Advances in field noble gas measurements towards operational hydrology
Abstract
In natural waters, noble gas concentrations are governed
by a diversity of relatively simple and well-studied physical
processes. As a result, noble gas measurements provide
important information on various phenomena such as
groundwater residence time distribution (4He, 21Ne, 37Ar, 39Ar,
40Ar, 85Kr, 81Kr), aquifer recharge conditions (temperature,
elevation …) or aquifer-river exchange (222Rn).
However, despite their interest, noble gas data remain
relatively scarce and punctual owing to the complexity and
costs of their production. In view of the spatial and temporal
variety and variability of the Hydrosphere dynamics a new
investigation method is needed.
This study approaches the concept of “operational
hydrology” aiming to enhance both the spatio-temporal
distribution and the quality of environmental data for a
thorough exploration of the Hydrosphere.
In this perspective, we developed a new analytical tool
based on membrane inlet mass spectrometry (MIMS)
allowing the continuous measurement of dissolved gases
(Chatton et al., 2017).
To illustrate our approach, we present atmospheric and
radiogenic noble gas data (He, Ne, Ar, Kr, Xe) measured in
situ with a CF-MIMS (Chatton et al, 2017) installed in a
mobile laboratory arranged in an all-terrain truck (CRITEXLab).
This ongoing work focuses on groundwater and the
field investigation of residence time distribution, recharge
processes, water flow paths and mixing.