Understanding preferential flow (PF) at large scales is critical for improving land management and groundwater (GW) quality. However, limited knowledge of this process, due to soil surface heterogeneity and observational constraints, hampers progress. In this study, we propose estimating effective PF at remote sensing footprint scale (4–9 km) by examining its impact on soil moisture (SM) distribution and shallow groundwater (SGW) table fluctuations (depth 5 m). Effective PF encompasses macropore, funnel, and finger flow pathways influencing SGW table fluctuations. We compiled daily SGW observations (2019–2021) from 19 Continental United States (CONUS) sites through United States Geological Survey. Using inverse modeling in HYDRUS‐1D, SGW data, and climate hazards group infrared precipitation with station data precipitation, we inversely estimated soil hydraulic parameters of the dual‐porosity model (DPM) simulating vertical flow from soil surface to subsurface. Effective PF presence was inferred using three criteria: (1) daily precipitation equal to or exceeding the site‐specific average across multiple (calibration) years, (2) daily observed SGW table increase, and (3) daily difference between observed and DPM simulated SGW tables 50% of the site‐specific root mean square error. Leveraging optimized DPM parameters and associated soil texture, classified PF events, and soil moisture active passive (SMAP L3E) satellite‐based SM, a random forest algorithm with 10‐fold cross validation predicted large‐scale effective PF events. Results indicate seasonal dependence, with spring having the highest occurrence of PF events. The random forest model achieved 98% accuracy in predicting large‐scale PF events, with SMAP SM and saturated hydraulic conductivity (Ks) among the four most impactful variables. Our approach provides a soil hydraulic property, site characteristic, soil texture, and remote sensing‐based generalized tool to analyze large‐scale effective PF.
{"title":"Characterizing large‐scale preferential flow across Continental United States","authors":"Leah Kocian, Binayak P. Mohanty","doi":"10.1002/vzj2.20316","DOIUrl":"https://doi.org/10.1002/vzj2.20316","url":null,"abstract":"Understanding preferential flow (PF) at large scales is critical for improving land management and groundwater (GW) quality. However, limited knowledge of this process, due to soil surface heterogeneity and observational constraints, hampers progress. In this study, we propose estimating effective PF at remote sensing footprint scale (4–9 km) by examining its impact on soil moisture (SM) distribution and shallow groundwater (SGW) table fluctuations (depth 5 m). Effective PF encompasses macropore, funnel, and finger flow pathways influencing SGW table fluctuations. We compiled daily SGW observations (2019–2021) from 19 Continental United States (CONUS) sites through United States Geological Survey. Using inverse modeling in HYDRUS‐1D, SGW data, and climate hazards group infrared precipitation with station data precipitation, we inversely estimated soil hydraulic parameters of the dual‐porosity model (DPM) simulating vertical flow from soil surface to subsurface. Effective PF presence was inferred using three criteria: (1) daily precipitation equal to or exceeding the site‐specific average across multiple (calibration) years, (2) daily observed SGW table increase, and (3) daily difference between observed and DPM simulated SGW tables 50% of the site‐specific root mean square error. Leveraging optimized DPM parameters and associated soil texture, classified PF events, and soil moisture active passive (SMAP L3E) satellite‐based SM, a random forest algorithm with 10‐fold cross validation predicted large‐scale effective PF events. Results indicate seasonal dependence, with spring having the highest occurrence of PF events. The random forest model achieved 98% accuracy in predicting large‐scale PF events, with SMAP SM and saturated hydraulic conductivity (<jats:italic>K</jats:italic><jats:sub>s</jats:sub>) among the four most impactful variables. Our approach provides a soil hydraulic property, site characteristic, soil texture, and remote sensing‐based generalized tool to analyze large‐scale effective PF.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"170 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139968685","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 water‐stressed regions of the world, the inundation of working landscapes to replenish aquifers—known as flood‐managed aquifer recharge (flood‐MAR)—has become a valuable tool for sustainable groundwater management. Due to their diverse land use histories, however, many potential recharge sites host nonpoint source contaminants (such as salts, pesticides, and fertilizers) within the vadose zone that may flush to groundwater during recharge operations. To identify the controls on contaminant migration, we perform stochastic simulations of flood‐MAR through a heterogeneous alluvial aquifer and apply transient particle tracking to evaluate conservative and reactive contaminant transport over 80 years of recharge operations. With semi‐annual recharge events, the water table begins to rise 0.13–1.84 years after the first inundation event while solutes take much longer (11 to 80 years) to transit the 45‐m thick unsaturated zone. We derive a parametric expression for the ratio of celerity (or rate of pressure transmission) to velocity of the flood‐MAR wetting front and show that this simplified expression agrees with values calculated from heterogeneous model simulations. Slow solute velocities (0.25–1.75 m year−1) allow for significant contaminant removal through denitrification, but the contaminant plume experiences minimal dispersion or dilution over this time, reaching the water table as a sharp front. Our results suggest that minimizing groundwater velocity and maximizing groundwater celerity during flood‐MAR should optimize increases in water supply while limiting water quality degradation.
