalité des fleurs et donc des fruits. De plus, en stimulant le développement végétatif, l’augmentation de température accroit la demande en glucides, tandis que la photosynthèse nette diminue en raison de l’augmentation de la respiration en réponse à l’élévation de température. Au cours de cette étude, nous nous sommes intéressés à l’impact d’une augmentation de température sur le métabolisme carboné, acteur majeur de la floraison, et plus particulièrement aux modifications physiologiques de la feuille et de l’inflorescence de vigne. De plus, des analyses d’expression de gènes clés de la photosynthèse et du métabolisme ont permis d’améliorer la compréhension des mécanismes de distribution des glucides entre les organes végétatifs et reproducteurs lors d’une augmentation de la température
Studies on climate change predict significant changes in temperature for next decades. The global warming could impact the crop plants development. Indeed, thermal stresses affect almost all aspects of plant development including growth, floral development and yield. Plants modify their metabolism to prevent damage caused by environmental changes. Temperature is an important factor for the phenology, the vigor and especially the floral development in grapevine. So, a few degrees increase during flowering can result in a complete flowers loss and therefore fruits. In addition, an increase of temperature stimulates vegetative development and thus rises the carbohydrates consumption, while net photosynthesis decreases due to the respiration raise. In this study, we investigated the temperature increase impacts on the carbon metabolism which has a major role in the flowering process in grapevine. We particularly focused our attention on the physiological modifications in leaves and inflorescences. at the level of the photosynthesis and the respiration with the increase of the day temperature. Moreover, expression analyzes of some key genes involved in photosynthesis and metabolism allowed to improve the understanding in the carbohydrate distribution mechanisms, between vegetative and reproductive organs, during a temperature increase

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Sonnerup, Rolf Erik. „Reconstructing the oceanic ¹³Seuss effect /“. Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/11026.

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Dymond, Caren. „Disturbance and climate change risks to forest carbon sinks and potential management responses“. Thesis, Bangor University, 2018. https://research.bangor.ac.uk/portal/en/theses/disturbance-and-climate-change-risks-to-forest-carbon-sinks-and-potential-management-responses(416a28ec-8724-43f6-a415-513772dd7dc2).html.

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Climate change is a global crisis facing forest management. There are risks to many ecological goods and services from forests due to changes in productivity, mortality, pathogen, and wildfire dynamics. Likewise, there are opportunities such as increases in productivity or targeted funding for climate adaptation and emission reductions. To manage those risks and opportunities, we need the fundamental knowledge of forest carbon (C) cycles. Overall, my dissertation aims to improve our understanding of forest carbon dynamics and how they may respond to natural disturbances, climate change and management activities. This purpose falls within the context of the need to adapt to and mitigate climate change for the ongoing provision of ecological goods and services from forest ecosystems such as timber and biodiversity. The thesis starts with a critical analysis of six papers I have previously published. That chapter includes a synthesis of findings, critique of methods used, and identifies some areas for future research. Each subsequent chapter represents a contributing article. The overall findings of this dissertation are (i) that although forests are often GHG sinks moderate or high intensity natural disturbances can reverse that flux. (ii) That climate change effects on productivity may increase or decrease the natural sinks or even create emission sources in forests that may otherwise have been sinks. (iii) That management strategies to increase species diversity and resilience may be effective at reducing risks of emissions, but they must be assessed for individual ecosystems and may be insufficient to fully offset disturbance or climate change effects.

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Mann, Mark. „Carbon nanotubes as electron gun sources“. Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612202.

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Alem, Hubert. „Impact of the carbon source/sink balance on glycosylated aroma precursor accumulation in grapevine fruit (Vitis vinifera L.)“. Thesis, Montpellier, SupAgro, 2018. http://www.theses.fr/2018NSAM0062.

