Luis Alfredo Pires Barbosa, Fernando Vieira Lima, Horst H. Gerke
The surface coating of biopores plays a pivotal role in mediating mass exchange between the biopore and the soil matrix, ultimately governing preferential flow in structured soils. However, quantitative experiments of the flow exchange dynamics in the soil around an earthworm burrow (drilosphere) are limited. Here, we developed an experimental setup to mimic preferential flow within a biopore while monitoring the water distribution by neutron radiography. The objective was to quantify the evolving water content distribution in the biopore with surrounding drilosphere samples from Bt and C horizons. We hypothesize that the distribution of clay and organic material across biopore surfaces in Bt and C horizons impacts the biopore coating material formation (i.e., composition and thickness), thereby influencing its role in controlling mass exchange during preferential flow events. The experimental setup was proposed for in situ quantification of the preferential flow dynamics in an earthworm burrow (biopore) passing through Bt and C horizons of a Luvisol developed on glacial till. The neutron radiographies were obtained at the NEUtron Transmission Radiography facility of the Paul Scherrer Institut, Villingen. The volumetric water content was quantified by calibrating gray scale values from radiography images with defined water contents using stepped aluminum cuvettes attached to the samples; image analysis was used to determine sorptivity at the biopore–soil matrix interface. The water exchange flow was found to be smaller for coated biopore surface in the more clayey Bt horizon, as compared to the coarser textured carbonaceous subsoil C horizon, where higher sorptivity intensified mass exchange. The method most realistically captured the dynamics of the vertical preferential flow process in a biopore, including lateral exchange flow, by determining the water sorptivity of the drilosphere. In contrast to mini‐infiltrometer data, biopore–matrix exchange flow was here more restricted for Bt in contrast to carbonaceous C horizon. Since both horizons showed the presence of coating material on their burrow walls, the results suggest further analysis of their contrasting properties and structures.
生物孔的表面涂层在介导生物孔与土壤基质之间的质量交换方面起着关键作用，最终控制着结构化土壤中的优先流动。然而，有关蚯蚓洞穴（钻孔层）周围土壤中流动交换动态的定量实验非常有限。在此，我们开发了一种实验装置，用于模拟生物孔内的优先流动，同时通过中子射线照相术监测水的分布。目的是量化生物孔内不断变化的含水量分布以及周围来自 Bt 和 C 层的钻孔层样本。我们假设，Bt 和 C 地层生物孔表面粘土和有机物的分布会影响生物孔涂层材料的形成（即成分和厚度），从而影响其在优先流动事件中控制质量交换的作用。该实验装置用于现场量化穿过冰碛物上发育的卢维索尔 Bt 和 C 地层的蚯蚓洞穴（生物孔）中的优先流动态。中子射线照片是在维林根保罗-舍勒研究所的 NEUtron 透射射线照相设备上获得的。通过使用附着在样品上的阶梯状铝制比色皿，将射线成像图像中的灰度值与定义的含水量进行校准，从而对体积含水量进行量化；图像分析用于确定生物孔隙-土壤基质界面的吸水率。结果发现，在粘质较多的 Bt 地层中，涂覆生物孔表面的水交换流量较小，而在质地较粗的碳质底土 C 地层中，较高的吸水率会加强质量交换。该方法通过测定钻孔层的吸水率，最真实地捕捉到了生物孔中垂直优先流动过程的动态，包括横向交换流。与微型浸润器数据相比，生物孔-基质交换流在 Bt 层比碳质 C 层受到更多限制。由于这两种地层的钻孔壁上都有涂层材料，因此研究结果建议进一步分析它们的不同性质和结构。
{"title":"Neutron imaging of exchange flow between biopore and matrix for Bt versus C horizons","authors":"Luis Alfredo Pires Barbosa, Fernando Vieira Lima, Horst H. Gerke","doi":"10.1002/vzj2.20320","DOIUrl":"https://doi.org/10.1002/vzj2.20320","url":null,"abstract":"The surface coating of biopores plays a pivotal role in mediating mass exchange between the biopore and the soil matrix, ultimately governing preferential flow in structured soils. However, quantitative experiments of the flow exchange dynamics in the soil around an earthworm burrow (drilosphere) are limited. Here, we developed an experimental setup to mimic preferential flow within a