To prioritize agricultural research in the United States and to improve its competitiveness globally, Multistate Research Funds (MRFs) were set aside under the Research and Marketing Act of 1946. To implement the act, Agricultural Experiment Station (AES) Directors in the western United States met regularly to evaluate, fund, and review multistate research projects (MRPs), with membership of AES scientists named by the Technical Committee. This article highlights the history of research collaboration in the soil and vadose zone scientific community that was initiated in the western United States. The scientific interactions that started in 1958 with 10 scientists in western land‐grant universities and the USDA to address “Water Movement in Soil” have grown in membership and scope through successive 5‐yr projects. We highlight the value of such collaboration and the scientific advances in soil science and vadose zone hydrology.
{"title":"Western U.S. multistate research project on “water movement in soils”: A retrospective","authors":"J. Hopmans, T. Green, M. Young","doi":"10.1002/vzj2.20245","DOIUrl":"https://doi.org/10.1002/vzj2.20245","url":null,"abstract":"To prioritize agricultural research in the United States and to improve its competitiveness globally, Multistate Research Funds (MRFs) were set aside under the Research and Marketing Act of 1946. To implement the act, Agricultural Experiment Station (AES) Directors in the western United States met regularly to evaluate, fund, and review multistate research projects (MRPs), with membership of AES scientists named by the Technical Committee. This article highlights the history of research collaboration in the soil and vadose zone scientific community that was initiated in the western United States. The scientific interactions that started in 1958 with 10 scientists in western land‐grant universities and the USDA to address “Water Movement in Soil” have grown in membership and scope through successive 5‐yr projects. We highlight the value of such collaboration and the scientific advances in soil science and vadose zone hydrology.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43886806","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}
In this study, the impact of colloid facilitated transport of heavy metals on the overall biogeochemical processes is demonstrated in example Lake Coeurd'Alene sediments. Release and transport of heavy metals (Pb and Zn) on initially sorbed colloidal Fe (hydr)oxide minerals are compared with immobile surfaces under various advective flow velocities. The reactive transport model integrates a coupled biotic reaction network with multiple terminal electron acceptors, including multicomponent diffusion and electrostatic double layer (EDL) treatment effects, illustrating the impact of colloidal transport under competing biogeochemical reaction dynamics for the first time to the authors’ knowledge. The model results illustrate the sensitivity of the results under low‐flow‐velocity conditions. Although enhanced Fe reduction prevails with immobile Fe (hydr)oxide mineral surfaces, the desorbed metal ions with aqueous sulfide complexes are rather “washed out” from the system along with advective transport of solutes, whereas the reductive dissolution of colloidal Fe (hydr)oxides from freshly coming colloidal surfaces results in the accumulation of metal and sulfide ions in the system. The results show that when the potential transport of sorbed contaminants with colloidal particles are ignored, the contaminant concentrations might be underestimated under low‐flow‐velocity conditions, especially around 10−8 or 10−9 m s−1, where the underestimation for the worst case scenario at the lowest bound of low‐flow‐velocity conditions may reach around 90% with depth. On the other hand, this impact may be less significant under cases of higher flow velocity, even around higher limits of low‐velocity environments around 10−7 m s−1, as well as in pure diffusive transport cases.
