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  • 2014  (32)
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  • 2014  (32)
  • 1
    Language: English
    In: Transport in Porous Media, 2014, Vol.105(2), pp.391-410
    Description: Numerical models that solve transport of pollutants at the macroscopic scale in unsaturated porous media need the effective diffusion dependence on saturation as an input. We conducted numerical computations at the pore scale in order to obtain the effective diffusion curve as a function of saturation for an academic sphere packing porous medium and for a real porous medium where pore structure knowledge was obtained through X-ray tomography. The computations were performed using a combination of lattice Boltzmann models based on two relaxation time (TRT) scheme. The first stage of the calculations consisted in recovering the water spatial distribution into the pore structure for several fixed saturations using a phase separation TRT lattice Boltzmann model. Then, we performed diffusion computation of a non-reactive solute in the connected water structure using a diffusion TRT lattice Boltzmann model. Finally, the effective diffusion for each selected saturation value was estimated through inversion of a macroscopic classical analytical solution.
    Keywords: Lattice Boltzmann method ; Effective diffusion ; TRT ; Unsaturated ; Porous media
    ISSN: 0169-3913
    E-ISSN: 1573-1634
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  • 2
    Language: English
    In: Science of the Total Environment, 15 November 2014, Vol.499, pp.546-559
    Description: Transport processes in soils are strongly affected by heterogeneity of soil hydraulic properties. Tillage practices and compost amendments can modify soil structure and create heterogeneity at the local scale within agricultural fields. The long-term field experiment QualiAgro (INRA–Veolia partnership 1998–2013) explores the impact of heterogeneity in soil structure created by tillage practices and compost application on transport processes. A modeling study was performed to evaluate how the presence of heterogeneity due to soil tillage and compost application affects water flow and pesticide dynamics in soil during a long-term period. The study was done on a plot receiving a co-compost of green wastes and sewage sludge (SGW) applied once every 2 years since 1998. The plot was cultivated with a biannual rotation of winter wheat–maize (except 1 year of barley) and a four-furrow moldboard plow was used for tillage. In each plot, wick lysimeter outflow and TDR probe data were collected at different depths from 2004, while tensiometer measurements were also conducted during 2007/2008. Isoproturon concentration was measured in lysimeter outflow since 2004. Detailed profile description was used to locate different soil structures in the profile, which was then implemented in the HYDRUS-2D model. Four zones were identified in the plowed layer: compacted clods with no visible macropores (Δ), non-compacted soil with visible macroporosity (Γ), interfurrows created by moldboard plowing containing crop residues and applied compost (IF), and the plow pan (PP) created by plowing repeatedly to the same depth. Isoproturon retention and degradation parameters were estimated from laboratory batch sorption and incubation experiments, respectively, for each structure independently. Water retention parameters were estimated from pressure plate laboratory measurements and hydraulic conductivity parameters were obtained from field tension infiltrometer experiments. Soil hydraulic properties were optimized on one calibration year (2007/08) using pressure head, water content and lysimeter outflow data, and then tested on the whole 2004/2010 period. Lysimeter outflow and water content dynamics in the soil profile were correctly described for the whole period (model efficiency coefficient: 0.99) after some correction of LAI estimates for wheat (2005/06) and barley (2006/07). Using laboratory-measured degradation rates and assuming degradation only in the liquid phase caused large overestimation of simulated isoproturon losses in lysimeter outflow. A proper order of magnitude of isoproturon losses was obtained after considering that degradation occurred in solid (sorbed) phase at a rate 75% of that in liquid phase. Isoproturon concentrations were found to be highly sensitive to degradation rates. Neither the laboratory-measured isoproturon fate parameters nor the independently-derived soil hydraulic parameters could describe the actual multiannual field dynamics of water and isoproturon without calibration. However, once calibrated on a limited period of time (9 months), HYDRUS-2D was able to simulate the whole 6-year time series with good accuracy.
    Keywords: Soil Heterogeneity ; Water Flow ; Isoproturon ; Numerical Modeling ; Hydrus-2d ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Science of the Total Environment, 15 November 2014, Vol.499, pp.560-573
    Description: Recycling composted organic residues in agriculture can reduce the need of mineral fertilizers and improve the physicochemical and biological properties of cultivated soils. However, some trace elements may accumulate in soils following repeated applications and impact other compartments of the agrosystems. This study aims at evaluating the long-term impact of such practices on the composition of soil leaching water, especially on trace metal concentrations. The field experiment QualiAgro started in 1998 on typical loess Luvisol of the Paris Basin, with a maize–wheat crop succession and five modalities: spreading of three different urban waste composts, farmyard manure (FYM), and no organic amendment (CTR). Inputs of trace metals have been close to regulatory limits, but supplies of organic matter and nitrogen overpassed common practices. Soil solutions were collected from wick lysimeters at 45 and 100 cm in one plot for each modality, during two drainage periods after the last spreading. Despite wide temporal variations, a significant effect of treatments on major solutes appears at 45 cm: DOC, Ca, K, Mg, Na, nitrate, sulphate and chloride concentrations were higher in most amended plots compared to CTR. Cu concentrations were also significantly higher in leachates of amended plots compared to CTR, whereas no clear effect emerged for Zn. The influence of amendments on solute concentrations appeared weaker at 1 m than at 45 cm, but still significant and positive for major anions and DOC. Average concentrations of Cu and Zn at 1 m depth lied in the ranges [2.5; 3.8] and [2.5; 10.5 μg/L], respectively, with values slightly higher for plots amended with sewage sludge compost or FYM than for CTR. However, leaching of both metals was less than 1% of their respective inputs through organic amendments. For Cd, most values were 〈 0.05 μg/L. So, metals added through spreading of compost or manure during 14 years may have increased metal concentrations in leachates of amended plots, in spite of increased soil organic matter, factor of metal retention. Indeed, DOC, also increased by amendments, favours the mobility of Cu; whereas pH variations, depending on treatments, influence negatively the solubility of Zn. Generic adsorption functions of these variables partly explain the variations of trace metal concentrations and helped to unravel the numerous processes induced by regular amendments with organic waste products.