biopore while monitoring the water distribution by neutron radiography. The objective was to quantify the evolving water content distribution in the biopore with surrounding drilosphere samples from Bt and C horizons. We hypothesize that the distribution of clay and organic material across biopore surfaces in Bt and C horizons impacts the biopore coating material formation (i.e., composition and thickness), thereby influencing its role in controlling mass exchange during preferential flow events. The experimental setup was proposed for in situ quantification of the preferential flow dynamics in an earthworm burrow (biopore) passing through Bt and C horizons of a Luvisol developed on glacial till. The neutron radiographies were obtained at the NEUtron Transmission Radiography facility of the Paul Scherrer Institut, Villingen. The volumetric water content was quantified by calibrating gray scale values from radiography images with defined water contents using stepped aluminum cuvettes attached to the samples; image analysis was used to determine sorptivity at the biopore–soil matrix interface. The water exchange flow was found to be smaller for coated biopore surface in the more clayey Bt horizon, as compared to the coarser textured carbonaceous subsoil C horizon, where higher sorptivity intensified mass exchange. The method most realistically captured the dynamics of the vertical preferential flow process in a biopore, including lateral exchange flow, by determining the water sorptivity of the drilosphere. In contrast to mini‐infiltrometer data, biopore–matrix exchange flow was here more restricted for Bt in contrast to carbonaceous C horizon. Since both horizons showed the presence of coating material on their burrow walls, the results suggest further analysis of their contrasting properties and structures.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"250 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140200930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tiago B. Ramos, Maria C. Gonçalves, Martinus Th. van Genuchten
Soil salinization poses a significant threat to agricultural production in Portugal. Collaborative research spanning three decades with the U.S. Salinity Laboratory in Riverside, California, has been instrumental in advancing our understanding of this issue. This study provides a concise overview of the causes of soil salinization in Portugal, focusing on ongoing efforts to comprehensively address this challenge. Key advancements highlighted in this study encompass the meticulous characterization of soil hydraulic and solute transport parameters, the application of cutting‐edge modeling tools for water flow and solute transport in diverse agricultural systems, and the utilization of innovative proximal and remote sensing methods for mapping soil salinity. Noteworthy results and practical implications of these advancements underscore their relevance in real‐world scenarios. While celebrating these achievements, the study emphasizes the current nature of the ongoing research, highlighting the dynamic landscape of soil salinization. The study underscores the imperative need for further advancements to effectively cope with soil salinization, especially in anticipation of the intensification of agricultural practices and the looming impacts of climate change. This comprehensive overview not only encapsulates past achievements but also sets the stage for future research endeavors in mitigating the pervasive effects of soil salinization on agricultural sustainability in Portugal.
