Noninvasive Imaging of Processes in Natural Porous Media: From Pore to Field Scale

Abstract

Core Ideas Noninvasive, high‐resolution imaging is important for visualizing water flow and transport processes. Most important are X‐ray CT, MRI, and neutron CT. Image processing techniques are mandatory for maximum benefit from the images. Noninvasive, high‐resolution imaging techniques are important for visualizing water flow and transport processes in soils, which are natural porous media. They are a key to understanding effects such as crop production, water resource restoration, CO2 sequestration, or the transport and fate of pollutants. During the last two decades, the development of three‐dimensional imaging techniques such as nuclear magnetic resonance imaging (NMR and MRI), X‐ray computed tomography (CT), and neutron CT has made significant progress possible in the study of soil processes. This special section presents examples of X‐ray CT and NMR from the small‐column scale to the application of portable NMR equipment in the field, along with some important advances in image processing that make it possible to extract optimal physical information from the original data.

Dynamic NMR Relaxometry as a Simple Tool for Measuring Liquid Transfers and Characterizing Surface and Structure Evolution in Porous Media

“…In this context, various techniques such as permeability measurements, mercury porosimetry, and sorption–desorption tests can be used to obtain different types of information concerning the structure or the flow processes inside a porous medium, but the most powerful techniques − are X-ray, neutron, and MRI (magnetic resonance imaging). High-resolution X-ray tomography allows us to obtain detailed views of the evolution of the fluid–solid interfaces at the pore scale in nontransparent porous media …”

Water Retention and Pore Size Distribution of a Biopolymeric‐Amended Loam Soil

“…The study of the impact on PSD is usually neglected in soil amendment experiments because it is difficult to quantify by classical field/laboratory methods, including direct or indirect measurement of PSD from water retention curve (WRC) measurements based on soil water content or geophysical measurements and hydrological inversion (as done by Jadoon et al, 2012; Busch et al, 2013; and Jonard et al, 2015) or WRC measured by pressure plate extractors (e.g., Bittelli and Flury, 2009); multistep outflow (e.g., Bayer et al, 2005; Hollenbeck and Jensen, 1998; Neyshabouri et al, 2013; Weihermüller et al, 2009); or the evaporation (e.g., Schindler et al, 2010; Žydelis et al, 2018), mercury intrusion (e.g., Webb, 2001), and nitrogen sorption (e.g., Kowalczyk et al, 2003) methods. As an alternative, noninvasive measurement techniques can be used, such as MicroCT (e.g., Koestel, 2018; Pohlmeier et al, 2018; Smet et al, 2017), synchrotron radiation and/or microtomography (e.g., Peth et al, 2008), or nuclear magnetic resonance relaxometry (NMRR) (e.g., Jaeger et al, 2009; Stingaciu et al, 2010).…”

Monitoring Preferential Flow of Water in Sand Using Thermoacoustics Wave Imaging

“…Understanding the distribution of fluid phases during multiphase flow in porous media is critical in a wide array of subsurface natural processes and engineering applications (Berg et al., 2013; Blunt et al., 2013; Jarvis, 2007). Optical imaging, X‐ray tomography, and magnetic resonance imaging (MRI) are just a few of the most commonly used non‐invasive, high‐resolution imaging techniques (Cnudde & Boone, 2013; Katuwal et al., 2018; Pohlmeier et al., 2018). However, these methods are subject to important drawbacks that not only limit their use in field applications but also in controlled laboratory environments (Werth et al., 2010; Wildenschild et al., 2002).…”