    Keywords: Heavy Metal ; Trace Element ; Organic Waste ; Organic Amendment ; Cultivated Soil ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: The Science of the Total Environment, Nov 15, 2014, Vol.499, p.546(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.06.010 Byline: Vilim FilipoviA, Yves Coquet, Valerie Pot, Sabine Houot, Pierre Benoit Abstract: Transport processes in soils are strongly affected by heterogeneity of soil hydraulic properties. Tillage practices and compost amendments can modify soil structure and create heterogeneity at the local scale within agricultural fields. The long-term field experiment QualiAgro (INRA-Veolia partnership 1998-2013) explores the impact of heterogeneity in soil structure created by tillage practices and compost application on transport processes. A modeling study was performed to evaluate how the presence of heterogeneity due to soil tillage and compost application affects water flow and pesticide dynamics in soil during a long-term period. The study was done on a plot receiving a co-compost of green wastes and sewage sludge (SGW) applied once every 2years since 1998. The plot was cultivated with a biannual rotation of winter wheat-maize (except 1year of barley) and a four-furrow moldboard plow was used for tillage. In each plot, wick lysimeter outflow and TDR probe data were collected at different depths from 2004, while tensiometer measurements were also conducted during 2007/2008. Isoproturon concentration was measured in lysimeter outflow since 2004. Detailed profile description was used to locate different soil structures in the profile, which was then implemented in the HYDRUS-2D model. Four zones were identified in the plowed layer: compacted clods with no visible macropores ([DELTA]), non-compacted soil with visible macroporosity (I), interfurrows created by moldboard plowing containing crop residues and applied compost (IF), and the plow pan (PP) created by plowing repeatedly to the same depth. Isoproturon retention and degradation parameters were estimated from laboratory batch sorption and incubation experiments, respectively, for each structure independently. Water retention parameters were estimated from pressure plate laboratory measurements and hydraulic conductivity parameters were obtained from field tension infiltrometer experiments. Soil hydraulic properties were optimized on one calibration year (2007/08) using pressure head, water content and lysimeter outflow data, and then tested on the whole 2004/2010 period. Lysimeter outflow and water content dynamics in the soil profile were correctly described for the whole period (model efficiency coefficient: 0.99) after some correction of LAI estimates for wheat (2005/06) and barley (2006/07). Using laboratory-measured degradation rates and assuming degradation only in the liquid phase caused large overestimation of simulated isoproturon losses in lysimeter outflow. A proper order of magnitude of isoproturon losses was obtained after considering that degradation occurred in solid (sorbed) phase at a rate 75% of that in liquid phase. Isoproturon concentrations were found to be highly sensitive to degradation rates. Neither the laboratory-measured isoproturon fate parameters nor the independently-derived soil hydraulic parameters could describe the actual multiannual field dynamics of water and isoproturon without calibration. However, once calibrated on a limited period of time (9months), HYDRUS-2D was able to simulate the whole 6-year time series with good accuracy. Article History: Received 27 February 2014; Revised 2 June 2014; Accepted 2 June 2014
    Keywords: Hydrogeology -- Models ; Hydraulic Flow -- Models ; Waste Management -- Models ; Soil Structure -- Models ; Agricultural Land -- Models
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: The Science of the Total Environment, Nov 15, 2014, Vol.499, p.560(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.06.105 Byline: Philippe Cambier, Valerie Pot, Vincent Mercier, Aurelia Michaud, Pierre Benoit, Agathe Revallier, Sabine Houot Abstract: Recycling composted organic residues in agriculture can reduce the need of mineral fertilizers and improve the physicochemical and biological properties of cultivated soils. However, some trace elements may accumulate in soils following repeated applications and impact other compartments of the agrosystems. This study aims at evaluating the long-term impact of such practices on the composition of soil leaching water, especially on trace metal concentrations. The field experiment QualiAgro started in 1998 on typical loess Luvisol of the Paris Basin, with a maize-wheat crop succession and five modalities: spreading of three different urban waste composts, farmyard manure (FYM), and no organic amendment (CTR). Inputs of trace metals have been close to regulatory limits, but supplies of organic matter and nitrogen overpassed common practices. Soil solutions were collected from wick lysimeters at 45 and 100cm in one plot for each modality, during two drainage periods after the last spreading. Despite wide temporal variations, a significant effect of treatments on major solutes appears at 45cm: DOC, Ca, K, Mg, Na, nitrate, sulphate and chloride concentrations were higher in most amended plots compared to