{"title":"Soil salinization in Portugal: An in‐depth exploration of impact, advancements, and future considerations","authors":"Tiago B. Ramos, Maria C. Gonçalves, Martinus Th. van Genuchten","doi":"10.1002/vzj2.20314","DOIUrl":"https://doi.org/10.1002/vzj2.20314","url":null,"abstract":"Soil salinization poses a significant threat to agricultural production in Portugal. Collaborative research spanning three decades with the U.S. Salinity Laboratory in Riverside, California, has been instrumental in advancing our understanding of this issue. This study provides a concise overview of the causes of soil salinization in Portugal, focusing on ongoing efforts to comprehensively address this challenge. Key advancements highlighted in this study encompass the meticulous characterization of soil hydraulic and solute transport parameters, the application of cutting‐edge modeling tools for water flow and solute transport in diverse agricultural systems, and the utilization of innovative proximal and remote sensing methods for mapping soil salinity. Noteworthy results and practical implications of these advancements underscore their relevance in real‐world scenarios. While celebrating these achievements, the study emphasizes the current nature of the ongoing research, highlighting the dynamic landscape of soil salinization. The study underscores the imperative need for further advancements to effectively cope with soil salinization, especially in anticipation of the intensification of agricultural practices and the looming impacts of climate change. This comprehensive overview not only encapsulates past achievements but also sets the stage for future research endeavors in mitigating the pervasive effects of soil salinization on agricultural sustainability in Portugal.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"23 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140165376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuankai Yang, Ravi A. Patel, Nikolaos I. Prasianakis, Sergey V. Churakov, Guido Deissmann, Dirk Bosbach
Solute diffusion in partially saturated porous media is an important fundamental process in many natural and environmental systems. At low water saturation, the solute transport is governed by the diffusion in thin water films on the surfaces of solids. In this study, we established an improved pore-scale simulation framework successfully describing the solute diffusion in variably saturated porous media (e.g., soils), which considers the contribution of the diffusion within the thin water film on the surface of the solid matrix. The model takes into account the liquid–gas distribution in the underlying porous media by the Shan-Chen lattice Boltzmann Method (LBM) and simulates the solute diffusion in the bulk liquid phase and the water film. Based on the numerical results, an easy-to-use theoretical formula was also developed to predict the effective diffusivity in microporous materials at low saturation levels. The average relative error of its prediction with respect to the experimental data from the literature is about 30%, while that of the classical power law exceeds 70%. A simple phase diagram was defined, which allows us to identify the situations under which it is necessary to take the influence of surface water films on the effective diffusivity in unsaturated microporous media into account. The present study improves the pore-scale model to address solute diffusion in the water films at low water saturation and elucidates the contribution of thin water films on solute transport.
{"title":"Elucidating the role of water films on solute diffusion in unsaturated porous media by improved pore-scale modeling","authors":"Yuankai Yang, Ravi A. Patel, Nikolaos I. Prasianakis, Sergey V. Churakov, Guido Deissmann, Dirk Bosbach","doi":"10.1002/vzj2.20321","DOIUrl":"https://doi.org/10.1002/vzj2.20321","url":null,"abstract":"Solute diffusion in partially saturated porous media is an important fundamental process in many natural and environmental systems. At low water saturation, the solute transport is governed by the diffusion in thin water films on the surfaces of solids. In this study, we established an improved pore-scale simulation framework successfully describing the solute diffusion in variably saturated porous media (e.g., soils), which considers the contribution of the diffusion within the thin water film on the surface of the solid matrix. The model takes into account the liquid–gas distribution in the underlying porous media by the Shan-Chen lattice Boltzmann Method (LBM) and simulates the solute diffusion in the bulk liquid phase and the water film. Based on the numerical results, an easy-to-use theoretical formula was also developed to predict the effective diffusivity in microporous materials at low saturation levels. The average relative error of its prediction with respect to the experimental data from the literature is about 30%, while that of the classical power law exceeds 70%. A simple phase diagram was defined, which allows us to identify the situations under which it is necessary to take the influence of surface water films on the effective diffusivity in unsaturated microporous media into account. The present study improves the pore-scale model to address solute diffusion in the water films at low water saturation and elucidates the contribution of thin water films on solute transport.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"155 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140155342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Albara Almawazreh, Daniel Uteau, C. T. Subbarayappa, Andreas Buerkert, Sybille Lehmann, Stephan Peth
The understanding of the impact of nitrogen (N) fertilization on the field water cycle and corresponding water use efficiency (WUE) is very important for optimizing fertilization rates and conserving stressed water resources. We modeled soil moisture dynamics of maize (Zea mays L.), finger millet (Eleusine coracana Gaertn.), and lablab [Lablab purpureus (L..) Sweet] plots using calibrated HYDRUS‐1D model on two experimental sites (rain‐fed and irrigated) for three seasons under different N treatments. The results indicate that the effects of N depended on plant specific properties such as N‐fixation and drought tolerance, and on plant available water content governed by soil structure and rainfall seasonal variability. Maize WUE of plots which received 150 kg/ha of urea (46 N) were 10–30 kg/ha/mm higher than plots which received none; likewise, millet that received 50 kg/ha of urea had a 7–10 kg/ha/mm higher WUE than control plots in both experiments. However, differences in water cycle components were noticeable between N treatments only in the rain‐fed experiment, where higher N levels led to around 60 and 30 mm higher transpiration, 30 and 20 mm lower evaporation, and 30 and 15 mm lower percolation per season for maize and millet, respectively. In 2018, which was the driest year, the difference in maize WUE between the high and low N treatments was only 1 kg/ha/mm, which corresponded with low actual to potential transpiration ratios (). This indicates higher sensitivity of maize to water stress compared to the other crops. The results of lablab indicate a positive impact of N fertilization on WUE only under water‐limited conditions.