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Les composés aromatiques sont des métabolites secondaires qui jouent un rôle clé dans la qualité du raisin. Les terpènes, les C-13 norisoprénoïdes, les phénols et les alcools non terpéniques sont les composés aromatiques les plus importants dans les raisins et peuvent être accumulés sous forme de molécules libres volatiles ou glyco-conjugués. Le groupe des précurseurs aromatiques glycosylés (GAP) est le plus important et il est présent dans toutes les variétés de Vitis vinifera (L.), l'espèce la plus largement utilisée pour la production de vin. Les GAP représentent 80 à 90% du potentiel aromatique du raisin selon le cultivar. Les pratiques agronomiques telles que l'irrigation, les systèmes de formation, l'effeuillage et l'éclaircissage des régimes peuvent avoir un impact sur le développement de la plante et des fruits. La modification de la relation source/puits (S/P) dans le but d'augmenter la qualité des raisins et une pratique très courante en viticulture. Ces pratiques comprennent l'éclaircissage, l'écimage et le contrôle du nombre de bourgeons par plante. L'éclaircissage, est une pratique très rependue en viticulture et ayant un impact direct sur le rapport S/P, alors qu'il n’y a pas beaucoup de travaux sur l’effet réel de l’éclaircissage sur l'accumulation des GAP. Dans de nombreux cas, les cahiers des charges des AOP et d'IGP prévoient une limite du rendement en fruits par hectare. Ensuite, les viticulteurs régulent les rendements en gérant le nombre de bourgeons/hectare et/ou en éclaircissant les fruits.L'objectif principal de nos travaux etait d'analyser l'impact des modifications du rapport S/P sur la biosynthèse des GAP. Les GAP ont été choisis car : i) ils sont présents dans tous les cultivars de Vitis vinifera, ii) ils représentent la plus grande source de molécules aromatiques potentielles et iii) car ces molécules incorporant des groupes glycosylés, leur accumulation dépend de la fourniture en hydrates de carbone donc potentiellement de la balance carbonée de la plante.L'objectif principal de nos travaux a concerné l'étude de l'impact du rapport source/puits sur la biosynthèse des GAP, et sa modulation éventuelle en fonction du génotype. Cinq questions ont été abordées : 1) L'influence du génotype sur la biosynthèse des GAP et son accumulation à un stade de maturité donné. 2) L'influence de l’année sur la croissance du raisin et l'accumulation des GAP. 3) L'impact de l'équilibre S/P sur la biosynthèse des GAP exprimé en concentration (µg/L) et en quantité (µg/baie) en fonction du développement du raisin. 4) La relation entre les métabolismes primaire et secondaire (GAP et anthocyanes) et leur modulation en fonction de l'équilibre S/P. 5) Influence de la date d'éclaircissage sur la dynamique de biosynthèse des GAP.Les résultats ont montré que les teneurs en composés aromatiques glycosylés variaient en fonction du génotype. Les variétés dont les raisins contiennent des composés terpéniques (Muscat à petits grains blancs et l'hybride V. vinifera x Muscadinia rotundifolia G5) ont présenté les plus grandes teneurs en GAP aussi bien en concentration qu'en quantité par fruit. Ces mêmes génotypes ont montré les valeurs les plus élevées du rapport GAP/sucre. En général, les génotypes produisant des baies non colorées ont présenté des ratios GAP/sucre plus élevés que les variétés à baies colorées
Aroma compounds are secondary metabolites that play a key role in grape quality. Terpenes, C13-norisoprenoids, phenols and non-terpenic alcohols are the most important aroma compounds in grapes and can be accumulated as free volatile or glycoconjugated molecules. The non-volatile glycosylated aroma precursors (GAP) group is the largest one, and it is present in all varieties of Vitis vinifera (L.), the most widely-used species for wine production. Agronomic practices such as irrigation, training systems, leaf removal and bunch thinning can impact the plant and fruit development. The modification of the source/sink relationship (S/S) with the scope of increasing the grape quality, is very common between viticulturists. These practices include bunch thinning, pruning, and the election of the number of buds/plant. Bunch thinning, a very extended practice in viticulture and which directly impacts on S/S, is one of the less researched practice regarding GAP. In many cases, DOC and IGT production protocols include a limit in the fruit yield per hectare. Then, viticulturists regulate yield by managing number of buds/hectare and/or by fruit thinning.The main objective of our work was to analyze the impact of the modifications of S/S balance on the biosynthesis of GAP. GAP are chosen in this research because: 1) they are present in every cultivar of Vitis vinifera, 2) they represent the biggest source of potential aromatic molecules, and 3) because these molecules incorporate glycosyl groups, their accumulation depends on the supply of carbohydrates and potentially on the carbon balance of the plant. The main objective of our work concerned the study of the impact of the S/S ratio on the biosynthesis of GAP, and its possible modulation depending on the genotype. Five questions were addressed: 1) Influence of the genotype on in the biosynthesis of GAP and its accumulation. The objective is to analyze the variability of GPA concentration at a given maturity stage among genotypes, including a set of varieties of V. vinifera (Marselan, Grenache, Muscat, Cabernet Sauvignon, Syrah and Chardonnay) and hybrids. V. vinifera x Muscadinia rotundifolia (G5). 2) Influence of the year on S/S balance and GAP concentration. 3) The impact of the S/S balance on the biosynthesis of GAP expressed in concentration (µg/L) and in quantity (µg/berry) as a function of grape development. 4) The relationship between primary and secondary metabolism (GAP and anthocyanins) and their modulation as a function of S/S balance. 5) Influence of the thinning date on the dynamics of GAP biosynthesis.The results showed that levels of glycosylated aromatic compounds varied according to genotype. Varieties whose grapes contain terpenic compounds (Muscat à petits grains blancs and the V. vinifera x Muscadinia rotundifolia G5 hybrid) showed the highest levels of GAP in both concentration and amount per fruit. These genotypes showed the highest values of GAP/sugar ratio. In general, genotypes producing non-colored berries had higher GAP/sugar ratios than colored berries. Despite strong inter-annual variation, the impact of the S/S ratio on GAP biosynthesis was found to be genotype-dependent.Thus, the GAP concentration was not affected during the modification of S/S in Cabernet-Sauvignon, while Muscat and Syrah showed large variations in GAP/berry contents as a function of the S/S ratio. The thinning date was also an important modulating factor in the increase of GAP, but varies according to genotype. In general, a significant decrease in the amount of primary metabolites accumulated in grapes is required to significantly increase the biosynthesis of secondary metabolites. This gain is very notable for anthocyanins, which are the most abundant carbon compounds after the primary metabolites (sugars and organic acids) in grapes. With regard to aromatic precursors, the impact is more moderate regardless of the family of glycosylated compounds

