HS8.1.6

EDI

This session deals with the use of geophysical methods for the characterization of subsurface properties, states, and processes in contexts such as hydrology, agriculture, contaminant transport, etc. Geophysical methods potentially provide subsurface data with an unprecedented high spatial and temporal resolution in a non-invasive manner. However, the interpretation of these measurements is far from straightforward in many contexts and various challenges remain. Among these are the need for improved quantitative use of geophysical measurements in model conceptualization and parameterization, and the need to move quantitative hydrogeophysical investigations beyond the laboratory and field scale towards the catchment scale. Therefore, we welcome submissions addressing advances in the acquisition, processing, analysis and interpretation of data obtained from geophysical and other minimally invasive methods applied to a (contaminant) hydrological context. In particular, we encourage contributions on innovations in experimental and numerical methods in support of model-data fusion, including new concepts for coupled and joint inversion, and improving our petrophysical understanding on the link between hydrological and geophysical properties.

Convener: Damien Jougnot | Co-conveners: Ellen Van De VijverECSECS, Ulrike Werban, Philippe Leroy, Remi Clement
Presentations
| Tue, 24 May, 10:20–11:50 (CEST)
 
Room 2.17

Presentations: Tue, 24 May | Room 2.17

10:20–10:22
10:22–10:32
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EGU22-13059
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solicited
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Presentation form not yet defined
Jan Vinogradov, Miftah Hidayat, Yogendra Kumar, David Healy, and Jean-Christophe Comte

Previous field self-potential (SP) surveys have suggested this passive, non-intrusive geophysical method to be a powerful tool for characterizing subsurface flow of water in shallow fractured systems. However, to accurately interpret the measured signal requires knowledge of electrochemical properties of these settings. Despite the interest, the controls on the electric surface charge and the zeta potential of gneiss at conditions relevant to naturally fractured systems remain unreported. There are no published zeta potential measurements conducted in such systems at equilibrium, hence, the effects of composition, concentration and pressure remain unknown. This study reports zeta potential values measured in a fractured gneiss sample, obtained from the Lewisian complex in NW Scotland, and saturated with NaCl solutions of various concentrations, artificial seawater and artificial groundwater solutions under equilibrium conditions at confining pressures of 4 MPa and 7 MPa. The constituent minerals of the sample were identified using X-ray diffraction and linked to the concentration and composition dependence of the zeta potential. The results reported in this study demonstrate that the zeta potential of gneiss was unique and dissimilar to pure minerals such as quartz, calcite, mica or feldspar. Moreover, the measured zeta potentials suggest that divalent ions (Ca2+, Mg2+ and SO42−) acted as potential determining ions. The zeta potential was also found to be independent of salinity in the NaCl experiments, which is unusual for most reported data. Moreover, the impact of fracture aperture on the electrokinetic response was investigated and likely implications for characterization of fractured systems using SP analyzed. Our novel results are an essential first step for interpreting field SP signals and facilitate a way forward for characterization of water flow through fractured basement aquifers.

How to cite: Vinogradov, J., Hidayat, M., Kumar, Y., Healy, D., and Comte, J.-C.: Zeta Potential of Fractured Gneiss Saturated with NaCl and Natural Aqueous Solutions – Impact of Composition, Concentration and Fracture Aperture on SP Signal in Response to Water Flow in Fractured Crystalline Bedrock, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13059, https://doi.org/10.5194/egusphere-egu22-13059, 2022.

10:32–10:37
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EGU22-2636
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Presentation form not yet defined
Philippe Leroy, Shuai Li, Alexis Maineult, and Jan Vinogradov

The zeta potential is a measureable electrical potential of paramount importance to understand the electrochemical properties of colloids and grains in contact with brines. However, the zeta potential remains poorly understood because it takes place at the nanoscale of the electrical double layer on the mineral surface. Streaming potential measurements on quartz-rich Fontainebleau and Lochaline sandstones carried out at high salinity (above 0.1 M NaCl) yield surprisingly high zeta potential values. We found that placing the shear plane, where the zeta potential is defined, slightly closer to the mineral surface than the outer Helmholtz plane significantly improves the predictions of the zeta potential and surface charge density of quartz at high salinity as well as the values of the equilibrium constant describing sodium adsorption in the Stern layer. Our results have strong implications for the modelling of the electrochemical properties of minerals in contact with highly saline solutions.

