Displays

Near surface hydrological processes whereby moisture exchange occurs between the vadose zone and above-ground weather systems occur on daily, seasonal, and long-term cycles. Well-controlled laboratory studies of near surface moisture migration are often limited due to number of measurement points of moisture content and pore pressure. This presentation will describe experimental and digital image analysis techniques incorporating a refractive index matched soil-pore fluid combination that increase spatial resolution of saturation measurements by over 6 orders of magnitude. The refractive index matched material changes color from black (Saturation=1) to white (Saturation=0) allowing for saturation measurements at the digital pixel scale. This visualization technique allows for direct observation of flow effects which affect boundary measurements and local flow mechanisms. The capabilities of unsaturated transparent soil are incorporated in a 2D infiltration apparatus to examine the influence of confined air on infiltration. 2D experiments agree with previous column infiltration results showing air confinement decreases infiltration rate by more than one half. The 2D apparatus allows a clear unstable wetting front to develop, visualization of dynamic moisture migration within the transmission zone. In addition, the high spatial resolution saturation measurements show detectable influence of thin heterogeneities on wetting front migration and the influence of flow direction on saturation distribution. The high-resolution saturation measurements will allow for calibration of computational models multi-phase flow and open up new insight into near surface processes to improve water balance calculations and soil-structure-climate interactions.

How to cite: Siemens, G., Oldroyd, C., and Beddoe, R.: Infiltration experiments with ultra-high spatial and temporal resolution of saturation measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20212, https://doi.org/10.5194/egusphere-egu2020-20212, 2020.

Classic soil physics relies heavily on the concept of representative elementary volume (REV), which is necessary to perform upscaling from the studied soil samples and parameterize continuum scale hydrological models (e.g., based on Richards equation). In this paper we explore the boundaries of the classic REV concept and conventional representativity studies that claim REV for a given physical property if its values converge to a steady value with increasing sample’s volume. We chose two conventional undisturbed soil samples from Ah and B horizons and performed pore-scale flow simulations based on their X-ray microtomography scans. The volumes of the simulation domains were 729 million of voxels with a physical volume within the order of magnitude of the whole soil core. Based on 3D pore geometry images and resulting flow velocity and pressure fields we performed REV analysis for saturated hydraulic conductivity and porosity. To further facilitate the REV analysis, we also evaluated the stationarity of pore structures by computing directional correlation functions for studied images. We concluded that neither of the studied samples can be considered to be representative due to its structural non-stationarity, which reflects on the behavior of Ksat values within the subcubes of different volume within the samples. In this contribution we extensively discuss the implications of such results. While it was possible to show that studied soil samples are not REVs for saturated hydraulic conductivity, we were unable to establish any relevant domain length scale. The latter may require tensorial flow property analysis with correct boundary conditions (Gerke et al., 2019), multi-scale soil structure imaging (Gerke et al., 2015; Karsanina et al., 2018; Karsanina and Gerke, 2018) and pore-scale simulations on fused multi-scale images (Miao et al., 2017; Gerke et al., 2018).

This work was supported by Russian Foundation for Basic Research grant 20-54-12030 ННИО_а and 18-34-20131 мол_а_вед.

References:

Karsanina, M. V., Gerke, K. M., Skvortsova, E. B., Ivanov, A. L., & Mallants, D. (2018). Enhancing image resolution of soils by stochastic multiscale image fusion. Geoderma, 314, 138-145.

Gerke, K. M., Karsanina, M. V., & Mallants, D. (2015). Universal stochastic multiscale image fusion: an example application for shale rock. Scientific reports, 5, 15880.

Gerke, K. M., Vasilyev, R. V., Khirevich, S., Collins, D., Karsanina, M. V., Sizonenko, T. O., Korost D.V., Lamontagne S., & Mallants, D. (2018). Finite-difference method Stokes solver (FDMSS) for 3D pore geometries: Software development, validation and case studies. Computers & Geosciences, 114, 41-58

Karsanina, M. V., & Gerke, K. M. (2018). Hierarchical Optimization: Fast and Robust Multiscale Stochastic Reconstructions with Rescaled Correlation Functions. Physical Review Letters, 121(26), 265501.

Miao, X., Gerke, K. M., & Sizonenko, T. O. (2017). A new way to parameterize hydraulic conductances of pore elements: A step towards creating pore-networks without pore shape simplifications. Advances in Water Resources, 105, 162-172.

Gerke, K. M., Karsanina, M. V., & Katsman, R. (2019). Calculation of tensorial flow properties on pore level: Exploring the influence of boundary conditions on the permeability of three-dimensional stochastic reconstructions. Physical Review E, 100(5), 053312.

How to cite: Gerke, K. and Karsanina, M.: How representative is the conventional undisturbed soil core sample in terms of fllow properties?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10841, https://doi.org/10.5194/egusphere-egu2020-10841, 2020.

Increase in impermeable area and frequency of intense rainfall cause flooding damages in urban areas. Permeable Interlocking Concrete Paver (PICP) system, which is a composite system comprised of soils and blocks, is considered as one of the solutions to improve the urban water environment, and its applications are increasing rapidly worldwide. It is important to evaluate the initial permeability and its reduction due to clogging. In this study, the permeability and effect of clogging were evaluated based on experimental methods developed. The equivalent permeability and its degradation of PICP systems were successfully evaluated using the prodecure developed, and the equation for equivalent permeability presented quite a good agreement with the experimental results.

