O ciclo diurno do fluxo de CO2 no oceano Atlântico equatorial para o mês de agosto é estimado utilizando um algoritmo de transferência de gases. O algoritmo é baseado na teoria de similaridade de Monin-Obukhov para fluxos turbulentos na interface ar-mar e na física da transferência de CO2 na camada molecular oceânica. O ciclo diurno do fluxo de CO2, obtido na região, caracteriza o oceano Atlântico equatorial, durante o período, como fonte de CO2 para a atmosfera e seus valores estão entre 0,71 e 0,85 mol CO2 m^-2 ano^-1. / The diurnal cycle of CO2 is estimated for the month of August on the Atlantic Ocean using a gas transfer algorithm. The algorithm is based on the Monin-Obukhov similarity theory for turbulent transfer at the air-sea interface and the physics of the CO2 transfer at the oceanic molecular layer.

La respiration du sol (Rs) en milieu forestier est influencée par les conditions hydroclimatiques du sol ainsi que par la composition en espèces et la qualité de la litière. La hausse des températures et les changements dans les patrons de précipitation, attendus en contexte de changements climatiques, ont donc un fort potentiel de modifier Rs et ainsi, la concentration de CO2 atmosphérique. En ce sens, ce projet de recherche visait tout d’abord à étudier l’effet d’un réchauffement et d’un assèchement artificiels des sols sur Rs, puis à évaluer si la réponse des sols au chauffage allait varier selon le type de couvert forestier. Nous avons échantillonné le flux gazeux des sols sur deux ans dans trois peuplements d'une forêt tempérée décidue à sa limite nordique. Les résultats ont démontré une faible accentuation de Rs en réponse au chauffage, mais seulement jusqu’à un seuil de température du sol d’environ 15°C à partir duquel l’effet positif du chauffage s’estompe, voire s’inverse. Cependant, cette tendance n’était pas systématique puisque les trois peuplements ont démontré une sensibilité différente au chauffage, l’érablière à hêtre étant beaucoup plus sensible que la forêt mixte et l’érablière à bouleau. Ce qui était toutefois commun aux trois peuplements, c’est l’affaiblissement de l’influence de la température sur Rs passé le seuil de 15°C. Outre la température du sol, l’intégration d’autres variables, comme la teneur en eau, l’activité ionique en N, P et Ca de la solution de sol et la présence de conifères au modèle cherchant à expliquer la variabilité de Rs, n’a pas augmenté la puissance explicative du modèle, et ce pour aucun des traitements ou des peuplements. Les résultats de cette étude suggèrent néanmoins un élément intéressant, soit le plafonnement potentiel de Rs malgré la hausse des températures. Ceci apporte un questionnement quant à la magnitude de la rétroaction positive entre le cycle du carbone terrestre et le système climatique. / Forest soil respiration (Rs) is driven by soil hydroclimatic conditions as well as species composition and litter quality. Rising temperatures and changes in precipitation patterns, expected in the context of climate change, therefore have a strong potential to modify Rs and thus the concentration of atmospheric CO2. This research aimed to study the effect of artificial heating and drying of soils on Rs, and to assess whether the response of soils to heating would vary according to the type of forest cover. We sampled soil gas flux over two years in three stands of a temperate deciduous forest at its northern edge. The results demonstrated a weak accentuation of Rs in response to heating, but only up to a soil temperature threshold of about 15°C, where the positive heating effect decreases or is even reversed. However, this trend was not systematic since the three stands demonstrated a different sensitivity to heating, the maple-beech forest being much more sensitive than the mixed forest and the maple-birch forest. Yet, what was common to the three stands was the decrease of the influence of temperature on Rs above the threshold of 15°C. In addition to soil temperature, the integration of other variables, such as water content, ionic activity in N, P and Ca of the soil solution and the presence of conifers in the model seeking to explain the variability of Rs, did not increase the explanatory power of the model for any of the treatments or stands. The results of this study highlight a potential capping of Rs despite the increase in temperatures. They bring questions regarding the magnitude of the positive feedback between the terrestrial carbon cycle and the climate system.