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Zeng, Sibo [Verfasser]. „The evolution of carbonate weathering carbon sinks under climatic and anthropogenic perturbations / Sibo Zeng“. Berlin : Freie Universität Berlin, 2021. http://d-nb.info/1238595804/34.

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McCallister, Leigh. „Organic matter cycling in the York River estuary, Virginia: An analysis of potential sources and sinks“. W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539616768.

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A study of the organic matter (OM) sources and biogeochemical and physicochemical sinks was undertaken in the York River estuary, Virginia. The reactivity of dissolved organic carbon (DOC) was enhanced from ∼25--68% by the combined effects of exposure to natural sunlight and bacterial decomposition. In contrast, sunlight exposure decreased the bioreactivity of DOC in the higher salinity lower York by a factor of five. The combined effects of photochemical and bacterial processing were found to modify both the bioavailability and metabolic fate of OM (e.g. respiration vs. biomass). Stable isotopic (delta13C, delta15N) and radiocarbon (Delta14C) values of bacterial nucleic acids were used to estimate the sources and ages of OM assimilated by bacteria in the York and Hudson River estuaries. Bacterial production in freshwater regions of the York was fueled by OM of young, terrigenous origin which accounted for 42--89% of OM assimilated. The remainder (11--58%) of OM assimilated was derived from freshwater algae. In the mid-salinity York, bacterial production was supported by phytoplankton-derived OM in the spring and summer (93--100%) and marsh-derived OM in the fall (73--100%). Isotopic values of bacteria in the lower York suggested production was supported by phytoplankton-derived OM (86--100%) in July and November and algal and marine-like OM (50--69%) in October. In contrast to the young (10--20 yr) OM assimilated by bacteria in the York, production in the Hudson River was subsidized by old (∼1200 BP) terrigenous OM. Higher C:N ratios, lower delta13C and delta 15N values and depletions of total lipid and lipid compound classes in high molecular weight dissolved organic matter (HMW DOM (≥3kDa)) relative to particulate organic matter (POM), suggested differences in the reactivity and cycling of these two OM fractions. Within the dissolved pool, polyunsaturated fatty acids (FA) were a strong predictor of DOC decomposition in bioassays. FA and sterol distributions suggest that POM is derived from phytoplankton/zooplankton sources, while HMW DOM has a bacterial and vascular plant signature. Thus, the physical form of OM (particulate vs dissolved) may affect both the distribution and biogeochemical processing of OM such that terrigenous DOM may be exported, while POM is retained within the estuary.