ACKNOWLEDGEMENT : The authors would like to thank the Ministry of Land, Infrastructure, and Transport of Korean government for the grant from Technology Advancement Research Program (grant no. 20CTAP-C152124-02) and Basic Science Research Program (grant no. 2017R1D1A3B03034563) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education.

How to cite: Ahn, J. and Lee, Y.: Experimental Evaluation of Equivalent Permeability for Permeable Interlocking Concrete Paver (Soil-Block) Composite System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7434, https://doi.org/10.5194/egusphere-egu2020-7434, 2020.

The multidisciplinary research project SWAT - Subsurface Water quality and Agricultural pracTices monitoring - has been set up to assess pesticides contamination risks for groundwater in the hills of Prosecco in the north-east of Italy. The unconfined aquifer underneath the typical Glera grape-variety vineyards of Valdobbiadene and Conegliano is used as water supply resource for human consumption. The principal aim of the project SWAT is to obtain a thorough information on the impact of contaminants coming from agricultural practices and infiltrating in the soil of well protection areas. Based on specifically designed field experiments, a study on water and solutes infiltration process is developed to understand the movement and evolution of chemical species in the vadose zone. A one-dimensional transport model for unsaturated media (BRTSim - Maggi, 2015) is used to simulate solute infiltration and estimate the soil hydraulic parameters. Monitoring activities started in November 2018 in two experimental sites (the Settolo site in Valdobbiadene and the Colnù site in Conegliano) near supply wells surrounded by vineyards. A mixture of Bromide and Glyphosate was identically applied on two parcels of 25 m² for each experimental site to obtain information about spatial heterogeneity and to collect independently water and soil quality measurements. Porous cups, for the collection of infiltrating water, and capacitive sensors, to gauge temperature and Volumetric Water Content (VWC), were installed beneath the sectors at three depths (-0.1, -0.3, -0.7 m). In each site meteorological station provides hydrological data. At first, laboratory analysis on soil samples collected at the same depths gave a vertical distribution of the sector-specific soil texture that was used as input for Rosetta to obtain initial estimations of retention curve behaviour and the saturated hydraulic conductivity. These data allowed us to develop an open-loop simulation using the early meteorological observations as hydrological forcing. As the laboratory analysis on soil and water samples proceed and the number of in-situ measurements increases, different data windows are tested to improve the performances of the calibration procedure performed using PEST. In all tests a spin-up procedure is applied to mitigate the dependency of the results on the imposed initial data by repeating the first month of hydrological forcing three times. The results of the transport model using Rosetta parameters are already satisfactory in terms of VWC trends even if they are considerably shifted respect to the measured values. The calibration reduces the gap between model results and observations, but the behaviour seems to get worse in dry conditions. Improvements are achieved in the upper layer (-0.3 m) applying evapotranspiration along the root zone. The Bromide simulations agree with the infiltration behaviour: its movement is well represented up to -0.3 m, while at -0.7 m the observed values are overestimated. Ongoing investigations on the glyphosate dispersion process show limited infiltrating mass in the water collected samples.

How to cite: Costa, L., Mazzega Ciamp, S., Cardinali, A., Carretta, L., Dal Ferro, N., Mencaroni, M., Morari, F., Zanin, G., and Salandin, P.: Numerical assessment of chemical species infiltration in the Prosecco area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14653, https://doi.org/10.5194/egusphere-egu2020-14653, 2020.

Hydrophobic soils and sediments have gained significant interest in soil science due to negatively influencing biomass production and as drivers of landslides and enhanced erosion. Whilst natural and fire-induced soil water repellency have been studied, little work has considered how the sediment-water interaction with naturally occurring hydrophobic sediments might change in the presence of oil. Recent advances in materials physics have shown bio-inspired slippery liquid infused porous surfaces (SLIPS) and lubricant impregnated surfaces (LIS) can produce super slippery surfaces with excellent water shedding properties. Here we apply this new understanding to the physics of soil water repellency and address how the presence of oil, whether from contamination or otherwise, might influence water infiltration. We hypothesise that oil impregnating a hydrophobic soil may create stable oil coatings and/or layers that create soil surfaces resistant to water infiltration and with enhanced run-off of water. Using monolayers of sand, silt and clay particles treated with a commercial hydrophobising agent and silicone oil, we created model (oil-free) hydrophobic and oil impregnated hydrophobic soils. Static water contact angles and droplet sliding angles were used to classify their degree of hydrophobicity and ability to shed water. Our results show that in the absence of oil, model hydrophobic soil surfaces with particle sizes below 63μm are superhydrophobic with water droplet contact angles above 150 degrees. In the presence of oil, we observed a sediment-based SLIP/LI surface on particle sizes below 63μm with water contact angles of 90 degrees and droplet sliding angles of below 5 degrees. We also achieved reduced sliding angles compared to the oil-free surfaces, and a conformal layer of oil on all particle sizes. These results support our hypothesis that SLIPS/LIS may occur in natural soil systems. These results have implications for soil water repellency, oil clean up from soil and for processes occurring in other sedimentary environments caused by both naturally occurring and anthropogenic contamination of oils.

How to cite: McCerery, R., Woodward, J., McHale, G., and Winter, K.: Water Shedding Properties of Oil Impregnated Hydrophobic Soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-765, https://doi.org/10.5194/egusphere-egu2020-765, 2020.

