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  • 1
    Online Resource
    Online Resource
    Drying and rewetting cycles increased soil carbon dioxide rather than nitrous oxide emissions: A meta-analysis
    Elsevier BV ; 2022
    In:  Journal of Environmental Management Vol. 324 ( 2022-12), p. 116391-
    Details
    In: Journal of Environmental Management, Elsevier BV, Vol. 324 ( 2022-12), p. 116391-
    Type of Medium: Online Resource
    ISSN: 0301-4797
    URL: Article
    DOI: 10.1016/j.jenvman.2022.116391
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 1469206-5
    SSG: 12
    SSG: 14
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  • 2
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    Characterization of Thermal, Hydraulic, and Gas Diffusion Properties in Variably Saturated Sand Grades
    Wiley ; 2016
    In:  Vadose Zone Journal Vol. 15, No. 4 ( 2016-04), p. 1-11
    Details
    In: Vadose Zone Journal, Wiley, Vol. 15, No. 4 ( 2016-04), p. 1-11
    Abstract: This study provides physical, hydraulic, and thermal properties of five sand grades. An extended three‐region thermal conductivity model is proposed. A gas diffusivity‐based variable tortuosity parameter is examined. Useful parametric functions and descriptive models were tested. Detailed characterization of partially saturated porous media is important for understanding and predicting vadose zone transport processes. While basic properties (e.g., particle‐ and pore‐size distributions and soil‐water retention) are, in general, essential prerequisites for characterizing most porous media transport properties, key transport parameters such as thermal conductivity and gas diffusivity are particularly important to describe temperature‐induced heat transport and diffusion‐controlled gas transport processes, respectively. Despite many experimental and numerical studies focusing on a specific porous media characteristic, a single study presenting a wide range of important characteristics, together with the best‐performing functional relationships, can seldom be found. This study characterized five differently textured sand grades (Accusand no. 12/20, 20/30, 30/40, 40/50, and 50/70) in relation to physical properties, water retention, hydraulic conductivity, thermal conductivity, and gas diffusivity. We used measured basic properties and transport data to accurately parameterize the characteristic functions (particle‐ and pore‐size distributions and water retention) and descriptive transport models (thermal conductivity, saturated hydraulic conductivity, and gas diffusivity). An existing thermal conductivity model was improved to describe the distinct three‐region behavior in observed thermal conductivity–water saturation relations. Applying widely used parametric models for saturated hydraulic conductivity and soil‐gas diffusivity, we characterized porous media tortuosity in relation to grain size. Strong relations among average particle diameter, characteristic pore diameter from soil‐water retention measurements, and saturated hydraulic conductivity were found. Thus, the results of this work are useful toward better describing, linking, and predicting mass transfer and pore network properties in variably saturated porous media.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Article
    DOI: 10.2136/vzj2015.07.0097
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 2088189-7
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  • 3
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    Characterization of Grain‐Size Distribution, Thermal Conductivity, and Gas Diffusivity in Variably Saturated Binary Sand Mixtures
    Wiley ; 2018
    In:  Vadose Zone Journal Vol. 17, No. 1 ( 2018-01), p. 1-13
    Details
    In: Vadose Zone Journal, Wiley, Vol. 17, No. 1 ( 2018-01), p. 1-13
    Abstract: Parameterized models are relevant to applications where different porous media mixtures are used. Models include a grain‐size distribution function to describe bimodal behavior for binary mixtures. Improved model describes observed thermal conductivity–saturation relations for binary mixtures. Combined Buckingham–Penman model used to describe observed gas diffusivity–air content relations. This work is relevant for proper simulation of mixed porous media. Characterization of differently textured porous materials, as well as different volumetric porous media mixtures, in relation to mass and heat transport is vital for many engineering and research applications. Functional relations describing physical (e.g., grain‐size distribution, total porosity), thermal, and gas diffusion properties of porous media and mixtures are necessary to optimize the design of porous systems that involve heat and gas transport processes. However, only a limited number of studies provide