How to cite: Leroy, P., Li, S., Maineult, A., and Vinogradov, J.: The zeta potential of quartz. Surface complexation modelling to elucidate high salinity measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2636, https://doi.org/10.5194/egusphere-egu22-2636, 2022.

10:37–10:42
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EGU22-11720
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Virtual presentation
Damien Jougnot, Bertille Loiseau, Simon Carrière, Cédric Champollion, Emily Voytek, and Nolwenn Lesparre

Characterizing and monitoring water flow in the critical zone is of uttermost importance to understand the water cycle. Water link several process within critical zone from aquifer recharge and solute transfer to eco-hydrology, many eco-systemic services and biogeochemical reactions. However, the in situ quantification of water flow is technically challenging using traditional hydrological methods and numerous gaps of knowledge remain. The self-potential (SP) method is a passive geophysical method that relies on the measurement of naturally occurring electrical field. One of the contributions to the SP signal is the streaming potential, which is of particular interest in hydrogeophysics as it is directly related to both the water flow and porous medium properties. Unlike tensiometers and other point sensors, which use the measurement of state (e.g., matric pressure) at different locations to infer the intervening processes, the SP method measures signals generated by dynamic processes (e.g. water movement). However, the amplitude of the SP signal depends on multiple soil properties which are dependent to soil type, moisture content, and water chemistry (composition and pH). During the last decades, many models have been proposed to relate the SP signal to the water flow. In this contribution, we will present a soil-specific petrophysical model to describe the electrokinetic coupling generated from different water fluxes in the critical zone: rain water infiltration and water uptake from tree-roots. We tested a fully coupled hydrogeophysical approach on a large SP dataset collected in a two-dimensional array at the base of a Douglas-fir tree (Psuedotsuga menziesii) in the H.J. Andrews Experimental Forest in central Oregon, USA. We collected SP measurements over five months to provide insight on the propagation of transpiration signals into the subsurface with depth and under variable soil moisture. The coupled model, which included a root-water uptake term linked to measured sap flux, reproduced both the long-term and diel variations in SP measurements, thus confirming that SP has potential to provide spatially and temporally dense measurements of transpiration-induced changes in water flow. Similar set-ups are being installed on several test-sites of the French Critical Zone observatory network, OZCAR: Larzac, LSBB, Strengbach. This will allow us to test the approach under different climatic conditions, different soil types and in different ecohydrological systems.

How to cite: Jougnot, D., Loiseau, B., Carrière, S., Champollion, C., Voytek, E., and Lesparre, N.: In situ monitoring of rain infiltration and evapotranspiration in the critical zone using self-potentials, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11720, https://doi.org/10.5194/egusphere-egu22-11720, 2022.

10:42–10:47
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EGU22-5638
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ECS
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Presentation form not yet defined
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Veronika Iván, Benjamin Mary, Nimrod Schwartz, Massimiliano Ghinassi, and Giorgio Cassiani

Geoelectrical methods provide diverse toolsets to image the subsurface and monitor its water dynamics. These observations might be crucial in arid areas, where the structure and function of agricultural and natural ecosystems are dramatically determined by water availability. Dryland ecosystems can be characterized by heterogeneous soil cover, high salt content in upper soil layers and low levels of soil moisture. However, understanding the combined effect of soil water content, salinity and soil composition on the electrical signal remains a challenging issue. Recent studies demonstrated the sensitivity of the IP method to water content [1; 2], clay content [3] and salinity [4; 5]. [4] noted that the quadrature conductivity is weakly dependent on the pore fluid salinity, thus, it might be used to separate between pore water salinity and water content.

