Abstract
Abstract. The effect of macropore flow on solute transport has spurred much research over the last forty years. In this study, non-reactive solute transport in water-saturated columns filled with porous media crossed by a macropore was experimentally and numerically investigated. The emphasis was put on the study of exit effects, whose very existence is inherent to the finite size of any experimental column. We specifically investigated the impact of a filter at the column outlet on water flow and solute transport in macroporous systems. Experiments involving breakthrough measurements and magnetic resonance imaging (MRI) showed that solute transport displayed some significant non-unidirectional features, with a strong mass exchange at the interface between the macropore and the matrix. Fluid dynamics and transport simulations indicated that this was due to the non-unidirectional nature of the flow field close to the outlet filter. The flow near the exit of the column was shown to be strongly impacted by the presence of the outlet filter, which acts as a barrier and redistributes water from the macropore to the matrix. This impact was apparent on the breakthrough curves and the MRI images. It was also confirmed by computer simulations and could, if not properly taken into account, impede the accurate inference of the transport properties of macroporous media from breakthrough experiments.
Highlights
Column experiments are frequently performed to study the transport of various contaminants in soils (De Matos et al, 2001; Pang et al, 2002; Banzhaf and Hebig, 2016; Jin et al, 2000) or to fit experimental data with a transport model (Nielsen and Biggar, 1961; De Smedt and Wierenga, 1984; Cortis and Berkowitz, 2004)
This paper aims to demonstrate the significant influence of an outlet filter on water flow and non-reactive solute transport within an artificial macroporous system
Using a combination of breakthrough experiments, magnetic resonance imaging (MRI) monitoring and computer simulations, we show that water flow and non-reactive solute transport in water-saturated macroporous media are strongly affected by the presence of a filter at the end of the column
Summary
Column experiments are frequently performed to study the transport of various contaminants in soils (De Matos et al, 2001; Pang et al, 2002; Banzhaf and Hebig, 2016; Jin et al, 2000) or to fit experimental data with a transport model (Nielsen and Biggar, 1961; De Smedt and Wierenga, 1984; Cortis and Berkowitz, 2004). The general motivation shared by all these experiments is to study and to understand the transport processes occurring in the bulk of a porous medium in a simple and reproducible setting by imposing a stationary flow along the axis of the column. This task is more challenging than it might appear at first sight. The finite size of the column can impact water flow and solute transport with, for instance, the existence of entrance–exit effects affecting the uniformity of the flow near the extremities of a column (Koestel and Larsbo, 2014; Flury et al, 1999; Starr and Parlange, 1977; Bromly et al, 2007). The breakthrough curves (BTCs) may be affected by entrance–
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