{"title":"Transport, dispersion, and degradation of nonpoint source contaminants during flood‐managed aquifer recharge","authors":"Zach Perzan, Kate Maher","doi":"10.1002/vzj2.20307","DOIUrl":"https://doi.org/10.1002/vzj2.20307","url":null,"abstract":"In water‐stressed regions of the world, the inundation of working landscapes to replenish aquifers—known as flood‐managed aquifer recharge (flood‐MAR)—has become a valuable tool for sustainable groundwater management. Due to their diverse land use histories, however, many potential recharge sites host nonpoint source contaminants (such as salts, pesticides, and fertilizers) within the vadose zone that may flush to groundwater during recharge operations. To identify the controls on contaminant migration, we perform stochastic simulations of flood‐MAR through a heterogeneous alluvial aquifer and apply transient particle tracking to evaluate conservative and reactive contaminant transport over 80 years of recharge operations. With semi‐annual recharge events, the water table begins to rise 0.13–1.84 years after the first inundation event while solutes take much longer (11 to 80 years) to transit the 45‐m thick unsaturated zone. We derive a parametric expression for the ratio of celerity (or rate of pressure transmission) to velocity of the flood‐MAR wetting front and show that this simplified expression agrees with values calculated from heterogeneous model simulations. Slow solute velocities (0.25–1.75 m year<jats:sup>−1</jats:sup>) allow for significant contaminant removal through denitrification, but the contaminant plume experiences minimal dispersion or dilution over this time, reaching the water table as a sharp front. Our results suggest that minimizing groundwater velocity and maximizing groundwater celerity during flood‐MAR should optimize increases in water supply while limiting water quality degradation.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"21 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139953121","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}
Quirijn de Jong van Lier, Marina Luciana Abreu de Melo, Everton Alves Rodrigues Pinheiro
The uncertainty in soil hydraulic parameters is often not taken into account in process-based hydrological modeling. Performing runs with 104 stochastic parameter realizations, we evaluated the propagation of uncertainty in the Van Genuchten–Mualem (VGM) parameters into estimates of the threshold values of soil water content used to calculate the total and readily available water, and on the long-term (30 years) simulations of evaporation, transpiration, bottom flux, and runoff by the SWAP hydrological model. The simulated scenarios included weather data from a location in southeast Brazil and seven soils from the same region cropped with maize, comprising a wide range of texture classes. The results showed that uncertainties in VGM parameters affect the estimates of total and readily available water. Water balance components obtained by a deterministic simulation with average VGM parameters did not always agree with the average or median of stochastic simulations, and stochastic simulations including parameter uncertainties should be preferred. Variations in yearly rainfall characteristics were more important for bottom flux and evaporation, while transpiration and runoff were more strongly influenced by the variations in soil hydraulic properties.