Here, in a laboratory experiment series, we conducted spectral measurements on artificial soils in small sample holders to observe under controlled conditions how the IP response is affected by water saturation and salinity. This laboratory setup with manipulated gradients of water content and salinity levels allowed to perform measurements with high accuracy, and establish relationships between the electrical and hydrological properties of unconsolidated deposits or soils. Sand-clay mixtures were used, consisting of very fine-coarse sand and clay powder (Ca-montmorillonite) which were mixed during multiple dry-wet mixing cycles with gradually growing clay content (0-8 %). The samples were packed under dry conditions and afterward saturated with tap water. The decreasing water content was obtained by air injection with growing pressure (0,05-2,5 bar). At the second phase of the experiment, the salinity was increased through the pore water (NaCl solution up to the electrical conductivity of 7000 μS/cm). Regression analysis is carried out on the obtained dataset to calibrate the sensitivity of the complex resistivity to the changing parameters at different frequencies. Based on the preliminary results, the method may have the potential for the construction of a pedophysical model, allowing the field application for water content monitoring in arid areas.

[1] Breede, K. et al. (2012) ‘Spectral induced polarization measurements on variably saturated sand-clay mixtures’, Near Surface Geophysics, 10(6), pp. 479–489.

[2] Kremer, T. et al. (2016) ‘Modelling the spectral induced polarization response of water-saturated sands in the intermediate frequency range (10 2 –10 5 Hz) using mechanistic and empirical approaches’, Geophysical Journal International, 207(2), pp. 1303–1312.

[3] Osterman, G. et al. (2019) ‘Effect of clay content and distribution on hydraulic and geophysical properties of synthetic sand-clay mixtures’, GEOPHYSICS, 84(4), pp. E239–E253.

[4] Grunat, D.A. (2013) Effects of soil saturation and pore fluid salinity on complex conductivity. PhD Thesis. Rutgers University-Graduate School-Newark.

[5] Mendieta, A. et al. (2021) ‘Spectral Induced Polarization Characterization of Non‐Consolidated Clays for Varying Salinities—An Experimental Study’, Journal of Geophysical Research: Solid Earth, 126(4).

How to cite: Iván, V., Mary, B., Schwartz, N., Ghinassi, M., and Cassiani, G.: Spectral Induced Polarization: Laboratory measurements on artificial soils with varying water saturation, salinity and clay content, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5638, https://doi.org/10.5194/egusphere-egu22-5638, 2022.

10:47–10:52
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EGU22-4469
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ECS
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Virtual presentation
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Agnese Innocenti, Veronica Pazzi, Marco Napoli, Riccardo Fanti, and Simone Orlandini

The issue of salinity in agricultural soils is a growing problem. Soil with a high sodium content in the root growth zone compromises plant health and growth. Irrigation is one of the main techniques used to reclaim high-salt soils, as water dilutes the sodium concentration. In this study, electrical resistivity tomography (ERT) is proposed as a reliable non-invasive technique to quantify sault movement during the irrigation process. The first step was to identify the best set up of electrodes for this type of investigation. 3D-ERT measurements were carried out in two different campaigns to identify the most suitable electrode distribution. The study area is a segment of land, located in Barbaruta (GR, Italy) and used for the cultivation of melons. The investigation site is characterised by irrigated soils in which an accumulation of sodium has occurred over time. To detect the movement of salt during the irrigation phases, ERT surveys were carried out before, during, and after the irrigation phases.

Considering the objective of the experiment, the measurement carried out during the first campaign (July 2021) was performed by creating a 3D grid in which the 72 electrodes were spaced 0.2 m apart and arranged in 5 parallel lines, spaced 0.2 m apart, two of which (lines 1 and 5) were 2.8 m long, for a total of 15 electrodes, and three of which (lines 2, 3 and 4) were 2.6 m long, for a total of 14 electrodes. This configuration made it possible to include two melon plants.

The survey carried out in the second campaign (August 2021) was carried out with a 3D grid in which the 72 electrodes were spaced 0.3 m apart and arranged in three parallel lines, 0.3 m apart and 6.9 m long, for a total of 24 electrodes in each line. This configuration allowed five melon plants to be incorporated. A Dipole-Dipole configuration was adopted for all the acquisition of electrical resistivity data. The commercial software ViewLab 3D was used to process the geoelectric data.

Data analysis showed that the range of conductivity values increases from dry to wet soil conditions, and conductivity increases with depth. The ERTs sections, carried out after the irrigation phase, showed areas where conductivity decreases over time during irrigation, this can be explained by the leaching of salts because of water input. While other areas show higher conductivity after irrigation, and this may mean not only an increase in water content but also a displacement of salts with water input. For this reason, further analysis is required, including the use of Induced Polarisation (IP).