CTR. Cu concentrations were also significantly higher in leachates of amended plots compared to CTR, whereas no clear effect emerged for Zn. The influence of amendments on solute concentrations appeared weaker at 1m than at 45cm, but still significant and positive for major anions and DOC. Average concentrations of Cu and Zn at 1m depth lied in the ranges [2.5; 3.8] and [2.5; 10.5[mu]g/L], respectively, with values slightly higher for plots amended with sewage sludge compost or FYM than for CTR. However, leaching of both metals was less than 1% of their respective inputs through organic amendments. For Cd, most values were 〈0.05[mu]g/L. So, metals added through spreading of compost or manure during 14years may have increased metal concentrations in leachates of amended plots, in spite of increased soil organic matter, factor of metal retention. Indeed, DOC, also increased by amendments, favours the mobility of Cu; whereas pH variations, depending on treatments, influence negatively the solubility of Zn. Generic adsorption functions of these variables partly explain the variations of trace metal concentrations and helped to unravel the numerous processes induced by regular amendments with organic waste products. Article History: Received 16 March 2014; Revised 20 June 2014; Accepted 23 June 2014
    Keywords: Fertilizers ; Recycling ; Soils ; Agriculture ; Soil Leaching
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Transport in Porous Media, Nov, 2014, Vol.105(2), p.391(20)
    Description: Byline: Alain Genty (1), Valerie Pot (2) Keywords: Lattice Boltzmann method; Effective diffusion; TRT; Unsaturated; Porous media Abstract: Numerical models that solve transport of pollutants at the macroscopic scale in unsaturated porous media need the effective diffusion dependence on saturation as an input. We conducted numerical computations at the pore scale in order to obtain the effective diffusion curve as a function of saturation for an academic sphere packing porous medium and for a real porous medium where pore structure knowledge was obtained through X-ray tomography. The computations were performed using a combination of lattice Boltzmann models based on two relaxation time (TRT) scheme. The first stage of the calculations consisted in recovering the water spatial distribution into the pore structure for several fixed saturations using a phase separation TRT lattice Boltzmann model. Then, we performed diffusion computation of a non-reactive solute in the connected water structure using a diffusion TRT lattice Boltzmann model. Finally, the effective diffusion for each selected saturation value was estimated through inversion of a macroscopic classical analytical solution. Author Affiliation: (1) DEN DANS DM2S STMF, CEA-Saclay, Commissariat a l'Energie Atomique et aux Energies Alternatives, 91191, Gif sur Yvette Cedex, France (2) UMR 1091 EGC, AgroParisTech, INRA, 78850, Thiverval-Grignon, France Article History: Registration Date: 04/08/2014 Received Date: 20/03/2014 Accepted Date: 04/08/2014 Online Date: 15/08/2014
    ISSN: 0169-3913
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Soil Biology and Biochemistry, November 2014, Vol.78, pp.189-194
    Description: Modelling carbon mineralisation in natural soils is a major topic in soil and climate research. Current models need to be improved to include soil structure as an influencing factor to better predict C fluxes between pedosphere and atmosphere and to estimate carbon sequestration potentials. Geometry-based mechanistic modelling approaches have recently been developed to systematically study the effect of soil structure on carbon decomposition. Such models require spatially explicit input parameters describing the architecture of the pore space and the heterogeneous distribution of microbes and organic matter as decomposable substrate. The latter is very difficult to determine , resulting in increased uncertainty in the models. To obtain more realistic input data, we have developed a novel approach to locate soil organic matter (SOM) in undisturbed aggregates of soil using a combination of synchrotron-based X-ray microtomography and osmium as a staining agent for SOM. Here, we present the first results using 5 mm sized soil aggregate samples with contrasting C-contents in which we obtained maps of organic matter distributions in relation to the pore networks at the aggregate scale.
    Keywords: Soil Organic Matter ; Soil Structure ; Carbon Sequestration ; Synchrotron Microtomography ; Staining ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 8
    Language: French
    In: Revue Forestière Française, 2014, Issue 4, p.Fr.], ISSN 0035
    Keywords: Forestry;
    ISSN: 0035-2829
    E-ISSN: 1951-6827
    Source: CrossRef
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  • 9
    Language: English
    In: 한국토양비료학회 학술발표회 초록집, 2014, Vol.2014(6), pp.435-435
    Keywords: X-Ray Tomography ; Synchrotron ; Soil Organic Matter ; Image Analysis
    Source: DBpia - 디비피아 (Nurimedia)
    Source: DBpia (Nurimedia)
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  • 10
    Language: English
    In: Revue Forestière Française, 2014
    Keywords: Life Sciences ; Forestry
    ISSN: 0035-2829
    E-ISSN: 1951-6827
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