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Berlin Brandenburg

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  • 1
    Language: French
    Description: Les sols et les activités agricoles qu’ils supportent, contribueraient à environ 2/3 des émissionsglobales de protoxyde d’azote (N2O), un puissant gaz à effet de serre. L’objectif de la thèseétait la compréhension des déterminismes des émissions de N2O liés aux propriétés hydriques dessols. Des expérimentations de laboratoire permettant le contrôle hydrique fin d’échantillons de sol,en saturation et en désaturation, et la mesure des flux de N2O ont été menées. Un couplage avecla tomographie par rayons-X a par ailleurs permis de caractériser la connectivité gazeuse. Enfin,une démarche de modélisation a permis de tester les hypothèses de fonctionnement émises, etde poursuivre la démarche de réflexion sur le lien entre les propriétés hydriques des sols et lesémissions de N2O. On a mis en évidence le rôle des propriétés hydriques des sols dans la variabilitédes émissions de N2O couramment observées, et la nécessité de distinguer des périodes deproduction/consommation de N2O et de transport. On retiendra ainsi le fort caractère dynamique desémissions de N2O, en lien avec la phase hydrique (saturation ou désaturation), le fonctionnementhydrodynamique des sols, le transport gazeux et la configuration spatiale de l’air et de l’eau dansle réseau de pores. Afin de décrire l’intensité et le timing des pics de N2O, il est apparu pertinentd’observer les paramètres potentiel matriciel, coefficient de diffusion gazeuse et connectivité gazeuse,en plus de la teneur en eau. Ces observations ont des implications sur la modélisation des flux deN2O. On recommande ainsi l’utilisation couplée de modules de transport hydrique, de transportgazeux et en solution de N2O, en plus de modules de production microbiologique, pour prédireefficacement les émissions de N2O.
    Description: Soils and associated agricultural activities are estimated to account for about 2/3 of theglobal emissions of nitrous oxide (N2O), a potent greenhouse gas. The aim of the thesis was tounderstand the controls linked to soil hydric properties on N2O emissions. Laboratory experimentswere designed to control the hydric status of soil samples during wetting and drying, and to measureN2O fluxes. Moreover, a coupling with X-ray computed tomography allowed characterizing thegaseous connectivity. Finally, a modeling approach allowed testing the hypotheses of functioning,and to further discuss the links between hydric properties and N2O emissions. We highlighted therole of soil hydric properties on the variability of N2O emissions which is often measured, and theneed to distinguish N2O production/consumption and transport phases. The highly dynamic nature ofN2O emissions was linked to the hydric phase (wetting or drying), soil hydrodynamic functioning, gastransport, and spatial configuration of water and air in the pore network, in addition to the water-filledpore space parameter. These observations have implications for N2O emission modeling. Werecommend thus the coupled use of hydric transport, and modules of gas and liquid transport of N2O,in addition to microbial production modules to efficiently predict N2O emissions.
    Keywords: Transport Gazeux ; N2o ; Hysteresis ; Earth Sciences ; Propriété Hydrique Du Sol ; Flux Hydrique ; Émission D'Azote ; Espace Poral ; Sciences De La Terre ; Flux D'Azote ; Gaz À Effet De Serre ; Fonctionnement Hydrique ; Protoxyde D'Azote ; Teneur En Eau ; Nitrous Oxide;Soil;Water-Filled Pore Space;Gas Transport;Hydric Fluxes;Soil Water Hysteresis ; Porosité Saturée En Eau
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: French
    Description: Les sols et les activités agricoles qu’ils supportent, contribueraient à environ 2/3 des émissionsglobales de protoxyde d’azote (N2O), un puissant gaz à effet de serre. L’objectif de la thèseétait la compréhension des déterminismes des émissions de N2O liés aux propriétés hydriques dessols. Des expérimentations de laboratoire permettant le contrôle hydrique fin d’échantillons de sol,en saturation et en désaturation, et la mesure des flux de N2O ont été menées. Un couplage avecla tomographie par rayons-X a par ailleurs permis de caractériser la connectivité gazeuse. Enfin,une démarche de modélisation a permis de tester les hypothèses de fonctionnement émises, etde poursuivre la démarche de réflexion sur le lien entre les propriétés hydriques des sols et lesémissions de N2O. On a mis en évidence le rôle des propriétés hydriques des sols dans la variabilitédes émissions de N2O couramment observées, et la nécessité de distinguer des périodes deproduction/consommation de N2O et de transport. On retiendra ainsi le fort caractère dynamique desémissions de N2O, en lien avec la phase hydrique (saturation ou désaturation), le fonctionnementhydrodynamique des sols, le transport gazeux et la configuration spatiale de l’air et de l’eau dansle réseau de pores. Afin de décrire l’intensité et le timing des pics de N2O, il est apparu pertinentd’observer les paramètres potentiel matriciel, coefficient de diffusion gazeuse et connectivité gazeuse,en plus de la teneur en eau. Ces observations ont des implications sur la modélisation des flux deN2O. On recommande ainsi l’utilisation couplée de modules de transport hydrique, de transportgazeux et en solution de N2O, en plus de modules de production microbiologique, pour prédireefficacement les émissions de N2O.