Quantitative and Qualitative description of infiltration into soils in general and initially dry soils in particular those in which the hydraulic properties vary spatial and temporal have been challenging soil physicists and hydrologists. Water repellent soils, whose contact angle is higher than 40° and can even reach values that are greater than 90° (noted as hydrophobic soils) are an example of such challenge cases. Infiltration in these soils takes usually place along preferential flow pathways (noted as gravity-induced fingering), rather than in a laterally uniform moving wetting front. The water content and capillary pressure distributions along these fingers are non-monotonic with water accumulation behind the moving wetting front (noted as saturation overshoot) and a decreasing water content toward the soil surface. Being a parabolic-type partial differential equation, the Richards equation that is commonly used to model flow in soils can't handle such water content/pressure distributions. Many attempts have been made to modify the Richards equation to enable it to model the non-monotonic water content profiles. These attempts that are not based on the measurable soil properties that can highlight the physics that induces the formation of such non-monotonic distribution.  

A new conceptual modelling approach, noted as the moving-boundary approach, will be presented. This approach overcomes the existing theoretical gaps in the quantitative descriptions that have been suggested for the non-monotonic water content distribution in the gravity-induced fingers. The moving-boundary approach is based on the presumption that non-monotonicity in water content is formed by an intrinsic higher-than-zero contact angle. Note that non-zero contact angle have been rarely incorporated in models used for quantifying infiltration into field soils, in spite of the findings that most soils feature some degree of repellency. The verified moving-boundary solution will be used to demonstrate the synergistic effect of contact angle and incoming flux on the stability of 2D flow and its associated plume shapes. The physically-based moving-boundary approach fulfils several criteria raised by researchers to adequately describe gravity-driven unstable flow.

How to cite: Wallach, R. and Brindt, N.: Modelling gravity-driven fingering in soils having an intrinsic non-zero contact angle (water repellent soils) using the innovative moving-boundary approach , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2647, https://doi.org/10.5194/egusphere-egu2020-2647, 2020.

Trees in arid and semi-arid regions are faced with water shortages at most times, and the use of water storage in tree stem is an important mechanism and pathway for adaptation to drought. In this research, we have explored the tree saplings in semi-arid areas by continuous monitoring and analysis of the sap flux at stem top and stem breast, in the main growth season. A primary objective is to find out when and how trees use stem water storage as a reservoir, and more specifically if there is a difference in stem flow start time between stem top and stem breast. Our study shows that in sunny day of the growing season, the sap flow at stem top start time is later than the sap flow at stem breast, with the maximum of time lag about 60 mins, and the daily sap flow peak time of stem top is later than that of the stem breast by 1-2 hrs. The maximum daily flux at stem top is about 1.4-2.1 times greater than that at stem breast. Stem water storage increases the drought tolerance of trees. The depletion stage of stem water storage mainly occurs in early morning, and then enters the replenishing phase in the afternoon. In a sunny day, with the increase of soil water deficit with relative extractable water (REW) (or the relative effective soil water index) less than 0.43, demand for water storage of stem is more significant, and its role is mainly based on the depletion process. When the soil moisture condition is improved, the process is dominated by replenishing. From the results of continuous observations throughout the growing season, the depleting and replenishing processes can achieve equilibrium in a short period of time (like a few days). This research has advanced our understanding of the utilization mechanism of tree stem storage water in semi-arid areas.

How to cite: Cheng, Y., Wang, Y., and Jiang, Q.: A field study of depletion-replenish water storage mechanism in tree stems in semi-arid region , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14585, https://doi.org/10.5194/egusphere-egu2020-14585, 2020.

Testing new experimental procedures to assess the effects of the drops impact on the soil sealing formation is a main topic in soil hydrology.

In this field investigation, the methodological approach proposed first by Bagarello et al. (2014) was extended to account for a greater soil infiltration surface (i.e., about 3.5 times higher), a higher range and number of heights of water pouring and to evaluate the different impact on soil management. For this purpose, the effects of three water pouring heights (low, L=3 cm; medium, M=100 cm; high, H=200 cm) on both no-tilled (NT) and conventionally tilled (CT) loam soil were investigated by Beerkan infiltration runs and using the BEST-procedure of data analysis to estimate the soil hydraulic properties.

Final infiltration rate decreased when perturbing runs (i.e., M and H) were carried out as compared with the non-perturbing (L) ones (by a factor of 1.5-3.1 under NT and 3.4-4.4 under CT). Similarly, the water retention scale parameter, h_g, increased (i.e., higher in absolute terms) by a factor 1.6-1.8 under NT and by a factor 1.7 under CT. Saturated hydraulic conductivity, K_s, changed significantly as a function of the increase of water pouring height; regardless of the soil management, perturbing runs caused a reduction in soil permeability by a factor 5 or 6. Effects on hydraulic functions (i.e., soil water retention curve and hydraulic conductivity function), obtained with the BEST-Steady algorithm, were also highlighted. For instance, differences in water retention curve at fixed soil pressure head values (i.e., field capacity, FC, and permanent wilting point, PWP) due to perturbing and non-perturbing runs, were estimated as higher under NT (3.8%) than CT (3.4%) for FC, and equal to 2.1% or 1.6% for PWP.

Main results of this investigation confirm that a recently tilled loamy soil, without vegetation cover, can be less resilient as compared to a no-tilled one, and that tested water pouring heights methodology looks promising to mimic effects of high energy rainfall events and to quantify the soil sealing effects under alternative management of the soil.

Acknowledgments

The work was supported by the project “STRATEGA, Sperimentazione e TRAsferimento di TEcniche innovative di aGricoltura conservativA”, funded by Regione Puglia–Dipartimento Agricoltura, Sviluppo Rurale ed Ambientale, CUP: B36J14001230007.