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Jensen, Christopher D. (Christopher David) 1974. „Terrestrial sources and sinks of atmospheric methyl bromide : three-dimensional modeling of tropospheric abundance and sensitivities“. Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/54436.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999.
Includes bibliographical references (p. 87-92).
Current estimates of methyl bromide surface fluxes are inconsistent with the observed tropospheric mole fractions (9 to 10 ppt, globally averaged) and the calculated atmospheric lifetime (1.7 ± 0.2 years), with mid-range estimates of sinks exceeding sources by at least 50 Gg y-I. Given the uncertainties in process-specific surface flux estimates, we consider several distributions of terrestrial sources and sinks that satisfy the constraints on atmospheric abundance, Mole fractions corresponding to each distribution are simulated with a three-dimensional chemical transport model based on analyzed observed winds, coupled to a simple model of the ocean mixed layer. All of the resulting scenarios overestimate the observed zonal gradient, with interhemispheric ratios ranging from 1.39 to 1.60. In the absence of unknown sources, model results imply a biomass burning source near the upper limit of the range of present estimates (50 Gg y-1). Sensitivities to surface fluxes are also calculated to determine the extent to which uncertain terms in the methyl bromide budget can be better quantified using long-term measurements. Results show that a global network capable of accurately monitoring the monthly, zonal mean distribution of CH3Br would be able to distinguish between biomass burning fluxes and other known terrestrial sources and sinks. Modeled sensitivities to biomass burning emissions also highlight the importance of including tropical locations in any long-term monitoring network. However, technological sources and soil sinks have similar zonal patterns, and long-term, "background" mole fractions are relatively insensitive to zonal flux distributions. It is only when we examine the high frequency variability of the concentration that the effect of longitudinal gradients in the flux field becomes apparent.
by Christopher D. Jensen.
S.M.

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Weston, Johanna Nadia Jean. „Quantification of nitrate sources and sinks using a water quality network in Morro Bay Estuary, California“. DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/634.

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Using an instrumented water quality network in Morro Bay Estuary, California from 2007 to 2010 (15 min sampling frequency), this study addressed the two objectives of constructing a nitrate budget and assessing the influence of sampling frequency on water quality parameters. These two objectives led to the submission of an original report of research (Appendix A) and a note (Appendix B) to peer-reviewed journals. The first objective was to characterize the high spatial and temporal variation in physical parameters and nitrate concentrations and to construct a nitrate budget quantifying sources and sinks of nitrate from the ocean, streams, and groundwater, as well as biological processes in the Estuary. Morro Bay Estuary was found to be a non-eutrophic system and a mean net exporter of nitrate, 327.15 t yr-1. Fifty-four percent of the nitrate export was attributed to nitrate sources and internal biological processing. Nitrate loading from streams contributed 37 % to the export of nitrate (124.01 t yr-1), while groundwater nitrate loading supplied a conservative estimate of 46 % of the exported nitrate (153.92 t yr-1), with a neap tide enhancement of the discharge. Denitrification, Zostera marina, and benthic macroalgae assimilation of nitrate were the dominant internal biological processes for removal and retention, but were only 35% of the total nitrate budget. The second objective was to investigate the impact of sampling frequency and sampling location on understanding dynamics in water quality by degrading a year time series of seven parameters from three water quality monitoring stations to sampling frequencies ranging from 15 minutes to 28 days. In Morro Bay Estuary, the semi-diurnal tidal cycle was the maximum component frequency driving the variability of temperature, turbidity, and dissolved oxygen concentrations. For these parameters, asymptotes were reached and sampling frequencies greater than six hours did not explain the additional variation in the parameters sampled. Whereas, salinity, turbidity, and nitrate concentrations lacked an asymptote, and decreased sampling frequencies led to increased estimated error. Sampling water quality parameters every 28 days can lead to mean annual difference of 30 – 140 % from 15 minute sample annual mean. We recommend sampling frequencies should be selected to oversample the tidal signal to at least hourly frequencies to capture diel cycles and episodic events that contribute significantly to understanding the variability in the estuarine physical and biological dynamics.