在这项研究中，胶体促进的重金属运输对整个生物地球化学过程的影响在Coeurd'Alene湖沉积物中得到了证明。在不同的平流速度下，将重金属（Pb和Zn）在最初吸附的胶体氧化铁矿物上的释放和迁移与不动表面进行了比较。反应传输模型集成了具有多个末端电子受体的耦合生物反应网络，包括多组分扩散和静电双层（EDL）处理效应，据作者所知，首次说明了在竞争生物地球化学反应动力学下胶体传输的影响。模型结果说明了低流速条件下结果的敏感性。尽管固定的Fe（hydr）氧化物矿物表面普遍存在增强的Fe还原作用，但具有水性硫化物络合物的解吸金属离子随着溶质的平流传输而从系统中“冲走”，而胶体Fe（hydr）氧化物从新来的胶体表面的还原溶解导致金属和硫化物离子在系统中的积累。结果表明，当忽略胶体颗粒吸附污染物的潜在传输时，在低流速条件下，污染物浓度可能会被低估，尤其是在10−8或10−9 m s−1左右，在低流量条件的最低点，对最坏情况的低估可能会随着深度的增加而达到90%左右。另一方面，在较高流速的情况下，甚至在10−7 m s−1左右的低速环境的较高极限附近，以及在纯扩散传输情况下，这种影响可能不那么显著。
{"title":"Colloidal transport of heavy metals in low‐advective‐velocity environmental systems: Reactive transport model on biogeochemical and hydrodynamic impacts","authors":"Sema Sevinç Şengör, K. Ünlü","doi":"10.1002/vzj2.20233","DOIUrl":"https://doi.org/10.1002/vzj2.20233","url":null,"abstract":"In this study, the impact of colloid facilitated transport of heavy metals on the overall biogeochemical processes is demonstrated in example Lake Coeurd'Alene sediments. Release and transport of heavy metals (Pb and Zn) on initially sorbed colloidal Fe (hydr)oxide minerals are compared with immobile surfaces under various advective flow velocities. The reactive transport model integrates a coupled biotic reaction network with multiple terminal electron acceptors, including multicomponent diffusion and electrostatic double layer (EDL) treatment effects, illustrating the impact of colloidal transport under competing biogeochemical reaction dynamics for the first time to the authors’ knowledge. The model results illustrate the sensitivity of the results under low‐flow‐velocity conditions. Although enhanced Fe reduction prevails with immobile Fe (hydr)oxide mineral surfaces, the desorbed metal ions with aqueous sulfide complexes are rather “washed out” from the system along with advective transport of solutes, whereas the reductive dissolution of colloidal Fe (hydr)oxides from freshly coming colloidal surfaces results in the accumulation of metal and sulfide ions in the system. The results show that when the potential transport of sorbed contaminants with colloidal particles are ignored, the contaminant concentrations might be underestimated under low‐flow‐velocity conditions, especially around 10−8 or 10−9 m s−1, where the underestimation for the worst case scenario at the lowest bound of low‐flow‐velocity conditions may reach around 90% with depth. On the other hand, this impact may be less significant under cases of higher flow velocity, even around higher limits of low‐velocity environments around 10−7 m s−1, as well as in pure diffusive transport cases.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47791288","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}
M. Lakshani, T. C. Chamindu Deepagoda, S. Hamamoto, B. Elberling, W. Fu, Ting Yang, Jun Fan, Xiaoyi Ma, T. Clough, K. Smits, T. Parameswaran, G. S. Sivakumar Babu, H. Chanakya
Soil gas diffusivity (Dp/Do, gas diffusion coefficients in soil and in free air, respectively) and its relation to soil moisture is of great importance for describing and quantifying essential provisional and regulatory functions associated with terrestrial ecosystems such as soil aeration and greenhouse gas (GHG) emissions. Because gas migration in terrestrial soil systems is predominantly diffusion controlled, soil gas diffusivity becomes a fundamental prerequisite to quantify diffusive gas fluxes. Descriptive–predictive models are often used to estimate Dp/Do from easily measurable soil physical properties. Most of the available models take the form of power‐law functions and often tend to mischaracterize soil moisture effects at high moisture regimes. Based on a wide range Dp/Do data available in literature representing both intact and repacked soils, this study developed a novel air‐saturation‐dependent exponential (ASEX) gas diffusivity model to model Dp/Do in relation to soil air saturation. The model variable α, which represents the diffusivity at half air saturation normalized by the same in complete soil air saturation, could potentially differentiate moisture effects on different soil structural states. For specific applications in intact soils, we propose corresponding α values for upper‐limit (α = .6) and lower‐limit (α = .05) estimates of diffusivity, while an average value (α = .3) for general applications in both intact and repacked soils. As expected, our model based on a few a priori measured supportive data showed a better performance over the classical predictive models that do not use such measurements. The new model was further used to derive useful implications to showcase soil density effects on Dp/Do.