Cette thèse constitue une étude de référence sur la qualité des ressources hydriques du bassin versant du fleuve Ibrahim au Liban, notamment avant la construction d’un grand barrage (Jannah). Pour ce faire, 7 stations (NI7 à NI1) ont été sélectionnées de l’amont vers l’aval sur l’Ibrahim et ses sources karstiques. L’ensemble des sept sous bassins a été caractérisé d’un point de vue hydroclimatologie et états de surface (sols, végétation, cultures, géologie, relief). Les débits mesurés à l’amont (2 stations) et à l’aval (1 station) nous ont permis de reconstituer les débits des autres stations intermédiaires grâce à des relations débits-surfaces spécifiques. À partir de prélèvements et d’analyses chimiques de la composition des eaux tout au long d’un cycle hydrologique et avec une fréquence mensuelle, les flux de matières exportées en solution par l’Ibrahim ont été estimés à 122 372 t/an. 80% de ce tonnage est exporté durant la période des hautes eaux. À partir de ce tonnage, on a pu estimer que l’altération chimique des roches carbonatées sur l’ensemble du bassin s’effectue à la vitesse de 81 cm/10000 ans. Cette altération consomme un flux élevé de CO2 typique des régions carbonatées soumises à un drainage intense (1500 mm/an), soit 2,23 x106 moles/km2/an de CO2. L’analyse de la concentration en éléments traces dans les sédiments de fond des cours d’eau, intégrateurs des transports solides, en hautes eaux et en basses eaux, montre des concentrations élevées pour le Sc, V, Cr, Co, Ni, Ga et Cu en passant de NI5 jusqu’à NI2. L’évaluation du degré de cette contamination et de sa variation spatio-temporelle a été effectuée grâce au facteur d’enrichissement en normalisant par rapport à l’aluminium et en prenant les sédiments de la station amont NI7 (source karstique) considérés comme peu ou pas contaminés en ET, comme fond géochimique naturel. Des teneurs élevées en Zn, Pb, Cu et d’autres éléments traces montrent que dans cette région où les activités industrielles, agricoles, et urbaines sont développées, il existe un apport anthropique non négligeable en éléments métalliques. Mais cette contamination reste modérée / Throughout the study framework conducted on the quality of the water resources in the Ibrahim River watershed in Lebanon (notably before the construction of a large dam, Jannah), 7 stations (NI7 to NI1) were selected, from upstream to downstream, including its karst springs. Hydroclimatological and specific catchment characteristics (such as land cover use, geology, hydrology, soil and topography) where characterized for the whole seven sub-basins respectively. Discharge data from the sources (2 stations) and the basin outlet (1 station) enhanced our study to determine and further calculate the discharge of other stations. Sampling and analyzing the chemical composition of water collected monthly during one hydrological cycle allowed us to determine the amount of dissolved material carried by the Ibrahim River. The river flux of dissolved material was estimated at 122 372 tons / year of which 80% of is exported during high flow season. Therefore this flux allowed us to estimate the rate of chemical weathering of carbonate rocks across the basin at 81 cm / 10000 years. This alteration consumes a high flux of CO2 (around 2,23x106 moles/km2/year of CO2) typical for carbonate regions subject to intense drainage (1500 mm). The analysis for the concentration of trace elements in fluvial sediments for the Ibrahim River for the low and high flow periods shows high concentrations of Sc, V, Cr, Co, Ni, Cu and Ga in the from NI5 station up to NI2. The assessment of the extent of the contamination and its spatio-temporal variation was conducted using the enrichment factor by normalizing to aluminium concentration and using the element concentrations in the sediments of station NI7 (karstic sspring) considered as the natural geochemical background for this catchment. High levels of Zn, Pb, Cu and other traces of noticeable elements show that in this region where industrial, agricultural and urban activities are developed, there is a significant anthropogenic contribution for some metallic elements; thus the trace element contamination remains moderate.

