Drying of a Natural Soil Under Evaporative Conditions: A Comparison of Different Magnetic Resonance Methods

Merz, Steffen; Pohlmeier, Andreas; Balcom, Bruce J.; Enjilela, Razieh; Vereecken, Harry

doi:10.1007/s00723-015-0736-6

Cited by 13 publications

(15 citation statements)

References 33 publications

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“…The MRI technique has been applied to measure near-surface soil moisture distributions at the millimeter scale (Merz et al, 2015(Merz et al, , 2016. Furthermore, MRI images can be distorted due to the inherent fast relaxation times in natural soils with high clay content and paramagnetic impurities (Merz et al, 2016). Furthermore, MRI images can be distorted due to the inherent fast relaxation times in natural soils with high clay content and paramagnetic impurities (Merz et al, 2016).…”

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confidence: 99%

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High‐Resolution Shortwave Infrared Imaging of Water Infiltration into Dry Soil

Sadeghi

Sheng

Babaeian

et al. 2017

Vadose Zone Journal

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Core Ideas SWIR imaging for quantification of soil moisture dynamics is introduced. High spatiotemporal resolution images yield accurate soil moisture profile. Flux density profiles during water infiltration were quantified with this method. The new technique opens potential avenues for soil hydraulic properties estimation. A novel proximal sensing framework for high‐resolution soil water content profile retrieval under laboratory conditions has been developed. Constant‐head upward‐flow experiments were conducted for a number of soils that cover a wide textural range. The soils were packed into quartz Hele–Shaw cells, and the profile was imaged at high temporal frequency with a shortwave infrared (SWIR) camera in the 900‐ to 1700‐nm electromagnetic domain during upward infiltration of water. The SWIR reflectance recorded for each spatial pixel was converted to soil water content with a recently developed linear physical model. Because of the linearity of the model, its parameters were assumed to be identical at both the pixel and column scales, and this allowed simple self‐calibration during the experiment. The obtained water content profiles were in good agreement with soil water content data measured independently with a recently developed time domain reflectometry array with 1‐cm depth resolution. In addition, the accuracy of the soil water content profiles was verified based on the water mass balance. The high‐spatiotemporal‐resolution SWIR reflectance‐derived water content profiles allow calculation of water flux densities, which provides a potential new avenue for the rapid estimation of soil hydraulic properties and processes via inverse numerical or analytical modeling.

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confidence: 99%

“…However, MRI techniques do not always provide absolute moisture values, especially at low saturation levels (Gilbert and Deinert, 2013). Furthermore, MRI images can be distorted due to the inherent fast relaxation times in natural soils with high clay content and paramagnetic impurities (Merz et al, 2016).…”

mentioning

confidence: 99%

High‐Resolution Shortwave Infrared Imaging of Water Infiltration into Dry Soil

Sadeghi

Sheng

Babaeian

et al. 2017

Vadose Zone Journal

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“…Lowering of the hydraulic head to h = −20 cm resulted in a more pronounced profile between 0.37 cm 3 /cm 3 at the bottom to 0.1 cm 3 /cm 3 at a depth of -0.2 cm. A shallow dry layer developed on the surface which caused a significant reduction of the evaporation rate due to loss of capillary continuity (Merz et al 2016;Shokri et al 2010). These different scenarios resulted in different evaporation rates Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Immediately after excitation, the precessing magnetization decays with two relaxation processes termed as T 1 and T 2 . For the sake of simplicity, we restrict on NMR of liquids in the following, for details please refer to the literature (Blümich 2000;Blümich et al 2014;Callaghan 1991;McRobbie et al 2007). The relaxation times as well as the signal depend on the water content of the sample, the interaction of the liquid with its chemical and physical surroundings, and of the local diffusional and translational motion.…”

Section: Methodsmentioning

confidence: 99%

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Quantitative imaging of sodium concentrations in soil-root systems using magnetic resonance imaging (MRI)

et al. 2020

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Aims Demonstrating the potential of MRI as a 3D, non-invasive and continuous measurement technique to map Na+ concentration distributions in soil and around roots. Methods Dissolved NaCl in soil and soil-plant systems was mapped by 3D 23Na-MRI. The lower limit of detectability in saturated and unsaturated porous media was evaluated, followed by evaporation experiments to test the quantification. Finally, Na+ enrichment around tomato roots, irrigated with saline solution under low/high transpiration rates (LT, HT), was imaged in parallel to the root system,. Results A spin echo pulse sequence allowed the quantitative mapping of the volume concentration of NaCl in sandy porous medium. Evaporation experiments showed slight enrichment in the top surface layer, plus uniform temporal enrichment in the deeper layers. In the tomato experiments, enrichment was more distinct under HT than under LT. Concentration-distance correlation curves revealed thin enrichment zones ranging a few mm around the roots. Conclusions MRI can map Na+ non-invasively in 3D at relevant concentrations for root activity. Visualizing water content, roots and Na+ on the same scale is possible, despite limitations of different scanning times and resolution. This opens a route for further quantitative investigations of salt enrichment processes in soil and soil-plant systems.

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Biohydrogel induced soil–water interactions: how to untangle the gel effect? A review

Brax

Buchmann

Schaumann

2017

J. Plant Nutr. Soil Sci.

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Biohydrogels such as microbial exudates and root‐derived mucilage are soil‐born cross‐linked polymers, able to form porous three‐dimensional networks during water uptake. The gel effect is the variation of soil properties, such as soil hydrology and soil structural stability, resulting from biohydrogel swelling in soil. Conventionally, soil–water–hydrogel interactions are investigated by measuring soil bulk properties such as water retention curves and porosity, without further analyzing the effect of biohydrogel phases in soil on a quantitative basis. Therefore, the evaluation of advanced and novel methods for the characterization of biohydrogel phases in soil and soil–water–hydrogel interactions is necessary. This review evaluates currently available methods for their potential to analyze processes associated to the gel effect. A promising approach to investigate the spatio‐temporal distribution of biohydrogel phases in porous media is based on Nuclear Magnetic Resonance (NMR) such as 1H‐NMR relaxometry, as well as on imaging techniques such as Environmental Scanning Electron Microscopy (ESEM). Especially NMR techniques enable the identification of different water populations based on their differences in the relaxation, and thus the mobility of water molecules in biohydrogels and non‐gel water in soil pores. Rheology measures the flow behavior of biohydrogels, providing information on the structural behavior of the hydrogel network and its gelling mechanism. Soil rheology further quantifies the effect of the biohydrogel phases on the interactions between soil particles, and thus the impact on soil microstructural stability. However, rheology does not elucidate the spatio‐temporal distribution and structural state of biohydrogel phases in soil. All in all, a systematic combination of rheology, NMR and suitable imaging methods seems promising and necessary in order to elucidate the still widely unknown gel effect in soil.

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Drying of a Natural Soil Under Evaporative Conditions: A Comparison of Different Magnetic Resonance Methods

Cited by 13 publications

References 33 publications

High‐Resolution Shortwave Infrared Imaging of Water Infiltration into Dry Soil

High‐Resolution Shortwave Infrared Imaging of Water Infiltration into Dry Soil

Quantitative imaging of sodium concentrations in soil-root systems using magnetic resonance imaging (MRI)

Biohydrogel induced soil–water interactions: how to untangle the gel effect? A review

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