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Salinas, Zapata Cristian C. „Seagrass soils as paleoenvironmental tools and biogeochemical sinks for management“. Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2542.

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Coastal vegetation plays an essential role in regulating climate change and water quality, especially seagrass meadows that cover up to 1.6 million km2 worldwide and have been identified as globally significant filters and sinks of biogeochemical elements, including organic carbon (Corg) and nitrogen (N). Over the past century, the accelerating intensity and duration of natural and anthropogenic disturbances have caused severe regime shifts in estuarine and other coastal ecosystem dynamics, causing seagrass losses and affecting their valuable ecosystem services. Although knowledge of long-term seagrass ecosystem dynamics is scarce, including baseline conditions prior to major disturbances, the limited available information has been crucial to assess the human and natural impacts on coastal ecosystems. For example, it has provided answers to key questions related to seagrass ecology, climate change and management, including the estimation of the ecological significance and the monetary value of the biogeochemical sinks associated with seagrass ecosystems. This thesis aims to use seagrasses biogeochemical sinks as archives to reconstruct and understand : 1) baseline conditions in Australian estuaries, and spatial variability in environmental change, including perturbations that triggered the loss of seagrass meadows; 2) the significance of seagrasses in global biogeochemical cycles, as well as the processes that support their potential to store carbon and nitrogen; and 3) the losses of biogeochemical sinks as a consequence of seagrass meadow losses through human-induced impacts and extreme weather events. In this thesis, seagrass sedimentary archives encompassing the last few centuries have been studied to decipher centennial-scale environmental change in temperate estuaries, and the impacts of marine heatwaves and eutrophication on the Corg and N biogeochemical sinks associated to seagrass ecosystems. In the first data chapter of this thesis, the impact of land-use change on the ecological dynamics of temperate estuaries in Australia is reconstructed based on the analysis of multiple proxies in seagrass sedimentary archives encompassing the last 500 years. This palaeoecological study revealed the effect of land-use change following European settlement in the 1800s in Australia on the ecological condition of the estuaries, highlighting the deterioration of seagrass meadows following increased coastal development and agriculture activity after World War II. The second data chapter examined the effect of seagrass loss due to eutrophication on seagrass soil Corg stocks and fluxes, and provides pioneering estimates of CO2 emissions following disturbance of seagrass ecosystems that can be used to support the development of seagrass blue carbon projects (conservation and restoration) to mitigate climate change. The results showed that seagrass loss alone does not necessarily drive erosion of soil Corg, but when combined with sufficient hydrodynamic energy at the sediment surface ( > 0.20 m/s in this case), significant losses occurred (88–95% of soil Corg stocks). The study provided first-order estimates of potential CO2 emissions from eutrophication-induced seagrass loss since the 1950s in Australia, with 161,150 hectares of seagrass habitat loss that likely resulted in the release of 11–21 Tg CO2 (equivalent to a 2% increase in annual CO2 emissions from land-use change). These data will be crucial to inform the implementation of seagrass blue carbon into the Australian climate change mitigation policy. The third data chapter assessed soil N stocks and accumulation rates in Australian seagrass meadows, and provides pioneering estimates of soil N depletion following disturbance of seagrass meadows due to eutrophication and marine heatwaves, and identified the main drivers and potential ecological consequences of those losses. The results showed that Australian seagrasses capture 216–910 Gg N yr-1, equivalent to 96–105% of N runoff from Australian catchments. On the other hand, Australian-wide seagrass losses since the 1950s likely resulted in the loss of 435-720 Gg N from their soils, which likely enhanced eutrophication processes and resulted in adverse ecological consequences. This thesis provides novel and key information on the role of seagrasses as biogeochemical sinks and sources. This information can inform management practices of estuarine and other coastal ecosystems and highlights the value of seagrass sedimentary archives for determining baseline cycles and to reconstruct the time-course of ecological change in response to natural and anthropogenic disturbances. This thesis also highlights the need to conserve and restore seagrass meadows due to their value as natural archives and biogeochemical sinks, demonstrating their potential as a Natural-based Solution for contributing to climate change mitigation.