Böden sind Quelle und Senke für klimarelevante Spurengase (CO2, CH4 und N2O). Die freigesetzten Mengen sind mit denen aus Verbrennung fossiler Rohstoffe vergleichbar und können diese übersteigen, sodass Böden das Klima beeinflussen. Die wichtigsten Einflussgrößen der Bodenentgasung sind Vegetation, Bodenbearbeitung, Bodenfeuchte und Bodentemperatur. In dieser Arbeit wurden CO2-Flüsse für Acker-, Grünland- und Waldböden in Sachsen ganzjährig erfasst und eine Regionalisierung für die Landesfläche durchgeführt. Die Methodik umfasste flächendeckende Kurzeitfeldmessungen, punktuelle Langzeitfeldmessungen sowie gezielte Laborversuche. Zur Realisierung wurden robuste, transportable und präzise Kammersysteme zur manuellen und automatisierten Messung der Bodenentgasung im Freiland und Labor entwickelt. Für die Berechnung der Ökosystematmung aus den Messwerten konnte eine empirische Formel erstellt werden. Aus den Analyseergebnissen wurde raumzeitlich strukturiertes Kartenmaterial für die Ökosystematmung im Freistaat Sachsen in den verschiedenen Ökosystemen erstellt.:1 Einleitung 2 Aktueller Wissensstand 2.1 Bedeutung der Thematik 2.2 Treibhausgasemissionen 2.3 Entstehung von Treibhausgasen im Boden 2.4 Einflussgrößen auf die Bodenentgasung 2.5 Messmethoden 2.6 Methodenvergleich 3 Entwicklung von Probenahmesystemen 3.1 Manuelles System 3.2 Automatisierte Systeme 3.3 Berechnungsmethode 4 Versuchsdurchführung 4.1 Auswahl der Messstandorte 4.2 Untersuchungsgebiet 4.3 Meteorologische Daten 4.4 Experimentalarbeiten 4.5 Hochrechnung der Punktmessungen auf die Fläche 4.6 Fehlerbetrachtung 5 Ergebnisse und Diskussion 5.1 Labormessungen in der Klimakammer 5.2 Freilandmessungen – landwirtschaftliche Flächen 2012 5.3 Dauermessung mit SEACH-FG in Hilbersdorf 5.4 Pilotmessungen auf teilversiegelten Flächen und Stadtböden 5.5 Empirische Formel zur Ermittlung der Ökosystematmung 5.6 Hochrechnung der Bodenentgasung für Sachsen 5.7 Ökosystematmung der Bodengroßlandschaften 5.8 Ökosystematmung verschiedener Höhenlagen 6 Entwurf eines Monitoringkonzepts für Sachsen 7 Ausblick 8 Zusammenfassung

Surface manifestations of hydrothermal fluids such as fumaroles and hot springs provide valuable information about the level of activity of a volcano during quiescent period. Geochemical study of gas and spring waters is useful to elaborate geochemical model for magmatic-hydrothermal system. Furthermore, temporal geochemical monitoring of these fluids with time provides a better understanding in processes occurring inside the volcano and can be useful to detect any changes in the activity of the magmatic-hydrothermal system. This thesis investigates two hydrothermal systems at Kelud and Papandayan volcanoes that are located at Java Island in Indonesia. Kelud is considered as one of the most dangerous volcanoes of Java because of its frequent eruptions. After the last eruption that occurred in 1990, a new lake rapidly filled the crater of Kelud volcano. Water samples collected since 1993 are near neutral Na-K chloride fluids and are typical of aged hydrothermal system where the acidity has been completely neutralized by fluid-rock interaction and where the emission of acid magmatic gases has stopped. Two sudden increases in lake temperature in 1996 and 2001 were accompanied by rapid changes in lake water compositions and suggest the existence of two hydrothermal systems feeding the lake: a shallow hydrothermal system dominated by Ca-Mg sulfate waters and a deepest aquifer with neutral alkali chloride waters. From 2001 to 2005, measurements of CO2 emitted by the surface of the lake were performed by using the accumulation chamber method modified in order to work at the surface of a crater lake. Two statistical methods were used to process data: the graphical statistical and stochastic simulation methods. The results of graphical statistical approach showed that two different degassing processes are acting at the lake surface: one corresponding to CO2 fluxes resulting from rising bubbles and the other corresponding to equilibrium diffusion of dissolved CO2 at the water-air surface. Total CO2 emission rate estimated by stochastic simulation ranges from 105 t/day for 2001 to 32 t/day for 2005. Thermal energy released by the lake was also estimated by using an energy balance model with a new constraint using the CO2 flux. The thermal flux decreased from 200 MW (2001) to 100 MW (2002) and then remained stable. Correlation between the chemical data of waters, the fluxes of CO2 and energy show that a constant decrease in the level of activity of the volcano since 1993 occurred although the lake temperature has been stable since 2003. Since the last magmatic eruption that occurred in 1772, phreatic eruptions occur on Papandayan volcano with the last one in 2002. The volcanic material ejected during this eruption is essentially made of altered rocks from within the hydrothermal system. The interaction of acid waters with the host rocks corresponds to an advanced argilic alteration. The chemical compositions of waters from Papandayan volcano and Kelud lake waters are contrasting. Indeed, the spring waters sampled since 1994 are acid sulfate-chloride waters and acid sulfate waters. The chemical and isotopic analyses of gases and waters suggest a significant magmatic contribution in SO2, HCl and HF to the hydrothermal system. The chemical composition of waters sampled after the 2002 eruption have provided information about origin of this eruption. Decrease in chloride concentration and in delta 34S of dissolved sulfates showed that the magmatic contribution in these fluids are less important and that the waters are likely to be formed by the condensation of steam (H2O, H2S) rising from a boiling aquifer.

