Quantitative mapping of solute accumulation in a soil‐root system by magnetic resonance imaging

Abstract

Differential uptake of water and solutes by plant roots generates heterogeneous concentration distributions in soils. Noninvasive observations of root system architecture and concentration patterns therefore provide information about root water and solute uptake. We present the application of magnetic resonance imaging (MRI) to image and monitor root architecture and the distribution of a tracer, GdDTPA2− (Gadolinium‐diethylenetriaminepentacetate) noninvasively during an infiltration experiment in a soil column planted with white lupin. We show that inversion recovery preparation within the MRI imaging sequence can quantitatively map concentrations of a tracer in a complex root‐soil system. Instead of a simple T1 weighting, the procedure is extended by a wide range of inversion times to precisely map T1 and subsequently to cover a much broader concentration range of the solute. The derived concentrations patterns were consistent with mass balances and showed that the GdDTPA2− tracer represents a solute that is excluded by roots. Monitoring and imaging the accumulation of the tracer in the root zone therefore offers the potential to determine where and by which roots water is taken up.

Combination of MRI and SEM to Assess Changes in the Chemical Properties and Permeability of Porous Media due to Barite Precipitation

“…The permeability change derived from porosity/permeability relaxometry relationship, in agreement with independent experimental measurements, was substantial, highlighting the impact of the localized clogging zone and pore throat reduction (observed during SEM investigation), which would reduce the pore connectivity. Further work will focus on the investigation of the pore connectivity using low field 2D relaxometry [40].…”

“…They obey Equation 2and thus allow specific statements about the local properties of the porous medium. In this work, we employed T 1 and T 2 relaxation time mapping by a combination of the spatially resolved MRI signal with either an inversion recovery preparation [39] or CPMG echo train decoding [40]. Especially, the obtained T 2 maps allowed the monitoring of the progress of the reaction due to the sensitivity of T 2 on the conversion from celestine to barite.…”

“…The evaluation proceeded by complex division of the scans with IR preparation by the reference scan. This procedure benefits from the full range of the IR prepared signal from −1 to +1 for the real part of the complex image and the avoidance of cross-talk effects [40]. Additionally, fresh and fully reacted columns were scanned separately to determine the respective T 1 and T 2 relaxation times.…”

Combination of Magnetic Resonance Imaging and Neutron Computed Tomography for Three‐Dimensional Rhizosphere Imaging

“…The T 1 maps were calculated from a series of single echo multislice (SEMS) images with inversion recovery preparation, using inversion times t inv of 0.1, 0.2, 0.4, 0.8, and 1.6 s plus a reference image with no inversion recovery preparation. For details, see Haber‐Pohlmeier et al (2017). Here only the most important sequence parameters are given as t R = 8 s, t E = 4 ms, FOV = 60 by 60 by 66 mm, matrix size = 256 by 256, and 30 slices of 2‐mm thickness with a gap of 0.2 mm, which corresponds to a voxel resolution of 234 μm by 234 μm by 2.2 mm.…”

Investigating the impact of exit effects on solute transport in macropored porous media

“…Due to its paramagnetic properties, Gd 3+ is known to be an excellent MRI contrasting agent (Pyykkö, 2015), and has already been used to study solute transport in soils (Haber-Pohlmeier et al, 2017).…”