characterization of soil physical, thermal, and gas diffusion properties and the functional relationships of these properties under varying soil water contents, especially for soil mixtures, complicating optimization efforts. To better understand how mixing controls the physical, thermal, and gas diffusion properties of porous media, a set of laboratory experiments was performed using five volumetric mixtures of coarse‐ and fine‐grained sand particles. For each mixture, the grain‐size distribution (GSD), thermal conductivity, and gas diffusivity were obtained and parameterized using existing and suggested parametric models. Results show that the extended, two‐region Rosin–Rammler particle‐size distribution model proposed in this study could successfully describe the bimodal behavior of the GSD of binary mixtures. Further, the modified Côté and Konrad thermal conductivity model adequately described the thermal conductivity–water saturation relations observed in different mixtures. The proposed simple soil‐gas diffusivity descriptive model parameterized the upper limit, average, and lower limit behavior in gas diffusivity–air content relations in apparently texture‐invariant gas diffusivity data. Results further show a close analogy between gas diffusivity and thermal conductivity and their variation with saturation across different binary mixtures. Overall, the results of the study provide useful numerical insight into the physical, thermal, and gas transport characteristics of binary mixtures, with wide implications for future engineering and research applications that involve multicomponent porous systems.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Article
    DOI: 10.2136/vzj2018.01.0026
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2088189-7
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  • 4
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    Density‐Corrected Models for Gas Diffusivity and Air Permeability in Unsaturated Soil
    Wiley ; 2011
    In:  Vadose Zone Journal Vol. 10, No. 1 ( 2011-02), p. 226-238
    Details
    In: Vadose Zone Journal, Wiley, Vol. 10, No. 1 ( 2011-02), p. 226-238
    Abstract: Accurate prediction of gas diffusivity ( D p / D o ) and air permeability ( k a ) and their variations with air‐filled porosity (ε) in soil is critical for simulating subsurface migration and emission of climate gases and organic vapors. Gas diffusivity and air permeability measurements from Danish soil profile data (total of 150 undisturbed soil samples) were used to investigate soil type and density effects on the gas transport parameters and for model development. The measurements were within a given range of matric potentials (−10 to −500 cm H 2 O) typically representing natural field conditions in subsurface soil. The data were regrouped into four categories based on compaction (total porosity Φ 〈 0.4 or 〉 0.4 m 3 m −3 ) and soil texture (volume‐based content of clay, silt, and organic matter 〈 15 or 〉 15%). The results suggested that soil compaction more than soil type was the major control on gas diffusivity and to some extent also on air permeability. We developed a density‐corrected (D‐C) D p (ε)/ D o model as a generalized form of a previous model for D p / D o at −100 cm H 2 O of matric potential ( D p , 100 / D o ). The D‐C model performed well across soil types and density levels compared with existing models. Also, a power‐law k a model with exponent 1.5 (derived from analogy with a previous gas diffusivity model) used in combination with the D‐C approach for k a,100 (reference point) seemed promising for k a (ε) predictions, with good accuracy and minimum parameter requirements. Finally, the new D‐C model concept for gas diffusivity was extended to bimodal (aggregated) media and performed well against data for uncompacted and compacted volcanic ash soil.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Article
    DOI: 10.2136/vzj2009.0137
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 2088189-7
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  • 5
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    Variable Pore Connectivity Model Linking Gas Diffusivity and Air‐Phase Tortuosity to Soil Matric Potential
    Wiley ; 2012
    In:  Vadose Zone Journal Vol. 11, No. 1 ( 2012-02)
    Details
    In: Vadose Zone Journal, Wiley, Vol. 11, No. 1 ( 2012-02)