The test showed that the best configuration is the one with the electrodes arranged in three lines, as it allows more plants to be incorporated.

The test also led to the need to avoid stressing the plants during the measurement phase. This made it necessary to create a special set of electrodes to be installed during the transplanting phase, so as not to disturb the plants during the growth phas.

How to cite: Innocenti, A., Pazzi, V., Napoli, M., Fanti, R., and Orlandini, S.: Application of Electrical Resistivity Tomography (ERT) to study to soil water and salt movement under drip irrigation in a saline soil cultivated with melon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4469, https://doi.org/10.5194/egusphere-egu22-4469, 2022.

10:52–10:57
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EGU22-8137
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ECS
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Presentation form not yet defined
Monitoring of Agricultural Hydrodynamics and Investigation of Geophysical Relationships in African Alfisols using Electrical Resistivity Tomography
(withdrawn)
Russell Swift, Jonathan Chambers, Jimmy Boyd, Tongai Mtangadura, Elijah Phiri, Innocent Sandram, Phil Meldrum, Harry Harrison, Joseph Chimungu, Arnaud Watlet, Paul Wilkinson, Frédéric Nguyen, and Murray Lark and the CEPHaS Near-Surface Geophysics Team
10:57–11:02
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EGU22-10364
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Presentation form not yet defined
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Susann Birnstengel, Thomas Günther, Marco Pohle, Götz Hornbruch, Johannes Nordbeck, Uta Ködel, Ulrike Werban, and Peter Dietrich

Heat storage in aquifer structures takes on greater significance and is therefore an important subject for risk assessment and impact analysis on groundwater resources. Geophysical methods contribute substantially to the observation of hydrogeological processes by providing information
about physical subsurface properties. In order to allow for correct process interpretation, it is essential to find and evaluate their relationship
to the corresponding rock-physical parameters. Therefore a heat injection experiment and a corresponding monitoring system have been developed
and established in a shallow aquifer environment characterized by quaternary glaciofluvial sediments. The focus is on the investigation of coherence between geophysical proxies and the temperature distribution in the near-surface. A geological subsurface model derived from geophysical and hydrological pre-investigations has been used to simulate heat distribution and resulting electrical conductivity variations in the affected area.
Tests for thermal energy storage and extraction have been conducted via Aquifer thermal energy storage (ATES) system. With time-lapse inversion
we want to detect the direct impact of changing temperature distribution in the subsurface on the related electrical resistivity when heating the
aquifer up to 80 °C. Rein et al. (2004) state that electrical conductivity of the subsurface depends to a great extent on water saturation. Heating
up the governed pore water by 1 °C results in a linear relative electrical conductivity increase of 2.5% (Dachnov, 1962). Different inhole and cross-
hole arrays at the test site assure good coverage of the heated area and pass through the monitoring routine once a day. The ongoing injection
cycles consist of a heating period of 2 weeks, a down time of 3 weeks, an extraction period of 2 weeks and another down-time of 1 week followed by
the next cycle. We prove the applicability of heat injection and extraction monitoring by combined crosshole ERT (and seismic) and correlated
the resistivity with the directly measured temperature data of the temperature sensors additionally installed in the boreholes. At the highest
observed temperature level of 75 °C the electrical conductivity increases by a factor of three. 3D inversion allows for a direct reference to the temperature distribution in the subsurface. This study provides information about the resolution capacity of crosshole ERT for heat storage systems
in shallow aquifers.
These activities have been done within the follow-on TestUM-Aquifer Project - TestUM-II ”Cyclic high temperature - Aquifer thermal energy storage (ATES) experiment” funded by the BMBF (grant 03G0898A/B).

How to cite: Birnstengel, S., Günther, T., Pohle, M., Hornbruch, G., Nordbeck, J., Ködel, U., Werban, U., and Dietrich, P.: Monitoring of an aquifer thermal storage system in the field scale using crosshole ERT, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10364, https://doi.org/10.5194/egusphere-egu22-10364, 2022.

