title: Imaging water fluxes in porous media by magnetic resonance imaging using D(2)O as a tracer.
abstract: In this study, we investigate the usefulness of D(2)O as a conservative tracer for monitoring water flux by MRI in a heterogeneous sand column. The column consisted of a cylindrical 3x9-cm packing of fine sand in which an 8-mm diameter cylindrical obstacle was placed. Constant steady-state flux densities between J(w)=0.07 and 0.28 cm min(-1) corresponding to mean pore flow velocities between 0.20 and 0.79 cm min(-1) were imposed at the top of the sand column, and a constant hydraulic head of -39 cm was maintained at the lower boundary. We injected pulses of 0.01 M NiCl(2) and 55% D(2)O and monitored the motion of the tracer plumes by MRI using a fast spin echo sequence over a period of 20 min. We observed that the center of gravity of all plumes moved with the mean pore flow velocity, which showed that D(2)O behaves as a conservative tracer. The motion of the tracer plume at J(w)=0.14 cm min(-1) was validated by a numerical simulation using HYDRUS2D, which reproduced the experimentally observed behavior very satisfactorily.
authors.affiliation: Forschungszentrum Jülich, ICG-4, Jülich 52425, Germany. a.pohlmeier@fz-juelich.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Pohlmeier
authors.forename: Dagmar
authors.initials: D
authors.lastname: van Dusschoten
authors.forename: Lutz
authors.initials: L
authors.lastname: Weihermüller
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schurr
authors.forename: Harry
authors.initials: H
authors.lastname: Vereecken