Surface manifestations of hydrothermal fluids such as fumaroles and hot springs provide valuable information about the level of activity of a volcano during quiescent period. Geochemical study of gas and spring waters is useful to elaborate geochemical model for magmatic-hydrothermal system. Furthermore, temporal geochemical monitoring of these fluids with time provides a better understanding in processes occurring inside the volcano and can be useful to detect any changes in the activity of the magmatic-hydrothermal system. This thesis investigates two hydrothermal systems at Kelud and Papandayan volcanoes that are located at Java Island in Indonesia. Kelud is considered as one of the most dangerous volcanoes of Java because of its frequent eruptions. After the last eruption that occurred in 1990, a new lake rapidly filled the crater of Kelud volcano. Water samples collected since 1993 are near neutral Na-K chloride fluids and are typical of aged hydrothermal system where the acidity has been completely neutralized by fluid-rock interaction and where the emission of acid magmatic gases has stopped. Two sudden increases in lake temperature in 1996 and 2001 were accompanied by rapid changes in lake water compositions and suggest the existence of two hydrothermal systems feeding the lake: a shallow hydrothermal system dominated by Ca-Mg sulfate waters and a deepest aquifer with neutral alkali chloride waters. From 2001 to 2005, measurements of CO2 emitted by the surface of the lake were performed by using the accumulation chamber method modified in order to work at the surface of a crater lake. Two statistical methods were used to process data: the graphical statistical and stochastic simulation methods. The results of graphical statistical approach showed that two different degassing processes are acting at the lake surface: one corresponding to CO2 fluxes resulting from rising bubbles and the other corresponding to equilibrium diffusion of dissolved CO2 at the water-air surface. Total CO2 emission rate estimated by stochastic simulation ranges from 105 t/day for 2001 to 32 t/day for 2005. Thermal energy released by the lake was also estimated by using an energy balance model with a new constraint using the CO2 flux. The thermal flux decreased from 200 MW (2001) to 100 MW (2002) and then remained stable. Correlation between the chemical data of waters, the fluxes of CO2 and energy show that a constant decrease in the level of activity of the volcano since 1993 occurred although the lake temperature has been stable since 2003. Since the last magmatic eruption that occurred in 1772, phreatic eruptions occur on Papandayan volcano with the last one in 2002. The volcanic material ejected during this eruption is essentially made of altered rocks from within the hydrothermal system. The interaction of acid waters with the host rocks corresponds to an advanced argilic alteration. The chemical compositions of waters from Papandayan volcano and Kelud lake waters are contrasting. Indeed, the spring waters sampled since 1994 are acid sulfate-chloride waters and acid sulfate waters. The chemical and isotopic analyses of gases and waters suggest a significant magmatic contribution in SO2, HCl and HF to the hydrothermal system. The chemical composition of waters sampled after the 2002 eruption have provided information about origin of this eruption. Decrease in chloride concentration and in delta 34S of dissolved sulfates showed that the magmatic contribution in these fluids are less important and that the waters are likely to be formed by the condensation of steam (H2O, H2S) rising from a boiling aquifer.<p><p> / Doctorat en sciences, Spécialisation géologie / info:eu-repo/semantics/nonPublished