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Blank, Daniel [Verfasser], und Jürgen [Akademischer Betreuer] Zeddies. „Agriculture as emission source and carbon sink : economic-ecological modelling for the EU-15 / Daniel Blank. Betreuer: Jürgen Zeddies“. Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2011. http://d-nb.info/1027291759/34.

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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.

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Sneddon, Gregor. „Nanoporous carbon capture materials from sustainable sources“. Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3364.

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Rising CO2 levels in the atmosphere from anthropogenic sources can be seen as one of the greatest problems faced by mankind in modern history. CO2 capture and subsequent storage or utilisation is one possible solution to increasing CO2 levels in the short-term, until humanity is less reliant on fossil fuels. This thesis will investigate currently available state of the art CO2 capture technologies and provide a critical evaluation on their suitability. Furthermore, current research into the storage and utilisation of captured CO2 will also be studied and the long-term suitability of these approaches to increasing CO2 levels determined. New solid-state CO2 adsorption materials have been developed using waste polymeric materials as the primary agent for selective adsorption of CO2. The approach of using waste materials for CO2 adsorption is advantageous in that the waste material is being used to deal with another waste material, namely CO2. The waste materials utilised in this research were chitosan, a waste material derived from chitin, a large waste from the seafood industry, and polyvinylchloride (PVC), a polymer mainly used in the fabrication of household products. It is demonstrated in this thesis that with minimal modification, these waste materials can be utilised for the capture of CO2 at levels comparable to that of the currently available state-of-the-art materials.

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Sprague, Nicolle Marie. „Copper in the Urban Water Cycle: Sources and Sinks, Benefits and Detriments, and Corrosion in Soft Waters“. Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/42724.

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In recent years, stringent world-wide regulation of copper in drinking water, wastewater discharge and sludge has prompted utilities to carefully evaluate copper sources and sinks, benefits and detriments, and mitigation. This work compiled the individual efforts of researchers and utilities to provide a basis for holistic decision-making. Mass balances suggest that between 14-61% of copper in wastewater originates from home plumbing. Dosing of pure copper sulfate "root killer" by consumers, which is of unlikely value, accounted for up to 27% of copper inputs. Removal of copper in wastewater treatment ranged from 24-90%, suggesting a potential for optimization of these processes if desired. Finally, though utilities are pressured to reduce copper inputs at all stages of the urban water cycle, substantial benefits including human and wastewater bacteria micro-nutrition, water disinfection and algae control should not be overshadowed. To better understand copper inputs from corrosion in soft waters, a 12 month study was executed. Free chlorine (0.7 mg/L) was determined to have minimally adverse effects on copper release at pH 9.5 but no significant effect at pH 7.0, and higher temperatures usually increased copper release. Organic matter including soluble and particulate NOM, sodium alginate, and gum xanthan, tended to worsen copper release. Their direct effects included complexation and mobilization of pre-existing copper scale as particulates. Indirect effects were also discovered, including a propensity of gum xanthan and alginate to decrease pH, increasing copper release, and also to produce a microbiologically unstable water, decreasing the dissolved oxygen necessary for fueling corrosion reactions. The range of organic matter effects could be placed within a unified conceptual framework.
Master of Science

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Gandin, Anthony. „Rôle du métabolisme carboné dans la modulation de l'activité de la source et du puits chez l'érythrone d'amérique (Erythronium americanum)“. Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27042/27042.pdf.

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Dissertationen zum Thema „Carbon sinks or sources“

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