{"title":"Stochastic analysis of plant available water estimates and soil water balance components simulated by a hydrological model","authors":"Quirijn de Jong van Lier, Marina Luciana Abreu de Melo, Everton Alves Rodrigues Pinheiro","doi":"10.1002/vzj2.20306","DOIUrl":"https://doi.org/10.1002/vzj2.20306","url":null,"abstract":"The uncertainty in soil hydraulic parameters is often not taken into account in process-based hydrological modeling. Performing runs with 10<sup>4</sup> stochastic parameter realizations, we evaluated the propagation of uncertainty in the Van Genuchten–Mualem (VGM) parameters into estimates of the threshold values of soil water content used to calculate the total and readily available water, and on the long-term (30 years) simulations of evaporation, transpiration, bottom flux, and runoff by the SWAP hydrological model. The simulated scenarios included weather data from a location in southeast Brazil and seven soils from the same region cropped with maize, comprising a wide range of texture classes. The results showed that uncertainties in VGM parameters affect the estimates of total and readily available water. Water balance components obtained by a deterministic simulation with average VGM parameters did not always agree with the average or median of stochastic simulations, and stochastic simulations including parameter uncertainties should be preferred. Variations in yearly rainfall characteristics were more important for bottom flux and evaporation, while transpiration and runoff were more strongly influenced by the variations in soil hydraulic properties.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"287 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139755256","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}
Yanan Huang, Jaivime Evaristo, Zhi Li, Kwok P. Chun, Edwin H. Sutanudjaja, M. Bayani Cardenas, Marc F. P. Bierkens, James W. Kirchner, Martinus Th. van Genuchten
Tritium present in deep vadose zones is a useful tracer for estimating groundwater recharge, but its full utility is constrained by not knowing where and for how long the tritium tracing method remains applicable. We obtained 44 tritium profiles from 17 globally distributed sites with vadose zone thicknesses of 12–624 m and used transport models to estimate the number of years that tritium may still be useful. Results show that the method may still be usable for 26 of 44 soil profiles surveyed, mainly in China, Australia, the United States, South Africa, and Senegal, with a remaining useful period of between 6 and 83 years. We also developed a statistical model that uses outputs from a hydrological model to predict the applicability of the tritium tracing method. Global implementation of the statistical model showed that the method remains usable at 20% of Earth's land mass (excluding Antarctica and Greenland) over the next few decades.
{"title":"The nature and extent of bomb tritium remaining in deep vadose zone: A synthesis and prognosis","authors":"Yanan Huang, Jaivime Evaristo, Zhi Li, Kwok P. Chun, Edwin H. Sutanudjaja, M. Bayani Cardenas, Marc F. P. Bierkens, James W. Kirchner, Martinus Th. van Genuchten","doi":"10.1002/vzj2.20304","DOIUrl":"https://doi.org/10.1002/vzj2.20304","url":null,"abstract":"Tritium present in deep vadose zones is a useful tracer for estimating groundwater recharge, but its full utility is constrained by not knowing where and for how long the tritium tracing method remains applicable. We obtained 44 tritium profiles from 17 globally distributed sites with vadose zone thicknesses of 12–624 m and used transport models to estimate the number of years that tritium may still be useful. Results show that the method may still be usable for 26 of 44 soil profiles surveyed, mainly in China, Australia, the United States, South Africa, and Senegal, with a remaining useful period of between 6 and 83 years. We also developed a statistical model that uses outputs from a hydrological model to predict the applicability of the tritium tracing method. Global implementation of the statistical model showed that the method remains usable at 20% of Earth's land mass (excluding Antarctica and Greenland) over the next few decades.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"36 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139514966","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 moisture (SM) is an important component for many applications in agriculture, hydrology, meteorology, and ecology. In past decades, passive/active microwave sensors onboard Earth observation satellites are utilized to obtain SM estimates from radiometer or radar observations. In this study, the Soil Moisture and Ocean Salinity (SMOS) Level 3 daily SM retrievals at 25-km spatial resolution between 2010 and 2021 were downscaled through an apparent thermal inertia principle-based algorithm. The 1-km downscaled SMOS SM retrievals were validated by in situ measurements from 635 sites of 19 SM networks in the world, which were acquired from the International Soil Moisture Network and Texas Soil Observation Network. Additionally, the validation results of the SMOS SM products were compared with those of the Soil Moisture Active Passive (SMAP) global Level 2 enhanced SM products at 1-km downscaled and original 9-km resolution in 2015–2021. It shows that the downscaled SMOS SM data have an overall improved accuracy and outperform the coarse-resolution 25-km data, with a lower unbiased Root Mean Squared Error of 0.114 m3/m3 on average.