    Abstract: Soil‐gas diffusivity ( D p / D o ) and its dependency on soil matric potential (ψ) is important when taking regulative measures (based on accurate predictions) for climate gas emissions and also risk‐mitigating measures (based on upper‐limit predictions) of gaseous‐phase contaminant emissions. Useful information on soil functional pore structure, e.g., pore network tortuosity and connectivity, can also be revealed from D p / D o –ψ relations. Based on D p / D o measurements in a wide range of soil types across geographically remote vadose zone profiles, this study analyzed pore connectivity for the development of a variable pore connectivity factor, X , as a function of soil matric potential, expressed as pF (=log |−ψ|), for pF values ranging from 1.0 to 3.5. The new model takes the form of X = X * ( F / F *) A with F = 1 + pF −1 , where X * is the pore network tortuosity at reference F ( F* ) and A is a model parameter that accounts for water blockage. The X –pF relation can be linked to drained pore size to explain the lower probability of the larger but far fewer air‐filled pores at lower pF effectively interconnecting and promoting gas diffusion. The model with X* = 2 and A = 0.5 proved promising for generalizing D p / D o predictions across soils of wide geographic contrast and yielded results comparable to those from widely used predictive models. The X –pF model additionally proved valuable for differentiating between soils (providing a unique soil structural fingerprint for each soil layer) and also between the inter‐ and intraaggregate pore regions of aggregated soils. We further suggest that the new model with parameter values of X * = 1.7 and A = 0 may be used for upper limit D p / D o predictions in risk assessments of, e.g., fluxes of toxic volatile organics from soil to indoor air at polluted soil sites.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Article
    DOI: 10.2136/vzj2011.0096
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2088189-7
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  • 6
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    Generalized Density‐Corrected Model for Gas Diffusivity in Variably Saturated Soils
    Wiley ; 2011
    In:  Soil Science Society of America Journal Vol. 75, No. 4 ( 2011-07), p. 1315-1329
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 75, No. 4 ( 2011-07), p. 1315-1329
    Abstract: Accurate predictions of the soil‐gas diffusivity ( D p / D o , where D p is the soil‐gas diffusion coefficient and D o is the diffusion coefficient in free air) from easily measureable parameters like air‐filled porosity (ε) and soil total porosity (ϕ) are valuable when predicting soil aeration and the emission of greenhouse gases and gaseous‐phase contaminants from soils. Soil type (texture) and soil density (compaction) are two key factors controlling gas diffusivity in soils. We extended a recently presented density‐corrected D p (ε)/ D o model by letting both model parameters (α and β) be interdependent and also functions of ϕ. The extension was based on literature measurements on Dutch and Danish soils ranging from sand to peat. The parameter α showed a promising linear relation to total porosity, while β also varied with α following a weak linear relation. The thus generalized density‐corrected (GDC) model gave improved predictions of diffusivity across a wide range of soil types and density levels when tested against two independent data sets (total of 280 undisturbed soils or soil layers) representing Danish soil profile data (0–8 m below the ground surface) and performed better than existing models. The GDC model was further extended to describe two‐region (bimodal) soils and could describe and predict D p / D o well for both different soil aggregate size fractions and variably compacted volcanic ash soils. A possible use of the new GDC model is engineering applications such as the design of highly compacted landfill site caps.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj2010.0405
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 7
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    Online Resource
    Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates
    Elsevier BV ; 2014
    In:  Advances in Space Research Vol. 54, No. 4 ( 2014-08), p. 797-808
    Details
    In: Advances in Space Research, Elsevier BV, Vol. 54, No. 4 ( 2014-08), p. 797-808
    Type of Medium: Online Resource
    ISSN: 0273-1177
    URL: Article
    DOI: 10.1016/j.asr.2014.04.018
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 2023311-5
    SSG: 16,12
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  • 8
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    Soil‐Gas Diffusivity and Soil‐Moisture effects on N 2 O Emissions from Intact Pasture Soils
    Wiley ; 2019
    In:  Soil Science Society of America Journal Vol. 83, No. 4 ( 2019-07), p. 1032-1043
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 83, No. 4 ( 2019-07), p. 1032-1043
