Relationship between hydraulic properties and material features in a heterogeneous vadose zone of a vulnerable limestone aquifer

Abstract

Limestone aquifers constitute important drinking water resources but are vulnerable to groundwater contaminations. They are also known to be often heterogeneous. However, the hydraulic properties of their entire vadose zone and the relationship of these hydraulic properties with their mineralogical and geochemical characteristics remain rarely studied. The hydraulic properties of soft (soil, powdery limestone, and calcareous sand) and hard (limestone rock) materials sampled throughout the entire vadose zone profile of the Beauce limestone aquifer (France) were determined with

Integrated static and dynamic geophysical and geomechanical data for characterization of transport properties

“…Meanwhile, this centimetric size of REV seems well to account for the microporosity and the micro-cracks, and avoid the boundary effects when considering clasts and a network of karst conduits. In these REV, the presence of heterogeneities, which are the focus of this study, have been confirmed by optical microscopy and Scanning Electron Microscopy (SEM) [Aldana, 2019;Aldana et al, 2021]. Table 1 gives indications about the length and aperture of the observed macroscopic features observed and measured on log, core samples and through optical microscopy and SEM (Figure 2).…”

“…The enhancement of this heterogeneity network could be attributed to the apparition of downstream altered rock. Indeed, from this depth, the limestone alteration is increased by the variations of the water table level (which has already reached a depth of 15 m over the last few decades) and footprints of water/rock interactions [Aldana et al, 2021].…”

“…The hydraulic properties of undisturbed cored samples from B2 have been already determined on previous studies made by Aldana [2019] and Aldana et al [2021], using a multistep outflow method applied by using a triaxial system. The values of saturated hydraulic conductivity, K S were obtained in m.s −1 .…”

“…The first geophysical monitoring campaigns (especially with log imaging) and the direct core observations highlighted that this observatory is taking place in hard limestone rock formations affected by upstream and downstream alterations, micro-pores and cracks, macro-fracturation, and karstification [Aldana et al, 2021]. A specific lithological log is proposed in Figure 1B [Mallet et al, in press].…”

“…• 0.0-1.5 m: silt loam soil typical of the Beauce region [Ould Mohamed et al, 1997;Aldana et al, 2021].…”