 References

Bagarello, V., Castellini, M., Di Prima, S., Iovino, M. 2014. Soil hydraulic properties determined by infiltration experiments and different heights of water pouring. Geoderma, 213, 492–501. https://doi.org/10.1016/j.geoderma.2013.08.032

How to cite: Castellini, M., Di Prima, S., Stellacci, A. M., Iovino, M., and Bagarello, V.: Testing an infiltrometer methodology to investigate water impact effects on both soil sealing and hydraulic properties of a loam soil under conventional tillage and no-tillage, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22632, https://doi.org/10.5194/egusphere-egu2020-22632, 2020.

Recently, cities growth has enhanced economic development but also generates different problems that affect the population such as stormwater drainage. It is known that the area available for water infiltration decrease in these urban centers generating scenarios of high vulnerability and risk of flooding associated with extreme weather events of precipitation. Therefore, an alternative is the implementation of Sustainable Urban Drainage systems (SUDs) that allows high efficiency in the control and local infiltration of rainwater. SUDs are often built with technosoils from the recycling of materials from different industries, for which it is necessary to study their hydraulic and solute retention properties. Indeed, one of the functions of SUDs must therefore be the retention of pollutants before they reach the groundwater. Therefore, this research aimed to evaluate the retention capacity of metallic solutes Pb and Cu in technosoils (compacted mixture of sand, loam and rice husk ash) proposed for SUDs in Bogota, Colombia. A research work was conducted by combining adsorption isotherms measurements, unsaturated column breakthrough flow experiments and numerical modeling with RETC, STANMOD and HYDRUS 1D models. Adsorption isotherm can be described satisfactorily using the Freundlich and Langmuir models. Additionally, unsaturated soil column leaching tests (ISO/TS S1268-3) allows estimation of solute diffusion through the soil profile. A multi-reaction model (MRM) and convection dispersion flow model reveal non-linear and non-equilibrium in the movement of solute in soil. Moreover, there is a competition for adsorption of metal ions in the technosoil profile; the order of selectivity of heavy metals in the active sites of the microporal network will be Pb⁺²> Cu⁺², so that these technosoil is a favorable material in heavy metals retention.

How to cite: Sanchez Hernandez, K. A., Santos Granados, G. R., Angulo-Jaramillo, R., González Murillo, C. A., and Lozada Lopez, C.: Evaluation of the retention capacity of Pb and Cu in technosoils of Sustainable Urban Drainage Systems (SUDs) in Bogota, Colombia , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1056, https://doi.org/10.5194/egusphere-egu2020-1056, 2020.

The macroscopic capillary length is a critical parameter for the modeling of infiltration in single-ring experiments. Current methods to quantify this parameter either require multiple infiltration experiments, thus increasing effort and potential for error, or laboratory characterization that does not reflect field condition. We propose a simple field method for the estimation of the macroscopic capillary length, λ_c, from Beerkan runs (single-ring infiltration experiment with measurements of initial and saturated soil water contents). In the proposed method, we use the final portion of the cumulative infiltration, corresponding to the steady state of the water infiltration, to develop a reliable predictor of λ_c. The proposed model was validated using analytically generated data along with an experimental database that included 433 Beerkan runs from a wide range of conditions and types of soils. The analytical validation demonstrated the reliability of the proposed λ_c estimates for different soil textures and initial soil water contents. Altogether, the proposed method constitutes a simple solution for estimating λ_c, and it can improve our ability to estimate K_s in the field.

How to cite: Di Prima, S., Stewart, R. D., Castellini, M., Bagarello, V., Abou Najm, M. R., Pirastru, M., Giadrossich, F., Iovino, M., Angulo-Jaramillo, R., and Lassabatere, L.: Estimating the macroscopic capillary length using steady state infiltration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4097, https://doi.org/10.5194/egusphere-egu2020-4097, 2020.

Surfactants have been widely used in agriculture mainly as adjuvants to aid foliar pesticides to stay on target areas and as wetting agents to counteract the deleterious impacts of soil hydrophobicity. The latter has gained increasing attention among scientists over decades. Many natural and urban hydrophobic soil surfaces (i.e post-fire forest land and golf greens with dry patches respectively) after surfactant application has observed to have improved hydrological behaviors such as enhanced infiltration rate, more evenly-distributed water content, thus resulting in higher water use efficiency, better performances of amenity surfaces and higher crop yield. In general, a surfactant can be classified as cationic, anionic or nonionic according to the charge of its polar group. Commonly, with anionic and nonionic surfactants are employed by either directly mixing with the soil or incorporated into the irrigating. Regardless of the application mode, the occurrence of surfactant adsorption onto soil particles after wetting/drying cycles is highly expected, which, in fact, has already shown in some studies to change the hydraulic properties of the soil, oppositely to initial expectation. Capillary rise, for example, was found to decrease in sand treated with laundry derived detergent. In addition, sub-critical hydrophobicity was observed in sands pre-saturated with greywater derived surfactants after some cycles of wetting and drying. Insights from these studies implied that surfactant application to hydrophilic soils may eventually induce temporal hydrophobic nature. In this regard, the main objective of this study was to quantify the sorptivity and imbibition rate of air-dry soil subjected to wetting and drying with surfactants. Specifically, we employed three types of surfactants: (i) anionic (SDS), (ii) cationic (CTAB) and (iii) nonionic (TX-100). Quartz sand was sieved through 0.5mm sieve and wet-packed into columns (I.D.=3.5cm and L=6cm) with surfactant concentrations above and below the CMC (Critical Micelle Concentration) and then oven-dried at 65^oC for 24h. We have repeated this procedure to obtain soil samples undergoing 1 to 5 wetting/drying cycles. The soil samples were subjected to imbibition using the capillary rise method with water and ethanol, from which the initial sorptivity, imbibition rate and contact angle (CA) were calculated. The Wilhelmy plate method (WPM) and sessile drop method (SDM) was also used to measure the CA. The results showed that following one application of the three surfactants, the sorptivity was reduced relative to the control. Further reduction observed only for TX-100 and CTAB soil samples. The CA values obtained from the WPM and SDM implied that sub-critical hydrophobicity was induced only for the CTAB-treated, implying that water imbibition in the SDS and TX-100 treated soil in manly governed by the reduced surface tension rather than in the induced hydrophobicity (i.e. CA). Further discussion on the governing mechanism of wetting in surfactant-containing soils will be presented next to the results.           