{"title":"Modeling N fertilization impact on water cycle and water use efficiency of maize, finger‐millet, and lablab crops in South India","authors":"Albara Almawazreh, Daniel Uteau, C. T. Subbarayappa, Andreas Buerkert, Sybille Lehmann, Stephan Peth","doi":"10.1002/vzj2.20319","DOIUrl":"https://doi.org/10.1002/vzj2.20319","url":null,"abstract":"The understanding of the impact of nitrogen (N) fertilization on the field water cycle and corresponding water use efficiency (WUE) is very important for optimizing fertilization rates and conserving stressed water resources. We modeled soil moisture dynamics of maize (<jats:italic>Zea mays</jats:italic> L.), finger millet (<jats:italic>Eleusine coracana Gaertn</jats:italic>.), and lablab [<jats:italic>Lablab purpureus</jats:italic> (L..) <jats:italic>Sweet</jats:italic>] plots using calibrated HYDRUS‐1D model on two experimental sites (rain‐fed and irrigated) for three seasons under different N treatments. The results indicate that the effects of N depended on plant specific properties such as N‐fixation and drought tolerance, and on plant available water content governed by soil structure and rainfall seasonal variability. Maize WUE of plots which received 150 kg/ha of urea (46 N) were 10–30 kg/ha/mm higher than plots which received none; likewise, millet that received 50 kg/ha of urea had a 7–10 kg/ha/mm higher WUE than control plots in both experiments. However, differences in water cycle components were noticeable between N treatments only in the rain‐fed experiment, where higher N levels led to around 60 and 30 mm higher transpiration, 30 and 20 mm lower evaporation, and 30 and 15 mm lower percolation per season for maize and millet, respectively. In 2018, which was the driest year, the difference in maize WUE between the high and low N treatments was only 1 kg/ha/mm, which corresponded with low actual to potential transpiration ratios (). This indicates higher sensitivity of maize to water stress compared to the other crops. The results of lablab indicate a positive impact of N fertilization on WUE only under water‐limited conditions.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"31 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140154899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Over the last 30 years, the impact of climate change in Berlin, Germany, has manifested in the form of reduced summer rainfall, elevated temperatures, and a notable rise in the frequency of days with temperatures surpassing 30°C. All of them are leading to a decreasing water supply and increasing risk of drought. Various field, laboratory, and numerical simulation studies have been done for deriving information on long‐term potential and actual evapotranspiration, water stress during the vegetation period (April–September), and tree ring growth of various pine tree stands in Berlin. Data analysis highlights periodical climate patterns and complex interactions between drought, water supply, and plant growth. Annual tree ring growth is not only related to the actual weather conditions but also to the past climate years. With decreasing water supply, this kind of drought memory effect increases up to 5 years into the past. For Berlin's climate, it is noteworthy that late summer, particularly the water stress in August, represents the most sensitive indicator for tree ring growth.For regionalization purposes, long‐term numerical simulations were done to derive hydro‐pedo‐transfer‐functions (HPTFs) predicting the water stress coefficient of the growing season (Eact‐s/Epot‐s). They only need easily available information such as soil texture, climate water balance, and groundwater depth. Two HPTFs were successfully tested and can be easily applied by geo‐information systems. However, for other climate regions and tree species, HPTFs need to be adapted.