{"title":"A new exponential model for predicting soil gas diffusivity with varying degree of saturation","authors":"M. Lakshani, T. C. Chamindu Deepagoda, S. Hamamoto, B. Elberling, W. Fu, Ting Yang, Jun Fan, Xiaoyi Ma, T. Clough, K. Smits, T. Parameswaran, G. S. Sivakumar Babu, H. Chanakya","doi":"10.1002/vzj2.20236","DOIUrl":"https://doi.org/10.1002/vzj2.20236","url":null,"abstract":"Soil gas diffusivity (Dp/Do, gas diffusion coefficients in soil and in free air, respectively) and its relation to soil moisture is of great importance for describing and quantifying essential provisional and regulatory functions associated with terrestrial ecosystems such as soil aeration and greenhouse gas (GHG) emissions. Because gas migration in terrestrial soil systems is predominantly diffusion controlled, soil gas diffusivity becomes a fundamental prerequisite to quantify diffusive gas fluxes. Descriptive–predictive models are often used to estimate Dp/Do from easily measurable soil physical properties. Most of the available models take the form of power‐law functions and often tend to mischaracterize soil moisture effects at high moisture regimes. Based on a wide range Dp/Do data available in literature representing both intact and repacked soils, this study developed a novel air‐saturation‐dependent exponential (ASEX) gas diffusivity model to model Dp/Do in relation to soil air saturation. The model variable α, which represents the diffusivity at half air saturation normalized by the same in complete soil air saturation, could potentially differentiate moisture effects on different soil structural states. For specific applications in intact soils, we propose corresponding α values for upper‐limit (α = .6) and lower‐limit (α = .05) estimates of diffusivity, while an average value (α = .3) for general applications in both intact and repacked soils. As expected, our model based on a few a priori measured supportive data showed a better performance over the classical predictive models that do not use such measurements. The new model was further used to derive useful implications to showcase soil density effects on Dp/Do.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44852872","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}
On the cover: Illustration of depth marks and soil coring holes above and below each mark. The abrupt, wavey boundary between Bt2 and Btk1 (caliche) horizons is visible. See Evett et al., “Methods for downhole soil water sensor calibration–Complications of bulk density and water content variations,” https://doi.org/10.1002/vzj2.20235. Photo by Dr. Steven R. Evett.
封面上:深度标记和每个标记上下的土壤钻孔说明。Bt2和Btk1 (caliche)视界之间的突然波浪边界是可见的。参见Evett等人的“井下土壤水分传感器校准方法——体积密度和含水量变化的复杂性”，https://doi.org/10.1002/vzj2.20235。Steven R. Evett博士摄。
{"title":"Cover Image, Volume 21, Issue 6","authors":"","doi":"10.1002/vzj2.20240","DOIUrl":"https://doi.org/10.1002/vzj2.20240","url":null,"abstract":"<b>On the cover</b>: Illustration of depth marks and soil coring holes above and below each mark. The abrupt, wavey boundary between Bt2 and Btk1 (caliche) horizons is visible. See Evett et al., “Methods for downhole soil water sensor calibration–Complications of bulk density and water content variations,” https://doi.org/10.1002/vzj2.20235. Photo by Dr. Steven R. Evett.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"209 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138541252","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}
{"title":"Editorial: Open Access on the move","authors":"M. Flury, V. Lakshmi, Ning Lu, J. Vanderborght","doi":"10.1002/vzj2.20237","DOIUrl":"https://doi.org/10.1002/vzj2.20237","url":null,"abstract":"","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"5 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50990987","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}
A. Lightfoot, E. Stopelli, M. Berg, M. Brennwald, R. Kipfer
Biogeochemical gas production resulting in free gas phase formation can severely affect groundwater and solute transport in aquifers. Such gas–water interactions are important in aquifers affected by geogenic As, which are commonly associated with biogeochemical CH4 production. Additionally, the influence of aquitards on As concentrations in contaminated aquifers has recently been challenged. These observations prompted the analysis through a heterogeneous aquitard overlying a high CH4−gas‐producing zone of an As‐contaminated aquifer. A sediment core taken through the aquitard was analyzed for noble gases to assess how the aquitard physically contributes to the underlying gas production. Results reveal that the aquitard pore space is unsaturated in two separate layers resulting in hanging pore water constrained