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  • Article  (16)
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  • 1
    Language: French
    In: Notes de Recherche de l'Académie d'Agriculture de France , ., 2015
    Description: Soils and associated agricultural activities are estimated to account for about 2/3 of the global emissions of nitrous oxide (N2O), a potent greenhouse gas. Soil water saturation is known to be a key factor for controlling N2O emissions. The aim of this study was to understand the controls linked to the soil hydric functioning on N2O emissions. Laboratory experiments were designed to control the hydric status of soil samples during wetting and drying cycles, and to measure simultaneously N2O fluxes (Figure 1). Three treatments of stepwise drying were performed across the range 0 to ı100 cm pressure head in two wetting–drying cycles. This experiment was reproduced for one soil sample during the acquisition of three-dimensional X-ray images. After image treatment, we could characterize the air-filled pore volume (Figures 3 and 4a) and gaseous connectivity (Figure 4b). Two types of N2O emission peaks were detected (Figure 2). A peak appeared within two or three days after rewetting and was related to microbial production processes and a slow N2O transport in water saturated soils. The second type of peak was detected within the first two steps of the decreasing pressure head, and occurred during a brief period, an average of 1.6 hour after the beginning of the soil drying. These peaks were induced by diffusion processes, and their intensities were correlated with the amount of water drained. Entrapment of N2O during the wetting phase and rapid displacement during the drying phase occurred. We highlighted the need to distinguish N2O production/consumption and transport phases to explain the variability of N2O emissions which is commonly measured.
    Description: Les sols et les activités agricoles qu’ils supportent contribueraient à environ 2/3 des émissions globales de protoxyde d’azote (N2O), un puissant gaz à effet de serre. L’objectif des travaux était la compréhension de l’influence de l’histoire hydrique des sols sur les émissions de N2O. Une expérimentation de laboratoire permettant un contrôle fin de l’état hydrique d’échantillons de sol durant des cycles de saturation et désaturation, ainsi que la mesure des flux de N2O, a été menée (Figure 1). Cette expérimentation a été reproduite pour un échantillon pendant l’acquisition simultanée d’images à l’aide d’un scanner médical à rayons X, ceci afin de caractériser le volume de pores libres à l’air (Figures 3 et 4a) et la connectivité gazeuse (Figure 4b). Deux types de pics d’émission de N2O, d’origine biologique et physique, ont été observés (Figure 2). Il a ainsi été mis en évidence la nécessité de distinguer les périodes de production/consommation de N2O de celles de son transport pour expliquer la variabilité des émissions de N2O couramment observées.
    Keywords: N2o ; Tomographie Aux Rayons X ; Saturation Du Sol ; Propriété Hydrique Du Sol ; Émission D'Azote ; Gaz À Effet De Serre ; Désaturation Du Sol ; Protoxyde D'Azote ; Milieux Et Changements Globaux ; État Hydrique
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 2
    Language: French
    In: Notes de Recherche de l'Académie d'Agriculture de France , ., 2015
    Description: Soils and associated agricultural activities are estimated to account for about 2/3 of the global emissions of nitrous oxide (N2O), a potent greenhouse gas. Soil water saturation is known to be a key factor for controlling N2O emissions. The aim of this study was to understand the controls linked to the soil hydric functioning on N2O emissions. Laboratory experiments were designed to control the hydric status of soil samples during wetting and drying cycles, and to measure simultaneously N2O fluxes (Figure 1). Three treatments of stepwise drying were performed across the range 0 to ı100 cm pressure head in two wetting–drying cycles. This experiment was reproduced for one soil sample during the acquisition of three-dimensional X-ray images. After image treatment, we could characterize the air-filled pore volume (Figures 3 and 4a) and gaseous connectivity (Figure 4b). Two types of N2O emission peaks were detected (Figure 2). A peak appeared within two or three days after rewetting and was related to microbial production processes and a slow N2O transport in water saturated soils. The second type of peak was detected within the first two steps of the decreasing pressure head, and occurred during a brief period, an average of 1.6 hour after the beginning of the soil drying. These peaks were induced by diffusion processes, and their intensities were correlated with the amount of water drained. Entrapment of N2O during the wetting phase and rapid displacement during the drying phase occurred. We highlighted the need to distinguish N2O production/consumption and transport phases to explain the variability of N2O emissions which is commonly measured.