{"title":"Validation of downscaled 1-km SMOS and SMAP soil moisture data in 2010–2021","authors":"Bin Fang, Venkataraman Lakshmi, Runze Zhang","doi":"10.1002/vzj2.20305","DOIUrl":"https://doi.org/10.1002/vzj2.20305","url":null,"abstract":"Soil moisture (SM) is an important component for many applications in agriculture, hydrology, meteorology, and ecology. In past decades, passive/active microwave sensors onboard Earth observation satellites are utilized to obtain SM estimates from radiometer or radar observations. In this study, the Soil Moisture and Ocean Salinity (SMOS) Level 3 daily SM retrievals at 25-km spatial resolution between 2010 and 2021 were downscaled through an apparent thermal inertia principle-based algorithm. The 1-km downscaled SMOS SM retrievals were validated by in situ measurements from 635 sites of 19 SM networks in the world, which were acquired from the International Soil Moisture Network and Texas Soil Observation Network. Additionally, the validation results of the SMOS SM products were compared with those of the Soil Moisture Active Passive (SMAP) global Level 2 enhanced SM products at 1-km downscaled and original 9-km resolution in 2015–2021. It shows that the downscaled SMOS SM data have an overall improved accuracy and outperform the coarse-resolution 25-km data, with a lower unbiased Root Mean Squared Error of 0.114 m<sup>3</sup>/m<sup>3</sup> on average.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"27 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139499917","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}
Judith Robinson, Timothy Johnson, Jonathan Thomle, Joaquin Cambeiro, Kelsey Peta, Piyoosh Jaysaval, Rob Mackley
Surface electrical resistivity tomography (ERT) was used at a waste site to monitor vadose zone changes in electrical properties as a proxy for contaminant flux over a span of 17 years. The BC Cribs and Trenches (BCCT) site at the Hanford site contains 20 disposal trenches and six disposal cribs. Wastes include a large inventory of technetium-99 and large masses of nitrate and uranium-238. ERT data were collected along 41 profiles in 2005 to characterize regions of elevated bulk electrical conductivity (BEC) associated with past liquid waste discharges. Previous analyses performed on samples from four boreholes showed a high correlation between nitrate concentration and BEC. In 2022, ERT data were re-collected along the same profiles and six additional profiles in an area not previously surveyed. Compared to background uncontaminated areas, BEC was higher in contaminated areas at the waste sites. Given the correlation between nitrate concentration and BEC previously found at this site, ERT images show the spatial distribution and relative ionic concentration of vadose zone contaminants at BCCT. Between 2005 and 2022, ERT difference images showed a decrease in BEC surrounding most waste sites, with exceptions where there were known anthropogenic surface changes. An evaluation of recharge-driven nitrate migration using synthetic flow and transport simulations showed that downward migration causes a decrease in BEC from the decrease in ionic strength at the trailing end of the plume where contaminants migrated downward. From this, we interpret ERT difference images as showing the predominant regions of downward ion flux.
{"title":"Interpretation of large-scale, long-term electrical geophysical monitoring guided by a process simulation","authors":"Judith Robinson, Timothy Johnson, Jonathan Thomle, Joaquin Cambeiro, Kelsey Peta, Piyoosh Jaysaval, Rob Mackley","doi":"10.1002/vzj2.20303","DOIUrl":"https://doi.org/10.1002/vzj2.20303","url":null,"abstract":"Surface electrical resistivity tomography (ERT) was used at a waste site to monitor vadose zone changes in electrical properties as a proxy for contaminant flux over a span of 17 years. The BC Cribs and Trenches (BCCT) site at the Hanford site contains 20 disposal trenches and six disposal cribs. Wastes include a large inventory of technetium-99 and large masses of nitrate and uranium-238. ERT data were collected along 41 profiles in 2005 to characterize regions of elevated bulk electrical conductivity (BEC) associated with past liquid waste discharges. Previous analyses performed on samples from four boreholes showed a high correlation between nitrate concentration and BEC. In 2022, ERT data were re-collected along the same profiles and six additional profiles in an area not previously surveyed. Compared to background uncontaminated areas, BEC was higher in contaminated areas at the waste sites. Given the correlation between nitrate concentration and BEC previously found at this site, ERT images show the spatial distribution and relative ionic concentration of vadose zone contaminants at BCCT. Between 2005 and 2022, ERT difference images showed a decrease in BEC surrounding most waste sites, with exceptions where there were known anthropogenic surface changes. An evaluation of recharge-driven nitrate migration using synthetic flow and transport simulations showed that downward migration causes a decrease in BEC from the decrease in ionic strength at the trailing end of the plume where contaminants migrated downward. From this, we interpret ERT difference images as showing the predominant regions of downward ion flux.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"164 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139476287","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}
Y. Pachepsky, A. Yakirevich, A. A. Ponizovsky, N. Gummatov