{"title":"Hydro‐pedo‐transfer‐functions expressing drought and memory effects on pine tree growth","authors":"Gerd Wessolek, Winfried Riek, Klaus Bohne","doi":"10.1002/vzj2.20317","DOIUrl":"https://doi.org/10.1002/vzj2.20317","url":null,"abstract":"Over the last 30 years, the impact of climate change in Berlin, Germany, has manifested in the form of reduced summer rainfall, elevated temperatures, and a notable rise in the frequency of days with temperatures surpassing 30°C. All of them are leading to a decreasing water supply and increasing risk of drought. Various field, laboratory, and numerical simulation studies have been done for deriving information on long‐term potential and actual evapotranspiration, water stress during the vegetation period (April–September), and tree ring growth of various pine tree stands in Berlin. Data analysis highlights periodical climate patterns and complex interactions between drought, water supply, and plant growth. Annual tree ring growth is not only related to the actual weather conditions but also to the past climate years. With decreasing water supply, this kind of drought memory effect increases up to 5 years into the past. For Berlin's climate, it is noteworthy that late summer, particularly the water stress in August, represents the most sensitive indicator for tree ring growth.For regionalization purposes, long‐term numerical simulations were done to derive hydro‐pedo‐transfer‐functions (HPTFs) predicting the water stress coefficient of the growing season (<jats:italic>E</jats:italic><jats:sub>act‐s</jats:sub>/<jats:italic>E</jats:italic><jats:sub>pot‐s</jats:sub>). They only need easily available information such as soil texture, climate water balance, and groundwater depth. Two HPTFs were successfully tested and can be easily applied by geo‐information systems. However, for other climate regions and tree species, HPTFs need to be adapted.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"15 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140019678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Few contaminants have been linked to more devastating human health and environmental impacts than carcinogenic arsenic (As). Geogenic As contamination of groundwater used as a drinking water source continues to threaten hundreds of millions of lives worldwide, with the As crisis in South and Southeast Asia often called “the largest mass poisoning in history.” In addition, anthropogenic As pollution derived from industrial activities (e.g., mining and smelting processes, wood preservation, and historic pesticide use) has created large sites of intensely contaminated soils and water bodies that urgently require remediation. Because of its profound negative impacts on environmental quality, As has also been the focus of considerable scientific research. In particular, vadose zone research, which aims to understand fluid flow and contaminant transport in variably saturated porous media, has been critical to identify sources of As contamination, predict the fate of As in natural and engineered systems, and help guide regulatory agencies, policymakers, and practitioners to minimize As impacts. In this work, we review several key topics in global As research that have been advanced by vadose zone knowledge. These topics include the release of geogenic As to groundwater, the remediation of anthropogenic As contamination, and the design and operation of As treatment systems. We end this review by highlighting urgent and important knowledge gaps in As research that can benefit from a more rigorous understanding of vadose zone processes.