    Description: Les sols et les activités agricoles qu’ils supportent contribueraient à environ 2/3 des émissions globales de protoxyde d’azote (N2O), un puissant gaz à effet de serre. L’objectif des travaux était la compréhension de l’influence de l’histoire hydrique des sols sur les émissions de N2O. Une expérimentation de laboratoire permettant un contrôle fin de l’état hydrique d’échantillons de sol durant des cycles de saturation et désaturation, ainsi que la mesure des flux de N2O, a été menée (Figure 1). Cette expérimentation a été reproduite pour un échantillon pendant l’acquisition simultanée d’images à l’aide d’un scanner médical à rayons X, ceci afin de caractériser le volume de pores libres à l’air (Figures 3 et 4a) et la connectivité gazeuse (Figure 4b). Deux types de pics d’émission de N2O, d’origine biologique et physique, ont été observés (Figure 2). Il a ainsi été mis en évidence la nécessité de distinguer les périodes de production/consommation de N2O de celles de son transport pour expliquer la variabilité des émissions de N2O couramment observées.
    Keywords: N2o ; Tomographie Aux Rayons X ; Saturation Du Sol ; Propriété Hydrique Du Sol ; Émission D'Azote ; Gaz À Effet De Serre ; Désaturation Du Sol ; Protoxyde D'Azote ; Milieux Et Changements Globaux ; État Hydrique
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 3
    Language: French
    In: Biogeochemistry 2-3 , 395-408., 2015
    Description: Nitrous oxide (N2O) fluxes can increase significantly following small increases in soil water-filled pore space (WFPS). Thus, it is essential to improve our knowledge of this crucial relationship to better model N2O emissions by soils. We studied how much the addition of a gas transport and a gas–liquid equilibrium module to the model of N2O emissions NOE could improve simulation results. A sensitivity analysis of the modified model (NOEGTE: gas transport and equilibrium) was first performed, and then the model was tested with published data of a wetting–drying experiment. Simulated N2O fluxes plotted against WFPS appeared to be bell-shaped during the 7 days simulated, combining the effects of the low N2O production for WFPS 0.95. The WFPS generating the maximum simulated N2O fluxes shifted with time, from 0.76 after 12 h, to 0.79 after 168 h, because of an increase over time of the gas concentration gradient between the soil surface and the atmosphere. NOEGTE appeared able to capture the pattern of N2O emissions monitored in the experimental data. In particular, N2O peaks during drying were well reproduced in terms of timing, but their magnitudes were often overestimated. They were attributed to the increasing gas diffusivity and N2O exchanges from the liquid phase to the gaseous phase.
    Keywords: Modélisation ; Nitrous Oxide Emission Modeling;Water-Filled Pore Space;Gas Diffusivity;Soil ; Indice D'Eau ; Espace Poral ; Sciences De La Terre ; Earth Sciences ; Flux D'Azote ; Émission D'Azote ; Transport De L'Azote ; Protoxyde D'Azote ; Porosité Saturée En Eau
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 4
    Language: French
    In: Biogeochemistry 2-3 , 395-408., 2015
    Description: Nitrous oxide (N2O) fluxes can increase significantly following small increases in soil water-filled pore space (WFPS). Thus, it is essential to improve our knowledge of this crucial relationship to better model N2O emissions by soils. We studied how much the addition of a gas transport and a gas–liquid equilibrium module to the model of N2O emissions NOE could improve simulation results. A sensitivity analysis of the modified model (NOEGTE: gas transport and equilibrium) was first performed, and then the model was tested with published data of a wetting–drying experiment. Simulated N2O fluxes plotted against WFPS appeared to be bell-shaped during the 7 days simulated, combining the effects of the low N2O production for WFPS 0.95. The WFPS generating the maximum simulated N2O fluxes shifted with time, from 0.76 after 12 h, to 0.79 after 168 h, because of an increase over time of the gas concentration gradient between the soil surface and the atmosphere. NOEGTE appeared able to capture the pattern of N2O emissions monitored in the experimental data. In particular, N2O peaks during drying were well reproduced in terms of timing, but their magnitudes were often overestimated. They were attributed to the increasing gas diffusivity and N2O exchanges from the liquid phase to the gaseous phase.
    Keywords: Modélisation ; Nitrous Oxide Emission Modeling;Water-Filled Pore Space;Gas Diffusivity;Soil ; Indice D'Eau ; Espace Poral ; Sciences De La Terre ; Earth Sciences ; Flux D'Azote ; Émission D'Azote ; Transport De L'Azote ; Protoxyde D'Azote ; Porosité Saturée En Eau
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 5
    Language: English
    In: Vadose Zone Journal, 2015, Vol.14(8)
    Description: Water in soil is known to be a key factor for controlling N2O emissionsbecause N2O is mainly produced by denitrification in anoxic environments.In this study, we proposed a methodology to image the water and soil structureof a soil sample with X-ray computed tomography while controlling...