The osmotic potential in soil solutions decreases as salinity increases, and plants cannot take up enough soil water. Therefore, the osmotic potential of soil solutions can serve as an important metric of plant growth conditions in regions affected by soil salinization. Measurements of osmotic potential are labor and time consuming. This work aimed to determine more readily available soil salinity metrics to estimate the osmotic potential in soil solutions. A model to compute the osmotic potential from soil solution composition was developed and validated with data from the U.S. states of Washington, Oregon, Colorado, and Idaho. The mean relative error was 7%. Then, this model was applied to 230 datasets on soil solutions from various salinity-affected regions of Eurasia. The correlation coefficient between logarithms of concentration of highly soluble (not including carbonates and sulfates of calcium and magnesium) in soil solutions at saturation and logarithms of osmotic potential values was above 0.99. The concentration of highly soluble salts in soil solution at saturation was chosen as the predictor of the osmotic potential. It was used to develop nomograms for evaluating the salinity-related yield loss for major field crops, vegetables, and fruits. This work is a part of the Vadose Zone Journal tribute to the scientific legacy of Martinus van Genuchten, who championed the use of the osmotic potential for better quantification of crop salt tolerance at the macroscale and provided invaluable contributions to modeling soil salinity development and mitigation as a part of the global struggle for food security.
{"title":"The osmotic potential of soil solutions in salt tolerance studies: Following M. Th. van Genuchten's innovation","authors":"Y. Pachepsky, A. Yakirevich, A. A. Ponizovsky, N. Gummatov","doi":"10.1002/vzj2.20299","DOIUrl":"https://doi.org/10.1002/vzj2.20299","url":null,"abstract":"The osmotic potential in soil solutions decreases as salinity increases, and plants cannot take up enough soil water. Therefore, the osmotic potential of soil solutions can serve as an important metric of plant growth conditions in regions affected by soil salinization. Measurements of osmotic potential are labor and time consuming. This work aimed to determine more readily available soil salinity metrics to estimate the osmotic potential in soil solutions. A model to compute the osmotic potential from soil solution composition was developed and validated with data from the U.S. states of Washington, Oregon, Colorado, and Idaho. The mean relative error was 7%. Then, this model was applied to 230 datasets on soil solutions from various salinity-affected regions of Eurasia. The correlation coefficient between logarithms of concentration of highly soluble (not including carbonates and sulfates of calcium and magnesium) in soil solutions at saturation and logarithms of osmotic potential values was above 0.99. The concentration of highly soluble salts in soil solution at saturation was chosen as the predictor of the osmotic potential. It was used to develop nomograms for evaluating the salinity-related yield loss for major field crops, vegetables, and fruits. This work is a part of the Vadose Zone Journal tribute to the scientific legacy of Martinus van Genuchten, who championed the use of the osmotic potential for better quantification of crop salt tolerance at the macroscale and provided invaluable contributions to modeling soil salinity development and mitigation as a part of the global struggle for food security.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"50 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139414058","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}
Martin Zanutel, Sarah Garré, Patrick Sanglier, Charles Bielders
Besides its carbon sequestration potential, biochar application generally improves soil physical properties, but the magnitude of its impact and the underlying mechanisms remain debated and depend on soil type, biochar application rate, and age. The objective was therefore to determine the effect of biochar application rate and age on physical properties of agricultural soils in a temperate climate. On a silt loam and a sandy loam soils, we compared the physical properties of fresh biochar (1% and 2% w/w) or century-old biochar (0.5%–1% w/w; 19th-century kiln sites)-enriched soil samples with biochar-free soil samples. Biochar pore network characteristics were determined using helium pycnometry, mercury intrusion porosimetry, scanning electron microscopy observation, and electron dispersive X-ray spectrometry, whereas location of biochar particles within soil structure was analyzed using optical microscopy observations. Fresh biochar application decreased bulk density by 16.8% and increased saturated water content by 16.0% and macroporosity by 78.8%. These effects were attributed to soil structure improvement rather than to biochar porosity. Soil type and biochar application rate had a limited impact. In the long-term, biochar effects were mostly nonsignificant, which might result from its fairly low content in kiln sites and from the clogging of its internal porosity by clay particles. Biochar was thus able to improve some soil physical properties in the short-term, but these effects could no longer be detected in the very long-term. Further investigating the time rate of change in soil physical properties over several decades following biochar additions to soil would therefore seem particularly relevant.