by an air‐like gas phase. This interlayering of unsaturated and saturated zones identifies the aquitard's stratigraphy as key in determining hydrostatic pressure—a main control of free gas formation (i.e., CH4) in the underlying aquifer. The partly unsaturated conditions reduce the hydrostatic pressure by 30% compared with fully saturated conditions. To our knowledge, this is the first study applying noble gases to examine the influence of an aquitards physical state on gas production in an underlying aquifer. Further, such partly unsaturated sediment layers of low conductivity might provide preferential pathways for periodic water flow, fostering aquitard–aquifer solute transport. Groundwater samples additionally collected throughout the study site confirm more widespread degassing than previously reported. Up to 90% of the expected atmospheric noble gas concentrations is lost from groundwater immediately below the investigated sediment core.
{"title":"Noble gases in aquitard provide insight into underlying subsurface stratigraphy and free gas formation","authors":"A. Lightfoot, E. Stopelli, M. Berg, M. Brennwald, R. Kipfer","doi":"10.1002/vzj2.20232","DOIUrl":"https://doi.org/10.1002/vzj2.20232","url":null,"abstract":"Biogeochemical gas production resulting in free gas phase formation can severely affect groundwater and solute transport in aquifers. Such gas–water interactions are important in aquifers affected by geogenic As, which are commonly associated with biogeochemical CH4 production. Additionally, the influence of aquitards on As concentrations in contaminated aquifers has recently been challenged. These observations prompted the analysis through a heterogeneous aquitard overlying a high CH4−gas‐producing zone of an As‐contaminated aquifer. A sediment core taken through the aquitard was analyzed for noble gases to assess how the aquitard physically contributes to the underlying gas production. Results reveal that the aquitard pore space is unsaturated in two separate layers resulting in hanging pore water constrained by an air‐like gas phase. This interlayering of unsaturated and saturated zones identifies the aquitard's stratigraphy as key in determining hydrostatic pressure—a main control of free gas formation (i.e., CH4) in the underlying aquifer. The partly unsaturated conditions reduce the hydrostatic pressure by 30% compared with fully saturated conditions. To our knowledge, this is the first study applying noble gases to examine the influence of an aquitards physical state on gas production in an underlying aquifer. Further, such partly unsaturated sediment layers of low conductivity might provide preferential pathways for periodic water flow, fostering aquitard–aquifer solute transport. Groundwater samples additionally collected throughout the study site confirm more widespread degassing than previously reported. Up to 90% of the expected atmospheric noble gas concentrations is lost from groundwater immediately below the investigated sediment core.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42938929","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}
Soil temperature can be influenced by rapidly infiltrating water. Deviations from a uniform soil heat distribution could result from vertical preferential flow (VPF) and lateral subsurface flow (LSF) events. The objective was to identify the effect of infiltration on the soil temperature time series in a lysimeter with forced vertical movement and that in a sloping field to distinguish between VPF and LSF. Wavelet coherence analysis (WCA) was used to analyze soil temperature time series measured in a Colluvic Regosol close to the surface (15‐cm depth) and below (80‐cm depth) in a horizon with possible LSF occurrence. The soil temperatures in these depths were correlated at a daily scale reflecting diurnal fluctuations of air temperatures. A correlation at a monthly scale was similar to the periodicity in the wavelet spectrum of the precipitation from May through October 2015. In this period, soil temperatures at 80‐cm depth changed faster in the lysimeter than in the field, indicating a dominating infiltration‐induced vertical heat movement in the lysimeter. When assuming a temperature‐dampening effect in the sloping field soil by laterally moving temperature‐equilibrated soil water, observed deviations in soil temperature profiles between lysimeter and field could be indicative for LSF in the field. However, LSF occurrence could only be verified by soil water content measurements for single rainfall events in October and May. The analysis was useful to identify qualitatively relevant events in a time series. For quantitative analysis, soil moisture data need to be considered.