    Abstract: Grazed pastures are recognized as a dominant source of nitrous oxide (N 2 O), a highly potent greenhouse gas. Studies have examined soil physical controls on N 2 O emissions, including soil moisture status. Limited attempts to link N 2 O emissions with soil‐diffusivity ( D p / D o ), using repacked soil cores, have shown peak N 2 O emissions to align with a relatively narrow window of D p / D o , despite a relatively wide range in water‐filled pore space (WFPS), across a range of soil bulk densities. Such detailed studies have not been performed with intact soil cores. We investigated the effects of soil‐water characteristic (SWC) and D p / D o on N 2 O emissions from intact soil samples, retrieved at three depths (0–5, 5–10, 10–15 cm) from three perennial pasture sites that received a KNO 3 solution (1800 mg, N mL −1 ). We observed distinct fingerprints of SWC and D p / D o , which showed clear effects of soil structure on diffusion‐controlled gas emissions. Depth‐wise variation in soil moisture diminished as the soil was subjected to higher matric potential ( 〉 ∼ ‐100 kPa). Variation in D p / D o , was more pronounced in the dry soil ( 〉 ∼ ‐1000 kPa), being largely constrained by soil moisture in wet soil (∼ ‐100 kPa) with little depth‐wise variation. Measured N 2 O fluxes peaked within narrow ranges of WFPS and D p / D o , 0.90–0.95 and 0.005–0.01, respectively. The value of D p / D o can be determined using parametric models and presents a pasture management (e.g., irrigation, soil physical disturbance such as pasture renovation and animal treading)) tool to minimize N 2 O emissions: soil D p / D o should be maintained above a range of 0.005–0.01 to minimize N 2 O emissions. Core Ideas Peak N 2 O fluxes from intact soil cores occurred when diffusivity ranged from 0.005–0.01 This peak N 2 O flux diffusivity range was 0.005–0.01 regardless of soil or depth (0–15 cm) The diffusivity range for peak N 2 O flux equalled that observed in repacked soil cores Diffusivity values are readily determined and add to the suite of soil management tools
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj2018.10.0405
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 9
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    Online Resource
    Structure‐Dependent Water‐Induced Linear Reduction Model for Predicting Gas Diffusivity and Tortuosity in Repacked and Intact Soil
    Wiley ; 2013
    In:  Vadose Zone Journal Vol. 12, No. 3 ( 2013-08), p. 1-11
    Details
    In: Vadose Zone Journal, Wiley, Vol. 12, No. 3 ( 2013-08), p. 1-11
    Abstract: The soil‐gas diffusion is a primary driver of transport, reactions, emissions, and uptake of vadose zone gases, including oxygen, greenhouse gases, fumigants, and spilled volatile organics. The soil‐gas diffusion coefficient, D p , depends not only on soil moisture content, texture, and compaction but also on the local‐scale variability of these. Different predictive models have been developed to estimate D p in intact and repacked soil, but clear guidelines for model choice at a given soil state are lacking. In this study, the water‐induced linear reduction (WLR) model for repacked soil is made adaptive for different soil structure conditions (repacked, intact) by introducing a media complexity factor ( C m ) in the dry media term of the model. With C m = 1, the new structure‐dependent WLR (SWLR) model accurately predicted soil‐gas diffusivity ( D p / D o , where D o is the gas diffusion coefficient in free air) in repacked soils containing between 0 and 54% clay. With C m = 2.1, the SWLR model on average gave excellent predictions for 290 intact soils, performing well across soil depths, textures, and compactions (dry bulk densities). The SWLR model generally outperformed similar, simple D p / D o models also depending solely on total and air‐filled porosity. With C m = 3, the SWLR performed well as a lower‐limit D p / D o model, which is useful in terms of predicting critical air‐filled porosity for adequate soil aeration. Because the SWLR model distinguishes between and well represents both repacked and intact soil conditions, this model is recommended for use in simulations of gas diffusion and fate in the soil vadose zone, for example, as a key element in developing more accurate climate change models.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Article
    DOI: 10.2136/vzj2013.01.0026
    Language: English
    Publisher: Wiley
    Publication Date: 2013
    detail.hit.zdb_id: 2088189-7
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  • 10
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    The Water‐Induced Linear Reduction Gas Diffusivity Model Extended to Three Pore Regions
    Wiley ; 2015
    In:  Vadose Zone Journal Vol. 14, No. 10 ( 2015-10), p. 1-9
    Details
    In: Vadose Zone Journal, Wiley, Vol. 14, No. 10 ( 2015-10), p. 1-9
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Article
    DOI: 10.2136/vzj2015.04.0051
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2088189-7
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