How to cite: Nguyen, T. and Arye, G.: Sorptivity and water imbibition into air-dry surfactant-containing soil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5565, https://doi.org/10.5194/egusphere-egu2020-5565, 2020.

Soil sorptivity is one of the key hydraulic parameters for modelling water infiltration into soil. It quantifies the capacity of a soil to infiltrate water by capillarity. Several formulations, based on various models, have been proposed to compute it from the water retention and the unsaturated hydraulic conductivity functions. All these formulations use the integration of the product of either the hydraulic conductivity or diffusivity function with the flux concentration function. The integration can be performed either over an interval of water pressure head or water content, yielding two equal values. However, the expression of the integral as a function of water pressure head may involve a huge or even infinite interval, which can be numerically difficult to handle. In opposite, the expression of the integral as a function of water content involves the integration of a diverging function (diffusivity) over a large interval, which is also troublesome from a numerical point of view. In this paper, we provide a new expression for sorptivity by cutting the integral in two parts, in order to involve only the integration of a finite function over a finite interval. The dependency of the integral on the flux concentration function is also investigated.

How to cite: Peyneau, P.-E., Lassabatere, L., Pollacco, J., Fernández-Gálvez, J., Latorre, B., Moret-Fernández, D., Di Prima, S., and Angulo-Jaramillo, R.: Finite formulation for the computation of sorptivity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22664, https://doi.org/10.5194/egusphere-egu2020-22664, 2020.

Soil hydraulic characterization is crucial to describe the retention and transport of water in soil, but current methodologies limit its spatial applicability. This work presents a cost-effective general Beerkan Estimation of Soil Transfer parameters (BEST) methodology using single ring infiltration experiments to derive soil hydraulic parameters for any type of unimodal water retention and hydraulic conductivity functions. The proposed method relies on the BEST approach. The novelty lies in the use of Kosugi hydraulic parameters without need for textural information. Kosugi functions were chosen because they are based on physical principles (log-normal distribution for pore size distributions). A link between the Kosugi parameters (i.e., relationship between σ and h_kg) was introduced to reduce the number of parameters estimated and to avoid the need for information on the soil texture. This simplifies the procedures and avoids sources of errors related to the use of pedotransfer functions as for the previous BEST methods. Lastly, the method uses a quasi-exact formulation that is valid for all times, instead of the approximate expansions previously used, avoiding related inaccuracy and allowing the use of any infiltration data encompassing or not both transient and steady states. The new BEST methods were tested against numerically generated data for several contrasting synthetic soils, and the results show that these methods provide consistent hydraulic functions close to the target functions. The new BEST method is accurate and can use any type of water retention and hydraulic conductivity functions (Fernández-Gálvez et al., 2019).

Reference

Fernández-Gálvez, J., Pollacco, J.A.P., Lassabatere, L., Angulo-Jaramillo, R., Carrick, S., 2019. A general Beerkan Estimation of Soil Transfer parameters method predicting hydraulic parameters of any unimodal water retention and hydraulic conductivity curves: Application to the Kosugi soil hydraulic model without using particle size distribution data. Adv. Water Resour. 129, 118–130. https://doi.org/10.1016/j.advwatres.2019.05.005

How to cite: Fernández-Gálvez, J., Pollacco, J., Lassabatere, L., Angulo-Jaramillo, R., and Carrick, S.: A general BEST method predicting soil hydraulic parameters for any type of water retention and hydraulic conductivity curves, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7232, https://doi.org/10.5194/egusphere-egu2020-7232, 2020.

Nowadays soil erosion control using different amendments has grown up worldwide. However, the application of transformed materials like biochar has not been adequately studied. In the same vein, the application of biochars produced from waste materials that harm nature, and impose cost to managers and producers is a valuable approach for optimal utilization of the resources. Towards this, the performance of biochar produced from deleterious raw vinasse as the main by-product of sugarcane industries in controlling soil splash and interrill erosions on two marl and loess soils from Iran was investigated. The study was performed in 0.5 m×0.5 m plots in three replicates installed in the field with a slope steepness of 25% subjected to a simulated rainfall with an intensity of 50 mm h^-1 and 0.5 h duration. Analysis of the results obtained from the splash and interrill erosions during the rainfall-runoff process showed that biochar decreased soil loss compared to the control plot on Marl soil but to a small extent (p > 0.05). However, the plot treated with biochar on the loess soil revealed significant (p<0.05) reduction in soil loss in comparison with that of the control plot. That study clearly demonstrates the addition of biochar may promote stability and limit both runoff and soil erosion. However, such effects strongly depend on the type of soils.