11:02–11:07
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EGU22-6956
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Presentation form not yet defined
Giorgio Cassiani, Matteo Censini, Paolo Nasta, Carolina Allocca, Benedetto Sica, Ugo Lazzaro, Caterina Mazzitelli, Matteo Verdone, Andrea Dani, Francesca Manca di Villahermosa, Daniele Penna, and Nunzio Romano

Hydrological processes along mountain hillslopes involve complex interaction between soil storage and surface and subsurface flow, drainage and evapotranspiration. To capture this complexity, time-lapse extensive and intensive measurements are needed, potentially capable of providing spatially dense information in 3D and time frequent data. To this end, hydro-geophysical methods (ground penetration radar, GPR, electromagnetic induction, EMI and electrical resistivity tomography, ERT) based on electrical and electromagnetic laws are widely used as they naturally link to the electrical properties of soil moisture. ERT produces, especially in time lapse mode and using permanent installations, very detailed images of the water dynamics along hillslopes. While ERT requires galvanic contact with the ground, and thus relatively slow operations, EMI can be applied over large areas in a very short time. This method has been used for decades, mainly to produce apparent electrical conductivity (ECa) maps. Only recently, inversion of EMI data as a function of depth has become a viable practice.

In this work, we present two cases of hillslope monitoring using non-invasive methods, both performed as part of the WATZON project, funded by the Italian Ministry of University and Research (MIUR). The first case is the Mediterranean catchment of the Alento River, in southern Italy. The monitoring was carried out using 7 different EMI surveys, acquired in multifrequency mode (FDEM) between August 2020 and December 2021. The purpose of this survey was to characterize the structure of the basin’s subsoil within the first few meters, as well as to record the variation of electrical conductivity (EC) associated with seasonal variations. The second case is related to the Apennines catchment of the Re Della Pietra, located at the border between Tuscany and Emilia-Romagna in central Italy. The monitoring was carried out through 6 different EMI surveys, acquired in multifrequency mode (FDEM) between August 2020 and May 2021. The purpose of this survey was to characterize the structure of the basin’s subsoil within the first few meters, as well as to record the variation of electrical conductivity (EC) associated with seasonal variations. Furthermore, ERT measurements were carried out along a fixed line on the ground, according to the direction of the maximum slope. The combination of EMI and ERT proved particularly effective in delineating the hydrologic dynamics of the hillslope.

How to cite: Cassiani, G., Censini, M., Nasta, P., Allocca, C., Sica, B., Lazzaro, U., Mazzitelli, C., Verdone, M., Dani, A., Manca di Villahermosa, F., Penna, D., and Romano, N.: Time-lapse multi-frequency EMI mapping and ERT profiling for the characterization of soil water behavior in mountain catchments. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6956, https://doi.org/10.5194/egusphere-egu22-6956, 2022.

11:07–11:12
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EGU22-1234
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ECS
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On-site presentation
Moustapha BA Mouhamadoul

The hyporheic zone is a thin porous sedimentary interface that connects the river to the water table. It is a place where a large part of the groundwater transits and mixes with surface water. Recent studies point to the key role of this zone, a natural biological reactor at the groundwater-river interface, in altering the nitrogen and carbon cycles, capturing and releasing contaminants and buffering river temperatures. Past studies have suggested that, locally hyporheic fluxes can overtake groundwater-river exchanges, although the physical conditions (permeability, roughness, head, ...) under which such scenario occurs remains unclear. In this study, geophysical monitoring of electromagnetic conductivity along a river reach (Sélune, France) was used to identify longitudinal variations in bed permeability, and identify potential hotspot of hyporheic exchanges.
In practice, we will measure electrical conductivity at different depths into the river sediment using the electromagnetic instrument “CMD explorer”. The instrument is displaced over the river surface using a floating board. A two-layer model is then considered to separate the contribution of sediment bed and water column conductivities. Based on the law (Archie, 1942) in a saturated environment, we link measured variations in electrical conductivity to variations in sediment properties such as pore volume change. In parallel, manual permeability measurements of the riverbed were performed to compare and validate the permeability deduced by the electromagnetic method.
The recent removal of two dams over the Sélune river which was associated with an abrupt change of transported sediment load motivates us to perform time-lapse measurements of electromagnetic conductivity in several sectors upstream and downstream of the dams, before and after removal. Such repeated measure provides interesting data on the time scales of bed clogging processes and its impact on hyporheic exchanges.