    Description: Soils and associated agricultural activities are estimated to account for about 2/3 of theglobal emissions of nitrous oxide (N2O), a potent greenhouse gas. The aim of the thesis was tounderstand the controls linked to soil hydric properties on N2O emissions. Laboratory experimentswere designed to control the hydric status of soil samples during wetting and drying, and to measureN2O fluxes. Moreover, a coupling with X-ray computed tomography allowed characterizing thegaseous connectivity. Finally, a modeling approach allowed testing the hypotheses of functioning,and to further discuss the links between hydric properties and N2O emissions. We highlighted therole of soil hydric properties on the variability of N2O emissions which is often measured, and theneed to distinguish N2O production/consumption and transport phases. The highly dynamic nature ofN2O emissions was linked to the hydric phase (wetting or drying), soil hydrodynamic functioning, gastransport, and spatial configuration of water and air in the pore network, in addition to the water-filledpore space parameter. These observations have implications for N2O emission modeling. Werecommend thus the coupled use of hydric transport, and modules of gas and liquid transport of N2O,in addition to microbial production modules to efficiently predict N2O emissions.
    Keywords: Transport Gazeux ; N2o ; Hysteresis ; Earth Sciences ; Propriété Hydrique Du Sol ; Flux Hydrique ; Émission D'Azote ; Espace Poral ; Sciences De La Terre ; Flux D'Azote ; Gaz À Effet De Serre ; Fonctionnement Hydrique ; Protoxyde D'Azote ; Teneur En Eau ; Nitrous Oxide;Soil;Water-Filled Pore Space;Gas Transport;Hydric Fluxes;Soil Water Hysteresis ; Porosité Saturée En Eau
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Vadose Zone Journal 8 , ., 2015
    Description: Water in soil is known to be a key factor for controlling N2O emissions because N2O is mainly produced by denitrification in anoxic environments. In this study, we proposed a methodology to image the water and soil structure of a soil sample with X-ray computed tomography while controlling the hydric state and monitoring N2O fluxes. We used a multistep outflow system to apply two wetting–drying cycles to an undisturbed soil. The soil core was scanned with coarse-resolution X-ray computed tomography, one time during wetting and several times during drying, to measure quantitative and qualitative indicators of the pore network. Nitrous oxide emissions were higher during the first (C1) than during the second (C2) wetting–drying cycle for both the wetting and the drying phases. Fluxes increased quickly after the beginning of the drying phase to reach a peak after 5 h. Differences in the intensity of N2O emissions between the two cycles were attributed to differences in the water saturation, air-phase connectivity, and relative gas diffusion coefficient, which led to more or less N2O production, consumption, and entrapment in the soil. The speed of the N2O emissions at the beginning of the drying phase depended on the rate of increase of the air-filled pore volume and connectivity, and was especially well described by the estimated relative gas diffusion coefficient. Parameters of the soil structure were not able to explain completely the intensity of N2O emissions during drying; N2O production and consumption factors were also involved.
    Keywords: N2o ; Earth Sciences ; Flux Hydrique ; Structure Du Sol ; Émission De Gaz ; Modélisation ; Eau Du Sol ; Flux De Gaz ; Tomographie Aux Rayons X ; Sciences De La Terre ; Alternance Humectation Dessication ; Protoxyde D'Azote ; Milieux Et Changements Globaux ; État Hydrique
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Vadose Zone Journal 8 , ., 2015
    Description: Water in soil is known to be a key factor for controlling N2O emissions because N2O is mainly produced by denitrification in anoxic environments. In this study, we proposed a methodology to image the water and soil structure of a soil sample with X-ray computed tomography while controlling the hydric state and monitoring N2O fluxes. We used a multistep outflow system to apply two wetting–drying cycles to an undisturbed soil. The soil core was scanned with coarse-resolution X-ray computed tomography, one time during wetting and several times during drying, to measure quantitative and qualitative indicators of the pore network. Nitrous oxide emissions were higher during the first (C1) than during the second (C2) wetting–drying cycle for both the wetting and the drying phases. Fluxes increased quickly after the beginning of the drying phase to reach a peak after 5 h. Differences in the intensity of N2O emissions between the two cycles were attributed to differences in the water saturation, air-phase connectivity, and relative gas diffusion coefficient, which led to more or less N2O production, consumption, and entrapment in the soil. The speed of the N2O emissions at the beginning of the drying phase depended on the rate of increase of the air-filled pore volume and connectivity, and was especially well described by the estimated relative gas diffusion coefficient. Parameters of the soil structure were not able to explain completely the intensity of N2O emissions during drying; N2O production and consumption factors were also involved.
    Keywords: N2o ; Earth Sciences ; Flux Hydrique ; Structure Du Sol ; Émission De Gaz ; Modélisation ; Eau Du Sol ; Flux De Gaz ; Tomographie Aux Rayons X ; Sciences De La Terre ; Alternance Humectation Dessication ; Protoxyde D'Azote ; Milieux Et Changements Globaux ; État Hydrique
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
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