    Keywords: Sciences of the Universe ; Sciences of the Universe ; Continental Interfaces, Environment ; Soil ; Nitrous Oxide ; X-Ray Computed Tomography ; Gas Diffusivity ; Pore Connectivity ; Agriculture
    E-ISSN: 1539-1663
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  • 6
    Language: English
    In: Applied Physics A, 2016, Vol.122(11), pp.1-9
    Description: Building stones are frequently subjected to very intense degradation due to salt crystallization, often responsible for strong modifications of their pore network. These effects have a great influence on the mechanical properties and durability of the materials, and on the penetration of water. Therefore, the quantification and visualization of water absorption into the pore network of degraded stones could provide useful information to better understand the weathering process. In this study, neutron radiography has been used (1) to monitor and visualize in two dimensions the capillary water uptake in a Sicilian calcarenite widely used as building and replace stone (namely Sabucina stone) and (2) to quantify the water content distribution, as a function of time and weathering degree. Additionally, traditional experiments based on gravimetric methods have been performed, following the standard recommendations. Results demonstrated a change in the physical properties of Sabucina stones with the intensification of the degradation process, with severe effects on the capillary imbibition dynamics. The water penetration depth at the end of the experiment was substantially higher in the fresh than in the weathered stones. The water absorption kinetics was faster in the weathered samples, and the amount of water absorbed increased with the number of weathering cycles. Good agreement between classical and neutron imaging data has also been evidenced. However, neutron radiography has allowed retrieving additional spatial information on the water absorption process, and to better understand how salt weathering affects the petrophysical properties of the studied stone and how it influences then the stone response against water.
    Keywords: Green Buildings ; Diagnostic Imaging;
    ISSN: 0947-8396
    E-ISSN: 1432-0630
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  • 7
    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)
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  • 8
    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)
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  • 9
    Language: French
    In: Sud-Ouest européen, 01 June 2012, pp.11-24
    Description: Dans les zones urbaines et périurbaines, les sols sont soumis à de fortes pressions pour être construits sans faire pour autant l’objet d’évaluation de leurs autres fonctionnalités ou de leurs potentialités. Le projet UQualiSol-ZU a pour objectif d’évaluer dans quelle mesure et comment les connaissances scientifiques sur les sols pourraient être intégrées dans les documents d’urbanisme. Il s’agit : 1) d’établir un diagnostic de territoire en termes de consommation de terres par l’urbanisation et de prise en compte des sols par les urbanistes ; 2) d’analyser les outils réglementaires afin d’identifier comment la qualité du sol pourrait y être intégrée ; 3) d’identifier quelles connaissances sur les sols seraient utilisables par les urbanistes et de proposer un indice d’adéquation d’usage des sols basé sur la multifonctionnalité des sols. Cette approche est testée sur deux communes de la région Aix-Marseille.
    Keywords: Land Planning ; Soil Quality ; Regulation ; Index ; Urban Planning ; Qualité Du Sol ; Planification ; Urbanisme ; Indice ; Réglementation ; Calidad Del Suelo ; Planificación ; Urbanismo ; Índice ; Reglamentación ; Geography ; History & Archaeology
    ISSN: 1276-4930
    E-ISSN: 2273-0257
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  • 10
    Language: English
    In: SOIL, 2018, Vol.4(1), pp.83-92
    Description: The central importance of soil for the functioning of terrestrial systems is increasingly recognized. Critically relevant for water quality, climate control, nutrient cycling and biodiversity, soil provides more functions than just the basis for agricultural production. Nowadays, soil is increasingly under pressure as a limited resource for the production of food, energy and raw materials. This has led to an increasing demand for concepts assessing soil functions so that they can be adequately considered in decision-making aimed at sustainable soil management. The various soil science disciplines have progressively developed highly sophisticated methods to explore the multitude of physical, chemical and biological processes in soil. It is not obvious, however, how the steadily improving insight into soil processes may contribute to the evaluation of soil functions. Here, we present to a new systemic modeling framework that allows for a consistent coupling between reductionist yet observable indicators for soil functions with detailed process understanding. It is based on the mechanistic relationships between soil functional attributes, each explained by a network of interacting processes as derived from scientific evidence. The non-linear character of these interactions produces stability and resilience of soil with respect to functional characteristics. We anticipate that this new conceptional framework will integrate the various soil science disciplines and help identify important future research questions at the interface between disciplines. It allows the overwhelming complexity of soil systems to be adequately coped with and paves the way for steadily improving our capability to assess soil functions based on scientific understanding.
    Keywords: Soil Stability ; Evaluation ; Agricultural Production ; Modelling ; Agricultural Management ; Biodiversity ; Soil Stability ; Food Production ; Water Quality ; Raw Materials ; Biological Activity ; Decision Making ; Soil Improvement ; Soil Science ; Terrestrial Environments ; Interactions ; Water Quality ; Soil Management ; Modelling ; Raw Materials ; Raw Materials ; Soil Sciences ; Water Quality ; Soils ; Framework ; Stability ; Nutrient Cycles ; Mathematical Models ; Agricultural Production ; Biodiversity ; Nutrients (Mineral) ; Soils ; Decision Making ; Water Quality ; Biodiversity ; Biodiversity;
    ISSN: SOIL
    E-ISSN: 2199-398X
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