{"title":"Biochar modifies soil physical properties mostly through changes in soil structure rather than through its internal porosity","authors":"Martin Zanutel, Sarah Garré, Patrick Sanglier, Charles Bielders","doi":"10.1002/vzj2.20301","DOIUrl":"https://doi.org/10.1002/vzj2.20301","url":null,"abstract":"Besides its carbon sequestration potential, biochar application generally improves soil physical properties, but the magnitude of its impact and the underlying mechanisms remain debated and depend on soil type, biochar application rate, and age. The objective was therefore to determine the effect of biochar application rate and age on physical properties of agricultural soils in a temperate climate. On a silt loam and a sandy loam soils, we compared the physical properties of fresh biochar (1% and 2% w/w) or century-old biochar (0.5%–1% w/w; 19th-century kiln sites)-enriched soil samples with biochar-free soil samples. Biochar pore network characteristics were determined using helium pycnometry, mercury intrusion porosimetry, scanning electron microscopy observation, and electron dispersive X-ray spectrometry, whereas location of biochar particles within soil structure was analyzed using optical microscopy observations. Fresh biochar application decreased bulk density by 16.8% and increased saturated water content by 16.0% and macroporosity by 78.8%. These effects were attributed to soil structure improvement rather than to biochar porosity. Soil type and biochar application rate had a limited impact. In the long-term, biochar effects were mostly nonsignificant, which might result from its fairly low content in kiln sites and from the clogging of its internal porosity by clay particles. Biochar was thus able to improve some soil physical properties in the short-term, but these effects could no longer be detected in the very long-term. Further investigating the time rate of change in soil physical properties over several decades following biochar additions to soil would therefore seem particularly relevant.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"16 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053112","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}
Yongwei Fu, Behzad Ghanbarian, Robert Horton, Joshua Heitman
The heat transfer and water retention in soils, governed by soil thermal conductivity (λ) and soil water retention curve (SWRC), are coupled. Soil water content (θ) significantly affects λ. Several models have been developed to describe λ(θ) relationships for unsaturated soils. Ghanbarian and Daigle presented a percolation-based effective-medium approximation (P-EMA) for λ(θ) with two parameters: scaling exponent (ts) and critical water content (θc). In this study, we explored the new insights into the correlation between soil thermal conductivity and water retention using the P-EMA and van Genuchten models. The θc was strongly correlated to selected soil hydraulic and physical properties, such as water contents at wilting point (θpwp), inflection point (θi), and hydraulic continuity (θhc) determined from measured SWRCs for a 23-soil calibration dataset. The established relationships were then evaluated on a seven-soil validation dataset to estimate θc. Results confirmed their robustness with root mean square error ranging from 0.011 to 0.015 cm3 cm−3, MAE ranging from 0.008 to 0.013 cm3 cm−3, and R2 of 0.98. Further discussion investigated the underlying mechanism for the correlation between θc with θhc which dominate both heat transfer and water flow. More importantly, this study revealed the possibility to further investigate the general relationship between λ(θ) and SWRC data in the future.