How to cite: Sadeghi, S. H., Kiani-Harchegani, M., Hazbavi, Z., Younesi, H., Sadeghi, P. S., Angulo-Jaramillo, R., and Lassabatere, L.: How different are effects of vinasse biochar on soil erosion in Loess and Marl soils?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5080, https://doi.org/10.5194/egusphere-egu2020-5080, 2020.

With the recent progress in soil structure imaging it is now possible to assess the properties of soil samples using pore-scale modelling. In this contribution we focus on saturated hydraulic conductance which can be easily modelled by solving Stokes equation in 3D pore geometry with the help of FDMSS software (Gerke et al., 2018) or pore-networks (Miao et al., 2017). We chose three soil images as obtained using microtomography device which were sampled in Russian Federation (Karsanina et al., 2018). As these are the gray-scale images representing attenuation of X-rays within the studied sample, before performing any modelling we need to classify all gray-scale voxels into pores and solids. Current state-of-the arts methods are represented by local segmentation methods which has two thresholds: 100% pores and 100% solids, the voxels in between are assigned to either pores or solids based on some considerations such as neighbors or by growing pore/solid phases from these 100% areas until they fill the whole space. We utilized such local binarization converging active contours (CAC) method (Sheppard et al., 2004) to segment soil images with manually chosen thresholds. Next, the same images were segmented using convolutional neural network (CNN) with U-net architecture. We compared the simulated saturated hydraulic conductances for images obtained by two different binarization approaches to show that if CNN is trained based on CAC segmentations the resulting physical properties are close to that of the CAC itself. This means that if the true data for CNN segmentation would be available, the conundrum we believe can be solved using multi-scale structure modelling techniques (Gerke et al., 2015; Karsanina and Gerke, 2018), our flow simulations based on CNN binarization would be of high accuracy and would require no operator input. We discuss critical implications of machine learning based segmentations for soil images and what it means as related to pore-scale modelling.

This research was supported by Russian Science Foundation grant 19-74-10070.

References:

Karsanina, M. V., Gerke, K. M., Skvortsova, E. B., Ivanov, A. L., & Mallants, D. (2018). Enhancing image resolution of soils by stochastic multiscale image fusion. Geoderma, 314, 138-145.

Gerke, K. M., Karsanina, M. V., & Mallants, D. (2015). Universal stochastic multiscale image fusion: an example application for shale rock. Scientific reports, 5, 15880.

Gerke, K. M., Vasilyev, R. V., Khirevich, S., Collins, D., Karsanina, M. V., Sizonenko, T. O., Korost D.V., Lamontagne S., & Mallants, D. (2018). Finite-difference method Stokes solver (FDMSS) for 3D pore geometries: Software development, validation and case studies. Computers & Geosciences, 114, 41-58

Sheppard, A. P., Sok, R. M., & Averdunk, H. (2004). Techniques for image enhancement and segmentation of tomographic images of porous materials. Physica A: Statistical mechanics and its applications, 339(1-2), 145-151.

Karsanina, M. V., & Gerke, K. M. (2018). Hierarchical Optimization: Fast and Robust Multiscale Stochastic Reconstructions with Rescaled Correlation Functions. Physical Review Letters, 121(26), 265501.

Miao, X., Gerke, K. M., & Sizonenko, T. O. (2017). A new way to parameterize hydraulic conductances of pore elements: A step towards creating pore-networks without pore shape simplifications. Advances in Water Resources, 105, 162-172.

How to cite: Romanenko, K., Lavrukhin, E., Vasilyev, R., and Gerke, K.: Modelling soil physical properties based on XCT scans processed using state-of-the-art local and machine learning based segmentation approaches, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8946, https://doi.org/10.5194/egusphere-egu2020-8946, 2020.

In numerous applications the most critical step between studying soil structure with the help of X-ray tomography and its quantitative analysis is image segmentation; the simplest type is a division of the gray-scale images into solids and pores – or binarization, is necessary to perform pore-scale simulations (Gerke et al.,2018). This can be performed by either manual or automatic methods. Current state-of-the-art methods mainly include so called local segmentation where for each two phases one needs two confidence thresholds, i.e., 100% pores and 100% solids for binarization. These thresholds are either chosen manually (Karsanina et al.,2018) or automatically, the pixels/voxels in between these thresholds are classified according to some statistical measure or by growing phases from seeds. In case of global methods there is a single threshold that divides the histogram into pores and solids explicitly. There is, however, a class of popular automatic global/local methods based on gray-scale image variance minimization – Otsu’s method and its variations (Hapca et al.,2013), numerous related techniques are available in popular image processing software – ImageJ and SoilJ (Koestel,2018). The aims of our work to test Otsu-based techniques applicability to various soils and imaging resolutions.

In our study, we compared the results of using different variations of Otsu’s method working for 2D and fully 3D images for a number of soil samples of different sizes and taken at different resolutions: 240, 100, 16, 1µm. The largest samples - monoliths with a diameter of 10 cm were taken with the coarsest resolution, mesopores were segmented in micromonoliths with a diameter of 2 cm, with the most detailed resolution the pore space of microaggregates was investigated and segmented (fraction 2-1 mm). All objects of study have individual characteristics.

According to the results of the study, it can be argued that the Otsu method (3D) with a high degree of reliability worked only for detailed images of microaggregates. Its usage for all soils is generally unacceptable, as we observed for all other samples studied here. Moreover, automatic Otsu and related methods do not perform satisfactory on images with histograms resembling highly hierarchical structures (Gerke et al.,2015), which is true for all structured soils (Karsanina et al.,2018).