How to cite: Mouhamadoul, M. B.: Use of electromagnetic tools to evaluate the risk of silting of the ‘Sélune’ river bed following the dismantling of the 'Vezins' and 'Roche Qui Boit' dams., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1234, https://doi.org/10.5194/egusphere-egu22-1234, 2022.

11:12–11:17
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EGU22-5419
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On-site presentation
Mohammad Farzamian, Tiago B. Ramos, Ana R. Oliveira, Hanaa Darouich, Nadia Castanheira, Ana Marta Paz, and Maria Gonçalves

Irrigated agriculture plays a crucial role in the food supply in many countries where ecological conditions are characterized by warm and dry summers with high solar radiation and evapotranspiration rates. Evaluating spatio-temporal variability of soil water is critical for the delignating of management zones and optimal irrigation scheduling. However, the soil water content variability is normally obtained using simple water balance models and for representative areas, not taking into consideration the variability of soil properties. This is because for large-scale studies, the traditional sampling method is extremely difficult to implement and it remains critical to finding alternative methods of characterization of soil texture, which is required for soil hydraulic parameters assessment.

Geophysical techniques such as electromagnetic induction (EMI) provide enormous advantages compared to soil sampling because they allow for in-depth and non-invasive analysis, covering large areas in less time and at a lower cost. we carried out EMI surveys in a 23ha almond field, located in Alentejo, Portugal to evaluate the potential use of this methodology in mapping spatial distribution of soil texture in this water-scarce region. We firstly inverted field apparent conductivity data (σa) using a Quasi-3D inversion algorithm in order to obtain 3D electromagnetic conductivity images (EMCI) of the real soil electrical conductivity (σ) with depth. Afterward, we evaluated the possibility of establishing a linear regression (LR) relationship between σ and soil texture collected from 13 soil sample locations to a depth of 0.60 m. We concluded that it is possible to establish a relatively good LR between σ and clay and sand, allowing us to convert EMCI to clay and sand content maps and generate these maps for different depts. With this information at hand, pedotransfer functions were applied to define the soil hydraulic parameters necessary to run the distributed model and map the within soil variability at the field scale.

we used the MOHID-Land distributed process-based model to compute the variability of the soil water balance components in this field, at a resolution of 5m. Irrigation data was monitored on-site, at two locations, while weather data was extracted from a local meteorological station. The distributed modeling approach included the definition of potential evapotranspiration fluxes computed from the product of the reference evapotranspiration obtained according to the FAO56 Penman-Monteith equation and a crop coefficient for each stage of almond’s growing season, the variable-saturated flow using the Richards equation, and root zone water stress following a macroscopic approach. Modeling results are then used to present the maps of the variability of the seasonal actual crop transpiration and soil evaporation, the mean soil moisture, seasonal runoff, and seasonal percolation, which are then used to propose management zones for improving irrigation water use in the studied almond field.

Acknowledgments

This work was developed in the scope of SOIL4EVER “Sustainable use of soil and water for improving crops productivity in irrigated areas” project supported by FCT, grant no. PTDC/ASP-SOL/28796/2017.

 

 

 

 

How to cite: Farzamian, M., Ramos, T. B., Oliveira, A. R., Darouich, H., Castanheira, N., Paz, A. M., and Gonçalves, M.: Application of Electromagnetic Induction Method and Distributed Process-Based Modeling for Optimized Soil Water Variability Assessment , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5419, https://doi.org/10.5194/egusphere-egu22-5419, 2022.

11:17–11:22
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EGU22-5861
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ECS
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On-site presentation
Mirko Pavoni, Jacopo Boaga, Florian Wagner, Alexander Bast, and Marcia Phillips