{"title":"Vadose zone perspectives in global arsenic research: A review and future opportunities","authors":"C. M. van Genuchten, K. Wang, R. Jakobsen","doi":"10.1002/vzj2.20313","DOIUrl":"https://doi.org/10.1002/vzj2.20313","url":null,"abstract":"Few contaminants have been linked to more devastating human health and environmental impacts than carcinogenic arsenic (As). Geogenic As contamination of groundwater used as a drinking water source continues to threaten hundreds of millions of lives worldwide, with the As crisis in South and Southeast Asia often called “the largest mass poisoning in history.” In addition, anthropogenic As pollution derived from industrial activities (e.g., mining and smelting processes, wood preservation, and historic pesticide use) has created large sites of intensely contaminated soils and water bodies that urgently require remediation. Because of its profound negative impacts on environmental quality, As has also been the focus of considerable scientific research. In particular, vadose zone research, which aims to understand fluid flow and contaminant transport in variably saturated porous media, has been critical to identify sources of As contamination, predict the fate of As in natural and engineered systems, and help guide regulatory agencies, policymakers, and practitioners to minimize As impacts. In this work, we review several key topics in global As research that have been advanced by vadose zone knowledge. These topics include the release of geogenic As to groundwater, the remediation of anthropogenic As contamination, and the design and operation of As treatment systems. We end this review by highlighting urgent and important knowledge gaps in As research that can benefit from a more rigorous understanding of vadose zone processes.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"30 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140004516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Direct information about the soil structure can be obtained with X‐ray computed microtomography, and the imaged macropore networks can be used as geometries in the lattice Boltzmann flow simulations. This method has not been widely applied for near‐saturated flows due to methodological issues related to diffuse‐interface two‐phase flow simulations in samples with limited resolution. Here, a simple pore‐scale lattice Boltzmann approach to simulate steady‐state water flow in partially saturated soil macropore networks that circumvents these problems is presented. The actual simulation is preceded by the determination of water–air distribution, for example, by using morphological operations. Flow through the water‐filled part of the pore space is done by using no‐slip conditions at water–solid boundaries and slip conditions at water–air interfaces. The method was tested by simulating film flow over a solid surface, and the numerical results are shown to agree with the analytical expression available for this flow geometry. The method is further tested, and its use is demonstrated with real tomographic reconstructions of clay soil samples.
土壤结构的直接信息可通过 X 射线计算显微层析成像法获得，成像的大孔隙网络可用作晶格玻尔兹曼流动模拟的几何图形。由于在分辨率有限的样品中进行扩散界面两相流模拟存在方法问题，因此这种方法尚未广泛应用于近饱和流动。本文介绍了一种简单的孔隙尺度晶格玻尔兹曼方法，用于模拟部分饱和土壤大孔隙网络中的稳态水流，从而规避了这些问题。在实际模拟之前，首先要确定水气分布，例如通过形态运算。通过在水-固边界使用无滑动条件和在水-气界面使用滑动条件来实现孔隙空间充满水部分的流动。通过模拟固体表面上的薄膜流动，对该方法进行了测试，结果表明数值结果与该流动几何形状的分析表达式一致。对该方法进行了进一步测试，并通过粘土样本的真实层析重建演示了该方法的应用。
{"title":"Simulation of near‐saturated flow in soil macropores with the lattice Boltzmann method","authors":"Jari Hyväluoma","doi":"10.1002/vzj2.20318","DOIUrl":"https://doi.org/10.1002/vzj2.20318","url":null,"abstract":"Direct information about the soil structure can be obtained with X‐ray computed microtomography, and the imaged macropore networks can be used as geometries in the lattice Boltzmann flow simulations. This method has not been widely applied for near‐saturated flows due to methodological issues related to diffuse‐interface two‐phase flow simulations in samples with limited resolution. Here, a simple pore‐scale lattice Boltzmann approach to simulate steady‐state water flow in partially saturated soil macropore networks that circumvents these problems is presented. The actual simulation is preceded by the determination of water–air distribution, for example, by using morphological operations. Flow through the water‐filled part of the pore space is done by using no‐slip conditions at water–solid boundaries and slip conditions at water–air interfaces. The method was tested by simulating film flow over a solid surface, and the numerical results are shown to agree with the analytical expression available for this flow geometry. The method is further tested, and its use is demonstrated with real tomographic reconstructions of clay soil samples.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"1 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140004419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Swamini Khurana, Falk Heße, Anke Hildebrandt, Martin Thullner