This research was supported by the RSF grant 19-74-10070.

References:

Karsanina, M.V., Gerke, K.M., Skvortsova, E.B., Ivanov, A.L., & Mallants,D.(2018). Enhancing image resolution of soils by stochastic multiscale image fusion. Geoderma,314, 138-145.

Gerke, K.M., Karsanina, M.V., & Mallants, D. (2015). Universal stochastic multiscale image fusion: an example application for shale rock. Scientific reports,5, 15880.

Hapca, S.M., Houston, A.N., Otten, W., & Baveye, P.C. (2013). New local thresholding method for soil images by minimizing grayscale intra-class variance. Vadose Zone Journal,12(3).

Gerke, K.M., Vasilyev, R.V., Khirevich, S., Collins, D., Karsanina, M.V., Sizonenko, T.O., Korost D.V., Lamontagne S., & Mallants, D.(2018). Finite-difference method Stokes solver (FDMSS) for 3D pore geometries: Software development, validation and case studies. Computers & Geosciences, 114, 41-58

Koestel, J.(2018). SoilJ: an ImageJ plugin for the semiautomatic processing of three-dimensional X-ray images of soils. Vadose Zone Journal,17(1).

How to cite: Abrosimov, K., Romanenko, K., and Gerke, K.: Binarization of soil X-ray tomography images: revisiting Otsu’s method, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10758, https://doi.org/10.5194/egusphere-egu2020-10758, 2020.

Abstract:  Seepage process can be extensively observed in rainfall infiltration, natural waterways, artificial hydraulic constructions and other interactive phenomena between water and soil. Recent investigations targeting the deep water circulation as well as shifts of basin patterns induced by massive projects urge the need to enhance the understanding of seepage characteristics under profound depth (high packing state) and great hydraulic pressure. Alluvial gravelly soil is an ordinary weathering product in mountainous area, either exposed to the ground or embedded as a layer. This research focuses on the hydraulic conductivity of such soil. A novel large-scale triaxial seepage apparatus was designed with the capability of replicating densely packed soil specimen and simulating severe hydraulic conditions. Influences of both the packing state and the hydraulic pressures were experimentally studied. It is revealed while most existing permeability models present the rational description that hydraulic conductivity decreases with higher packing state, these formulas for non-plastic soil overestimate the hydraulic conductivity of gravelly soil more than one order of magnitude. The dependence of hydraulic pressure displays the similar trend, as increasing hydraulic gradient diminishes the hydraulic conductivity. Coupled hydro-mechanical permeability models are therefore introduced based on test results. No observation of obvious seepage failure illustrates that high packing state resulting from mechanical loads are favorable to prevention of soil erosion and corresponding countermeasures.

How to cite: Chen, C., Mei, S., and Chen, S.: Hydro-mechanical Dependent Hydraulic Conductivity within Alluvial Gravelly Soil: An Experimental Study, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13011, https://doi.org/10.5194/egusphere-egu2020-13011, 2020.

Today, due to climate change, soil degradation processes related to extreme water supply situations (flood, inland water or drought) are occurring more and more frequently. Soil structure is one of the most important soil characteristics influencing many transport of materials (transport, storage of heat, gas, water and nutrients).Furthermore, it defines and ultimately determines the significant physical, chemical and biological processes involved and also the most important factor in agricultural crop production. Permanent water cover has a significant effect on soil structure, but the dynamics of disaggregation and the role of the soil factors influencing it is not yet fully understood. Our basic research aim is to investigate the effect of permanent water cover on soil structure on representative Hungarian soil samples. In our experiment, we sought to find the answer to the question of how long-term water coverage causes changes and damage to the soil structure under laboratory conditions by artificial water cover. We measured aggregate stability with Mastersizer 3000 Hydro LV laser diffractometry device and some soil chemistry parameters with Agilent 4210 MP-AES at different water cover times (selected in the literature). Based on experiences the effect of persistent water cover from the soil structure side can be most noticeable in the changes of macro- and microaggregate stability, as well as in the change of certain chemical parameters (e.g. calcium and iron content), thus, the aim of our research was to investigate these characteristics also. After compiling our results in a database, we evaluated and deduced statistical data on the long-term degradation effects of water cover. We also made an attempt to describe its disaggregation dynamics for different Hungarian soil types. Based on the results, we have selected the most sensitive soils for permanent water cover, which are also expected to be sensitive to extreme water management related to climate change.

How to cite: Labancz, V., Sebők, A., Czinkota, I., Szegi, T., and Makó, A.: Effect of persistent water cover on soil structure, investigated on representative Hungarian soil samples, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19495, https://doi.org/10.5194/egusphere-egu2020-19495, 2020.

The Global Exploration Roadmap targets the realization of Mars manned exploration by the 2030s. It is necessary to understand water movement in porous media under microgravity to establish a plant growth system for crop production for astronauts to produce food in outer space. In previous researches, a decrease in infiltration rate was reported for coarse (1.5 mm diameter) glass beads porous media. On the other hand,  in the case of fine (0.4 mm diameter) glass beads porous media, the amount of reduction in the infiltration rate was small. We wanted knowledge of water movement under partial gravity conditions. We conducted water infiltration experiments under microgravity, 1/6G, and 1/3G conditions made by parabolic flights. The 0.2, 0.4, and 0.6 mm glass beads were used as porous media. The effects of particle size and partial gravity on water infiltration in porous media will be discussed.