The monitoring of alpine rock glaciers has both scientific and economic relevance. The degradation of mountain permafrost is a relevant proxy of climate change and global warming, but also a possible source of hazards for mountain communities since it can trigger natural processes such as rockfalls, debris flows, and floods. Geophysical techniques have been used to study these periglacial forms, particularly electrical and seismic refraction methods. Nevertheless, the independent data processing applied to these measurements does not lead to quantitative estimation of the physical components (air, water, ice, and rock) in the frozen subsoil. Moreover, the structural interpretation of the ground with independent resistivity and seismic sections can introduce ambiguities. To quantify the composition of the mountain permafrost, Wagner et al. (2019) developed a petrophysical joint inversion approach of electrical resistivity and seismic refraction datasets. We applied this method to several datasets collected in the rock glaciers of Schafberg (Engadin, Switzerland) and Ritigraben (Canton of Valais, Switzerland). To estimate the parameters in Archie’s and Timur’s laws, we performed the petrophysical joint inversion with a range of plausible values, selecting the ones that guaranteed the lowest final root-mean-square (RMS) error between the model response and the observed data. Our approach can be applied wherever information from boreholes is unavailable. This is a common situation in rock glacier studies since drilling in high mountain environments is very complicated and expensive. Finally, to improve the quality of individual resistivity and seismic velocity sections, we applied the structurally-coupled cooperative joint inversion method to our datasets, developed by Günther and Rücker (2008). This approach is based on the exchange of structural information between the independent geophysical inversions of electrical and seismic datasets. The process is driven by 3 different coupling parameters and the choice of their values has been done again by running the inversion with a range of values, choosing those that guaranteed the lowest final RMS. This method can be useful to better define the active layer thickness and the lower boundary of frozen ground. From the obtained results, it is clear that combined use of petrophysically-coupled and structurally-coupled joint inversion can represent a significant improvement for the characterization of mountain permafrost, in comparison to the traditional independent geophysical inversions, even in the absence of prior information from boreholes. In future studies, both structural and petrophysical coupling could be incorporated into a single inversion framework to adaptively allow structural agreement if quantitative petrophysical agreement cannot be satisfied.


References
-    Wagner, F.M., Mollaret, C., Günther, T., Kemna, A., & Hauck, C. (2019). Quantitative imaging of water, ice, and air in permafrost systems through petrophysical joint inversion of seismic refraction and electrical resistivity data. Geophysical Journal International, 219(3), 1866–1875. doi:10.1093/gji/ggz402.
-    Günther, T., & Rücker, C. (2008). A new joint inversion approach applied to the combined tomography of DC resistivity and seismic refraction data. Symposium on the application of geophysics to engineering and environmental problems 2006 (pp. 1196–1202). doi:10.4133/1.2923578.

How to cite: Pavoni, M., Boaga, J., Wagner, F., Bast, A., and Phillips, M.: Combined use of structurally-coupled and petrophysically-coupled joint inversion for the characterization of rock glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5861, https://doi.org/10.5194/egusphere-egu22-5861, 2022.

11:22–11:27
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EGU22-12621
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On-site presentation
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Thomas Günther, Janek Greskowiak, Nele Grünenbaum, Nico Skibbe, and Thomas Vienken

Imaging saltwater/freshwater interfaces is of importance to understand flow and transport in coastal aquifers. For hydrogeophysical imaging the method of electrical resistivity tomography (ERT) yields high-resolution images and is suited for monitoring. However, there is an intrinsic ambiguity in the inversion of the data that limits accurate quantification. In contrast, direct push (DP) data provide accurate point information. Moreover, DP fluid sampling helps to transfer the measured electrical conductivity into salinity by computing a spatially variable formation factor. Both data show typically the same structures but contradict in detail.
We present a methodology to combine both methods using joint inversion. To this end, DP data are treated like geophysical data with standard deviations derived from statistics so that the resistivity distribution strives to match the DP data at the given point. Additionally, the spatial distribution of DP data can be used to derive geostatistical correlation lengths in the horizontal and vertical directions that are incorporated into the ERT inversion using an anisotripic geostatistical regularization operator. Synthetic modellings with geostatistical media show that the ERT image is improved, not only in the vicinity of the sampling points.
We present data from the northern beach of the North Sea island of  Spiekeroog where we want to image the circulation cell that formes under the influence of the tides (upper saline plume). There is a significant improvement of the classical smoothness-constrained inversion compared to the DP-guided inversion. As a result, we observe a split into several circulation cells with local groundwater discharge zones. Our hypothesis is that these are mainly driven by the changing beach morphology.

How to cite: Günther, T., Greskowiak, J., Grünenbaum, N., Skibbe, N., and Vienken, T.: Improved hydrogeophysical imaging with ERT using direct push data as priors and geostatistical regularization, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12621, https://doi.org/10.5194/egusphere-egu22-12621, 2022.