{"title":"Exploring the feasibility of using the soil temperature to identify preferential and lateral subsurface flows","authors":"Annelie Ehrhardt, H. Gerke","doi":"10.1002/vzj2.20234","DOIUrl":"https://doi.org/10.1002/vzj2.20234","url":null,"abstract":"Soil temperature can be influenced by rapidly infiltrating water. Deviations from a uniform soil heat distribution could result from vertical preferential flow (VPF) and lateral subsurface flow (LSF) events. The objective was to identify the effect of infiltration on the soil temperature time series in a lysimeter with forced vertical movement and that in a sloping field to distinguish between VPF and LSF. Wavelet coherence analysis (WCA) was used to analyze soil temperature time series measured in a Colluvic Regosol close to the surface (15‐cm depth) and below (80‐cm depth) in a horizon with possible LSF occurrence. The soil temperatures in these depths were correlated at a daily scale reflecting diurnal fluctuations of air temperatures. A correlation at a monthly scale was similar to the periodicity in the wavelet spectrum of the precipitation from May through October 2015. In this period, soil temperatures at 80‐cm depth changed faster in the lysimeter than in the field, indicating a dominating infiltration‐induced vertical heat movement in the lysimeter. When assuming a temperature‐dampening effect in the sloping field soil by laterally moving temperature‐equilibrated soil water, observed deviations in soil temperature profiles between lysimeter and field could be indicative for LSF in the field. However, LSF occurrence could only be verified by soil water content measurements for single rainfall events in October and May. The analysis was useful to identify qualitatively relevant events in a time series. For quantitative analysis, soil moisture data need to be considered.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46380788","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}
S. Evett, G. Marek, P. Colaizzi, K. S. Copeland, Brice B. Ruthardt
Downhole soil volumetric water content (VWC) sensors are used in access tubes to assess the soil water content at multiple depths. If sensor readings are spaced closely enough vertically and are accurate enough, then accurate soil profile water content storage and change in storage can be determined over the depth range of readings, leading to accurate estimates of evapotranspiration (ET) if readings extend to well below the root zone. Even if sensing only covers the active root zone, soil water depletion may be determined well enough to inform irrigation scheduling. While sensor accuracy is dependent on many factors, including the sensor's physical principle of operation, soil‐specific calibration is typically required for good accuracy. In soils with multiple horizons (layers) of different texture, bulk density (BD), or chemical composition, horizon‐specific calibrations may be necessary. We describe methods and equipment used for downhole sensor calibration to typical accuracy of <0.01 m3 m−3 with specific reference to calibration of 10 neutron scattering meters in a soil that required three different horizon‐specific calibrations. Our results contrast with the factory calibration, which would result in a 38‐mm error in water stored in a 1.5‐m deep profile of our soil. We describe variability of measured VWC and BD with depth, distance, and water content and the errors that result from using BD to convert mass basis (g g−1) water content data to VWC data, which can be as much as 35 mm (7.26% underestimation) for soil water storage in a 1.5‐m deep profile of our soil.