{"title":"New insights into the correlation between soil thermal conductivity and water retention in unsaturated soils","authors":"Yongwei Fu, Behzad Ghanbarian, Robert Horton, Joshua Heitman","doi":"10.1002/vzj2.20297","DOIUrl":"https://doi.org/10.1002/vzj2.20297","url":null,"abstract":"The heat transfer and water retention in soils, governed by soil thermal conductivity (λ) and soil water retention curve (SWRC), are coupled. Soil water content (θ) significantly affects λ. Several models have been developed to describe λ(θ) relationships for unsaturated soils. Ghanbarian and Daigle presented a percolation-based effective-medium approximation (P-EMA) for λ(θ) with two parameters: scaling exponent (<i>t</i><sub>s</sub>) and critical water content (θ<sub>c</sub>). In this study, we explored the new insights into the correlation between soil thermal conductivity and water retention using the P-EMA and van Genuchten models. The θ<sub>c</sub> was strongly correlated to selected soil hydraulic and physical properties, such as water contents at wilting point (θ<sub>pwp</sub>), inflection point (θ<sub>i</sub>), and hydraulic continuity (θ<sub>hc</sub>) determined from measured SWRCs for a 23-soil calibration dataset. The established relationships were then evaluated on a seven-soil validation dataset to estimate θ<sub>c</sub>. Results confirmed their robustness with root mean square error ranging from 0.011 to 0.015 cm<sup>3</sup> cm<sup>−3</sup>, MAE ranging from 0.008 to 0.013 cm<sup>3</sup> cm<sup>−3</sup>, and <i>R</i><sup>2</sup> of 0.98. Further discussion investigated the underlying mechanism for the correlation between θ<sub>c</sub> with θ<sub>hc</sub> which dominate both heat transfer and water flow. More importantly, this study revealed the possibility to further investigate the general relationship between λ(θ) and SWRC data in the future.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"37 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053121","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}
Mario Feifel, Wolfgang Durner, Tobias L. Hohenbrink, Andre Peters
Climate change will lead to prolonged droughts in various regions of the world, which may significantly affect agricultural production. This is particularly problematic for soils with low water retention capacity, which cannot store sufficient water for crops. In this paper, we investigate how a change in the water-holding capacity of the soil material, as could be achieved by increasing the soil organic carbon (SOC) amount, affects the components of the soil water balance (evaporation, transpiration, and groundwater recharge). Specifically, we state the hypothesis that an increased water-holding capacity in a shallow soil layer, as it is achieved through SOC enrichment at the soil surface, will result in more water being stored near the soil surface and lost to unproductive evaporation, thereby reducing the amount of water available to plants and groundwater recharge. The hypothesis was tested by numerical simulations, employing the Hydrus-1D program package to model the water balance in a soil–plant–atmosphere system for an arable crop in hydrologically contrasting years. The study considered soils with varying textures and different depths of a soil layer with increased SOC content. The soil hydraulic properties (SHP) of the soil material, including the effect of SOC on the SHP, were determined using a recently developed pedotransfer model based on data from over 500 samples. We showed that both the improved water retention by SOC and its vertical distribution affect the soil water balance in a complex manner. In sandy soils, increasing the water-holding capacity in shallow layers up to 0.1 m led to enhanced evaporation and thus a decrease in water availability for crops. However, deeper incorporated SOC could ameliorate these negative effects. Our findings suggest that not only the amount but also the vertical SOC distribution should be considered if enrichment of SOC shall be applied to mitigate the effect of droughts.
{"title":"Effects of improved water retention by increased soil organic matter on the water balance of arable soils: A numerical analysis","authors":"Mario Feifel, Wolfgang Durner, Tobias L. Hohenbrink, Andre Peters","doi":"10.1002/vzj2.20302","DOIUrl":"https://doi.org/10.1002/vzj2.20302","url":null,"abstract":"Climate change will lead to prolonged droughts in various regions of the world, which may significantly affect agricultural production. This is particularly problematic for soils with low water retention capacity, which cannot store sufficient water for crops. In this paper, we investigate how a change in the water-holding capacity of the soil material, as could be achieved by increasing the soil organic carbon (SOC) amount, affects the components of the soil water balance (evaporation, transpiration, and groundwater recharge). Specifically, we state the hypothesis that an increased water-holding capacity in a shallow soil layer, as it is achieved through SOC enrichment at the soil surface, will result in more water being stored near the soil surface and lost to unproductive evaporation, thereby reducing the amount of water available to plants and groundwater recharge. The hypothesis was tested by numerical simulations, employing the Hydrus-1D program package to model the water balance in a soil–plant–atmosphere system for an arable crop in hydrologically contrasting years. The study considered soils with varying textures and different depths of a soil layer with increased SOC content. The soil hydraulic properties (SHP) of the soil material, including the effect of SOC on the SHP, were determined using a recently developed pedotransfer model based on data from over 500 samples. We showed that both the improved water retention by SOC and its vertical distribution affect the soil water balance in a complex manner. In sandy soils, increasing the water-holding capacity in shallow layers up to 0.1 m led to enhanced evaporation and thus a decrease in water availability for crops. However, deeper incorporated SOC could ameliorate these negative effects. Our findings suggest that not only the amount but also the vertical SOC distribution should be considered if enrichment of SOC shall be applied to mitigate the effect of droughts.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":"16 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053281","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：