11:27–11:32
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EGU22-10924
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ECS
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Virtual presentation
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Pankaj Kumar Gupta, Behrad Gharedaghloo, and Jonathan S. Price

Increasing hydrocarbon resource developments in and around peatlands impose risks of petroleum hydrocarbon spills on these important wetland landscapes. Despite the potential severity of consequences, there is a big gap of knowledge on parameter values controlling liquid hydrocarbons’ redistributions in peat soil after a spill. Complete excavation of contaminated peat soil is a common practice in contaminated sites, but destroys wetland function, and contributes nothing to the understanding of the problem. To partially fill this knowledge gap and to examine potential remediation strategies that are less destructive, we examined the fate, transport, and degradation of petroleum hydrocarbon non-aqueous phase liquids (NAPLs) in peat soils using a series of column tests on intact peat monoliths. Three-phase flow experiments with numerical simulations provided values of multiphase flow parameters that control NAPL redistribution in a variety of peat soils. We observed that water table fluctuations reduced residual NAPL saturation from 8.1-11.3% to 7.7-9.5%; increased headspace concentrations of n-C8 and n-C12 an average 163.7% and 13.4%, due to volatilization. Results also illustrated that water table dynamics promoted growth (from 104 CFU/gram to 106 CFU/gram peat) of specialized microbial communities in NAPL polluted peat columns. These results suggest that water table fluctuation can be a suitable tool for physical and microbial NAPL removal in peat soils, and for the first time provide evidence for it. We also observed a high ratio of Proteobacteria to Acidobacteria in the NAPL contaminated zone, which can be linked to the restoration success for a NAPL polluted peatland. The results could help environmental scientists in forecasting the behavior of spilled non-aqueous phase liquids (NAPLs) in peatland.

How to cite: Gupta, P. K., Gharedaghloo, B., and Price, J. S.: Understanding hydrocarbon fate and transport in peat soils using column experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10924, https://doi.org/10.5194/egusphere-egu22-10924, 2022.

11:32–11:37
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EGU22-7568
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ECS
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On-site presentation
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Alberto Carrera, Mirko Pavoni, Ilaria Piccoli, Jacopo Boaga, Giorgio Cassiani, and Francesco Morari

 

One of the major threats to global arable lands is represented by soil compaction, mainly due to agricultural traffic. Modern heavy agricultural machinery and unsuitable soil moisture conditions might irreversibly induce soil compaction that, in turn, adversely affects soil quality and ecosystem. Restriction to root penetration alongside impaired water and air fluxes are a few principal drawbacks of compacted soils, resulting in significant ecological and economic damage to society.
However, traditional methods to study soil compaction are limited by punctual nature and not-in-situ conditions.
In this context, the purpose of this work was to combine different non-invasive geophysical techniques, with a joint inversion approach of the acquired datasets, to study the complexity of the soil structure. In detail, we tried to adapt the petrophysical joint inversion developed in permafrost systems, combining geoelectrical and seismic soundings to characterize the subsoil structure in compacted and non-compacted soils. This methodology rests on the conjunction of seismic refraction tomography (RST) and electrical resistivity tomography (ERT), acquired on the very line, through a representative pedophysical model, able to quantitatively estimate the fractions of investigated soil phases (e.g., air, water, and matrix fractions).
The survey was conducted on an arable field of “L. Toniolo” Padova University experimental farm. The reliability of the obtained models was compared with direct measurements of volumetric water content, bulk density, and penetration resistance along the survey line. Preliminary results showed that the methodology might be a promising tool for spatio-temporal evaluation of soil structure evolution as related to soil compaction.

How to cite: Carrera, A., Pavoni, M., Piccoli, I., Boaga, J., Cassiani, G., and Morari, F.: Soil compaction imaging through Pedophysical Joint Inversion: a Northeastern Italy case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7568, https://doi.org/10.5194/egusphere-egu22-7568, 2022.

11:37–11:42
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EGU22-10243
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ECS
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Presentation form not yet defined
Interactive training methods to promote knowledge and raise awareness of the wider educational community on issues regarding technological and natural disasters 
(withdrawn)
Anthi Eirini Vozinaki, Aggeliki Christaki, Maria Papadaki, and Aggeliki Vidali
11:42–11:50