{"title":"Methods for downhole soil water sensor calibration—Complications of bulk density and water content variations","authors":"S. Evett, G. Marek, P. Colaizzi, K. S. Copeland, Brice B. Ruthardt","doi":"10.1002/vzj2.20235","DOIUrl":"https://doi.org/10.1002/vzj2.20235","url":null,"abstract":"Downhole soil volumetric water content (VWC) sensors are used in access tubes to assess the soil water content at multiple depths. If sensor readings are spaced closely enough vertically and are accurate enough, then accurate soil profile water content storage and change in storage can be determined over the depth range of readings, leading to accurate estimates of evapotranspiration (ET) if readings extend to well below the root zone. Even if sensing only covers the active root zone, soil water depletion may be determined well enough to inform irrigation scheduling. While sensor accuracy is dependent on many factors, including the sensor's physical principle of operation, soil‐specific calibration is typically required for good accuracy. In soils with multiple horizons (layers) of different texture, bulk density (BD), or chemical composition, horizon‐specific calibrations may be necessary. We describe methods and equipment used for downhole sensor calibration to typical accuracy of <0.01 m3 m−3 with specific reference to calibration of 10 neutron scattering meters in a soil that required three different horizon‐specific calibrations. Our results contrast with the factory calibration, which would result in a 38‐mm error in water stored in a 1.5‐m deep profile of our soil. We describe variability of measured VWC and BD with depth, distance, and water content and the errors that result from using BD to convert mass basis (g g−1) water content data to VWC data, which can be as much as 35 mm (7.26% underestimation) for soil water storage in a 1.5‐m deep profile of our soil.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44062566","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}
D. Linneman, C. Strickland, D. Appriou, M. Rockhold, J. Thomle, J. Szecsody, P. F. Martin, V. Vermeul, R. Mackley, V. Freedman
Performing repeat pore‐fluid sampling over long time‐scales can provide valuable information on unsaturated zone contaminants and their potential flux to ground water. This information can be used to manage groundwater remedies and identify contaminants that need to be sequestered in the vadose zone to minimize flux to ground water. Pore‐water samples are commonly used to obtain contaminant concentrations within the vadose zone, but existing methods are limited as they only provide a single sample at one location and time. The vadose zone advanced monitoring system (VZAMS) has been designed to integrate multiple technologies into a single down‐borehole system that allows for sampling of pore fluids (liquid and gas) to provide information about contamination and hydraulic conditions at multiple depths (∼0.3‐m intervals) within a cased borehole. Testing has been completed at the laboratory scale to verify the sampling elements of VZAMS, including geochemical testing for representative contaminants known to exist at the Hanford Site, located in southeastern Washington State. Physical tests focused on the ability of the sampler to draw fluid under unsaturated conditions. Initial geochemical testing showed that the stainless steel material used with the porous cuff may affect the sampled concentrations of redox‐sensitive contaminants under very dry conditions. Additional laboratory testing demonstrated that the VZAMS components are able to collect representative samples for substances of interest under expected field conditions. In this paper, the design and functionality of a novel instrument are demonstrated in support of subsequent testing in the field.