Spatially distributed properties of the subsurface result in varying water saturation and preferential flow paths, which lead to heterogeneous solute transport patterns and heterogeneous microbial environments. This, in turn, influences the distribution of nutrients and energy gradients, microbial biomass, and activity thereof. By their very nature, current field sampling techniques do not resolve subsampling scale heterogeneities in microbial biomass and activity, resulting in inaccurate estimates of microbially mediated carbon and nitrogen turnover in the heterogeneous subsurface. Thus, in this study, we undertook a numerical modeling approach to study the impact of spatial heterogeneity on microbially mediated carbon and nitrogen turnover in the vadose zone. We adapted an established biogeochemical process network that captures a variety of respiration pathways, carbon decomposition strategies, and microbial life processes to simulate microbially mediated carbon and nitrogen turnover in variably saturated spatially heterogeneous settings, using an established numerical tool (OGS#BRNS). The fractionation of microbial communities into active and inactive states, as well as immobile and mobile states followed could be linked to the bulk average saturation. Lastly, we identified three reactive systems, distinguished by the rate ratio of aerobic respiration and transfer of oxygen from the air to the water phase, to evaluate the impact of spatial heterogeneity on carbon and nitrogen removal in subsurface heterogeneous domains. Specifically, when this ratio is approximately 1, there is no impact on carbon removal, while when this ratio is very high, then carbon removal decreases as the domain tends to be oxygen limited.
{"title":"Microbial mediated carbon and nitrogen cycling in the spatially heterogeneous vadose zone: A modeling study","authors":"Swamini Khurana, Falk Heße, Anke Hildebrandt, Martin Thullner","doi":"10.1002/vzj2.20315","DOIUrl":"https://doi.org/10.1002/vzj2.20315","url":null,"abstract":"Spatially distributed properties of the subsurface result in varying water saturation and preferential flow paths, which lead to heterogeneous solute transport patterns and heterogeneous microbial environments. This, in turn, influences the distribution of nutrients and energy gradients, microbial biomass, and activity thereof. By their very nature, current field sampling techniques do not resolve subsampling scale heterogeneities in microbial biomass and activity, resulting in inaccurate estimates of microbially mediated carbon and nitrogen turnover in the heterogeneous subsurface. Thus, in this study, we undertook a numerical modeling approach to study the impact of spatial heterogeneity on microbially mediated carbon and nitrogen turnover in the vadose zone. We adapted an established biogeochemical process network that captures a variety of respiration pathways, carbon decomposition strategies, and microbial life processes to simulate microbially mediated carbon and nitrogen turnover in variably saturated spatially heterogeneous settings, using an established numerical tool (OGS#BRNS). The fractionation of microbial communities into active and inactive states, as well as immobile and mobile states followed could be linked to the bulk average saturation. Lastly, we identified three reactive systems, distinguished by the rate ratio of aerobic respiration and transfer of oxygen from the air to the water phase, to evaluate the impact of spatial heterogeneity on carbon and nitrogen removal in subsurface heterogeneous domains. Specifically, when this ratio is approximately 1, there is no impact on carbon removal, while when this ratio is very high, then carbon removal decreases as the domain tends to be oxygen limited.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"30 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140004513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yang Yang, Tingting Peng, Hui Zhang, Ole Wendroth, Zixin Jin, Xinyi Chen, Yingna Liu
Reliable estimates of saturated hydraulic conductivity (Ks) are usually difficult to obtain, as Ks is regulated by a variety of soil processes acting at different spatial scales that may obscure each other's impacts. We hypothesized that these scale-specific relationships could be well characterized with the aid of the noise-assisted multivariate empirical mode decomposition (NA-MEMD), thereby serving as a solid foundation for an accurate Ks prediction. The objective was to evaluate whether the incorporation of NA-MEMD could improve the estimation of Ks based on the multiscale associations it unraveled. On a typical slope transect of 860 m in the black soil region of northeast China, Ks, mollic epipedon thickness, bulk density, soil organic carbon content, total (ϕ) and effective porosities (ϕe), and particle size distribution were investigated at every 20 m. Prior to NA-MEMD, Ks was most strongly correlated with ϕe, and the linear regression models based on ϕe solely were satisfactory for Ks estimation at the scale of investigation. Adding other predictors significantly improved Ks prediction in calibration, but impaired it in validation. Upon decomposition by NA-MEMD, Ks was found to be significantly associated with each attribute at two scales of oscillation at least. Summing up the estimates of each Ks component derived from the properties at the equivalent oscillation scales, the results outperformed the traditional multiple linear regressions made at the investigation scale, when the same sets of predictors were used. The application of NA-MEMD, moreover, could save the tedious measurements of ϕe and ϕ. Excluding these two porosity-related properties, Ks estimates obtained by incorporating NA-MEMD were statistically similar or even better than those involving them before NA-MEMD. These findings demonstrate the great potential of NA-MEMD in untangling scale-dependent relationships of Ks with various processes and hold important implications for future estimations of Ks and other hydraulic properties in the black soil region of northeast China and similar regions.