How to cite: Sato, N., Maruo, Y., Nogawa, K., Naganuma, N., and Noborio, K.: Infiltration rate in unsaturated glass beads porous media under various gravity made by parabolic flight., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20786, https://doi.org/10.5194/egusphere-egu2020-20786, 2020.

In 2018 the weather in Germany was extreme: The highest temperatures since 1881 (= start of regular weather recording) were observed during the months of April – August (temperature anomaly of +3.6 K) and the second lowest precipitation amounts (anomaly of -150 mm). In that year, we measured the soil conditions (soil water tension, water content, electrical resistivity, temperature, seepage water at suction plates) in a maize field in Northern Germany continuously down to a depth of about 1.5 m using a combined geophysical and soil scientific small-scale instrumentation array.

This unique dataset revealed the heterogeneity of the subsurface water content, changes in soil water conductivity, heterogeneity of the water retention function, indications for preferential flow after the onset of precipitation (and locally increased nitrate concentrations) in seepage water. The electrical resistivity (ERT) data clearly detected the infiltration of local rainfall events by the change of near surface resistivity. The resistivity changes differ spatially reflecting dm-scale variations most probably caused by the dense maize plants. Soil water contents measured by TDR detected the summer rainfall events in some locations, in others, very small-scale preferential flow paths were found overlooked by ERT. The detected changes in pore water conductivity need to be taken into account when recalculating water contents from ERT data. Our data allow for a description of different scale effects on the derivation of flux processes and total flux estimations under extreme weather conditions but also show that cross-scale methods are needed for an adequate assessment of unsaturated flow.

How to cite: Susanne, S., Olga, F., and Ursula, N.: Heterogeneity of unsaturated flow measured in the dry summer of 2018 in Germany recorded by the combination of ERT and soil data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16417, https://doi.org/10.5194/egusphere-egu2020-16417, 2020.

 Human’s sphere of activities is going to expand to Moon and Mars on 2030s. As manned space mission getting longer, the importance of extra-terrestrial agricultural production increase not only for food production, but also for phycological benefit for astronauts. Water movement in porous media must be understood for secured plant growth, previous researches, however, reported that slower capillary flow was observed under microgravity than under Earth gravity (1 G). Air entrapment on pore neck may induce higher tortuosity and made capillary flow slower under microgravity. It was also reported that widening shape on capillary tube restrict water movement in capillary tube under microgravity. The diameter of capillary tube was relatively large (0.8 mm to 2.3 mm in-diameter) in the previous report; therefore, it is unclear that the result is applicable to the smaller pore structure like porous media. The objective of this study is (1) to evaluate capillary flow rate on convex and concave surface on the particle of porous media under microgravity and under 1 G, (2) to evaluate the water movement on widening area made by boundary between 0.8 mm and 1.0 mm glass beads. To make water movement visible, acrylic column of 2 mm thickness was chosen and was filled with 4 cm layer of 0.8 mm diameter glass beads and 3 cm layer of 1.0 mm diameter glass beads. Distilled water dyed with methylene blue solution was infiltrated into the glass beads under 2.4 s microgravity condition induced by 50 m free fall or under 1 G condition. Capillary flow was taken by high speed (960 fps) and closeup camera (DSC-RX100M5A, SONY) and split into image sequences to analyze with software (ImageJ). Both under microgravity and under 1 G, capillary flow stuck on the convex surface and hardly infiltrated into the concave surface, however, once water crossed over the convex surfaces, water moved on concave surfaces very fast. Pore was filled with water and air entrapment on pore neck, predicted on previous research, was not observed. The water front firstly reached on the boundary of 0.8 mm to 1.0 mm glass beads stopped, however, after the surrounding water front catch up, water crossed over the boundary. This result suggested that widening area restricted capillary flow, however it did not shut-off.

How to cite: Maruo, Y., Sato, N., Naganuma, N., Nogawa, K., Tsukano, M., Mizutani, H., and Noborio, K.: Millimeter scale water movement on convex and concave surfaces of porous media under microgravity., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16423, https://doi.org/10.5194/egusphere-egu2020-16423, 2020.

The continuous rain simulator used with very precise dosing enables both simulation of characteristic rainfall as well as accurate determination of infiltration rate and automatic calculation of hydraulic conductivity of soils under natural conditions. As a part of the research of infiltration processes induced by characteristic rainfalls, the effects of stormy rainfalls were verified in the described project stage. Stormy rain with constant intensity was applied by rain simulator in a single ring infiltrometer. Samples were tested in the laboratory (soils and kaolinite) and directly in the field. During rain infiltration was measured ponding time. Theoretical base of the research comes from non-steady state unsuturated vertical infiltration, which process (in one-dimensional flow conditions) can be described by Richard´s equation. Final simplified solution is provided by Philip´s simplified infiltration equtions. Hydraulic conductivity K was approximated from the analysis of time series of the process of vertical non-steady cumulative infiltration, going after ponding time. Sorptivity S was calculated by the numerical experiment with known values of stormy rain intensity, ponding time and hydraulic conductivity. Compared to traditional methods (single or double ring infiltrometer), soil hydro-physical characteristic (K, S) determined by this method is more reliable, informative and verified by ponding time.

How to cite: Pelíšek, I., Štibinger, J., Kulhavý, Z., and Melorio, L.: Ponding time, hydraulic conductivity and sorptivity – experimental determination by a single ring infiltrometer with rain simulator, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21431, https://doi.org/10.5194/egusphere-egu2020-21431, 2020.