{"title":"Development of a vadose zone advanced monitoring system: Tools to assess groundwater vulnerability","authors":"D. Linneman, C. Strickland, D. Appriou, M. Rockhold, J. Thomle, J. Szecsody, P. F. Martin, V. Vermeul, R. Mackley, V. Freedman","doi":"10.1002/vzj2.20223","DOIUrl":"https://doi.org/10.1002/vzj2.20223","url":null,"abstract":"Performing repeat pore‐fluid sampling over long time‐scales can provide valuable information on unsaturated zone contaminants and their potential flux to ground water. This information can be used to manage groundwater remedies and identify contaminants that need to be sequestered in the vadose zone to minimize flux to ground water. Pore‐water samples are commonly used to obtain contaminant concentrations within the vadose zone, but existing methods are limited as they only provide a single sample at one location and time. The vadose zone advanced monitoring system (VZAMS) has been designed to integrate multiple technologies into a single down‐borehole system that allows for sampling of pore fluids (liquid and gas) to provide information about contamination and hydraulic conditions at multiple depths (∼0.3‐m intervals) within a cased borehole. Testing has been completed at the laboratory scale to verify the sampling elements of VZAMS, including geochemical testing for representative contaminants known to exist at the Hanford Site, located in southeastern Washington State. Physical tests focused on the ability of the sampler to draw fluid under unsaturated conditions. Initial geochemical testing showed that the stainless steel material used with the porous cuff may affect the sampled concentrations of redox‐sensitive contaminants under very dry conditions. Additional laboratory testing demonstrated that the VZAMS components are able to collect representative samples for substances of interest under expected field conditions. In this paper, the design and functionality of a novel instrument are demonstrated in support of subsequent testing in the field.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47428951","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}
Taohong Cao, D. She, Xiang Zhang, Zhenniang Yang, Guangbo Wang
Soil saturated hydraulic conductivity (Ks) is a key soil hydraulic property that determines the hydrological cycle of check dam–dominated catchment areas. However, Ks data are lacking due to the difficulty of directly measuring this variable in deep soil layers. In this study, 45 soil profiles (0–200 cm) in 15 check dams in three typical watersheds (Xinshui River, Zhujiachuan, and Kuye River) in a hilly gully region on the Chinese Loess Plateau were selected, and a total of 586 soil samples were collected along the soil profiles. Backpropagation neural network (BPNN) and support vector regression (SVR) models based on the genetic algorithm (GA) were tested, and pedotransfer functions for Ks estimation were established for check dams on the Loess Plateau. Basic soil characteristics, such as soil depth, sand, silt, clay, soil organic matter, and bulk density, were adopted as the model inputs to estimate Ks. Combinations of these parameters could be used to suitably estimate Ks, and the models were found to require relatively few soil characteristics to achieve similar accuracy. In comparison to GA‐BPNN, the GA‐SVR model attained good practicability and was more stable in Ks prediction (the geometric mean error ratio was between 0.942 and 1.101; RMSE was between 0.069 and 0.073). Our research can make some contributions to the solution of land restoration and watershed governance on the Chinese Loess Plateau.
{"title":"Pedotransfer functions developed for calculating soil saturated hydraulic conductivity in check dams on the Loess Plateau in China","authors":"Taohong Cao, D. She, Xiang Zhang, Zhenniang Yang, Guangbo Wang","doi":"10.1002/vzj2.20217","DOIUrl":"https://doi.org/10.1002/vzj2.20217","url":null,"abstract":"Soil saturated hydraulic conductivity (Ks) is a key soil hydraulic property that determines the hydrological cycle of check dam–dominated catchment areas. However, Ks data are lacking due to the difficulty of directly measuring this variable in deep soil layers. In this study, 45 soil profiles (0–200 cm) in 15 check dams in three typical watersheds (Xinshui River, Zhujiachuan, and Kuye River) in a hilly gully region on the Chinese Loess Plateau were selected, and a total of 586 soil samples were collected along the soil profiles. Backpropagation neural network (BPNN) and support vector regression (SVR) models based on the genetic algorithm (GA) were tested, and pedotransfer functions for Ks estimation were established for check dams on the Loess Plateau. Basic soil characteristics, such as soil depth, sand, silt, clay, soil organic matter, and bulk density, were adopted as the model inputs to estimate Ks. Combinations of these parameters could be used to suitably estimate Ks, and the models were found to require relatively few soil characteristics to achieve similar accuracy. In comparison to GA‐BPNN, the GA‐SVR model attained good practicability and was more stable in Ks prediction (the geometric mean error ratio was between 0.942 and 1.101; RMSE was between 0.069 and 0.073). Our research can make some contributions to the solution of land restoration and watershed governance on the Chinese Loess Plateau.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"21 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2022-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41608599","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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