{"title":"Disentangling slope-scale spatial variability of saturated hydraulic conductivity in the black soil region of northeast China using noise-assisted multivariate empirical mode decomposition","authors":"Yang Yang, Tingting Peng, Hui Zhang, Ole Wendroth, Zixin Jin, Xinyi Chen, Yingna Liu","doi":"10.1002/vzj2.20311","DOIUrl":"https://doi.org/10.1002/vzj2.20311","url":null,"abstract":"Reliable estimates of saturated hydraulic conductivity (<i>K</i><sub>s</sub>) are usually difficult to obtain, as <i>K</i><sub>s</sub> is regulated by a variety of soil processes acting at different spatial scales that may obscure each other's impacts. We hypothesized that these scale-specific relationships could be well characterized with the aid of the noise-assisted multivariate empirical mode decomposition (NA-MEMD), thereby serving as a solid foundation for an accurate <i>K</i><sub>s</sub> prediction. The objective was to evaluate whether the incorporation of NA-MEMD could improve the estimation of <i>K</i><sub>s</sub> based on the multiscale associations it unraveled. On a typical slope transect of 860 m in the black soil region of northeast China, <i>K</i><sub>s</sub>, mollic epipedon thickness, bulk density, soil organic carbon content, total (<i>ϕ</i>) and effective porosities (<i>ϕ</i><sub>e</sub>), and particle size distribution were investigated at every 20 m. Prior to NA-MEMD, <i>K</i><sub>s</sub> was most strongly correlated with <i>ϕ</i><sub>e</sub>, and the linear regression models based on <i>ϕ</i><sub>e</sub> solely were satisfactory for <i>K</i><sub>s</sub> estimation at the scale of investigation. Adding other predictors significantly improved <i>K</i><sub>s</sub> prediction in calibration, but impaired it in validation. Upon decomposition by NA-MEMD, <i>K</i><sub>s</sub> was found to be significantly associated with each attribute at two scales of oscillation at least. Summing up the estimates of each <i>K</i><sub>s</sub> component derived from the properties at the equivalent oscillation scales, the results outperformed the traditional multiple linear regressions made at the investigation scale, when the same sets of predictors were used. The application of NA-MEMD, moreover, could save the tedious measurements of <i>ϕ</i><sub>e</sub> and <i>ϕ</i>. Excluding these two porosity-related properties, <i>K</i><sub>s</sub> estimates obtained by incorporating NA-MEMD were statistically similar or even better than those involving them before NA-MEMD. These findings demonstrate the great potential of NA-MEMD in untangling scale-dependent relationships of <i>K</i><sub>s</sub> with various processes and hold important implications for future estimations of <i>K</i><sub>s</sub> and other hydraulic properties in the black soil region of northeast China and similar regions.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"213 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139967983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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