Real time in situ dissolved gases monitoring in groundwater by CF-MIMS for hydrogeology
Abstract
We present an optimized Continuous Flow -
Membrane Inlet Mass Spectrometer (CF-MIMS) for
in situ real time monitoring of dissolved gases in
groundwater. Our system allows continuous
measurements of nobles gases (He, Ne, Ar, Kr and
Xe) and CO2, O2, N2, N2O, H2, CH4 in water. A large
membrane introduction system and an adapted
ionisation procedure allow our system to measure all
gases every 15s or one gas every 1.5 s. We present
here the results of dissolved gases tracer tests in a
fractured aquifer as well as an in situ real time welllogging
of dissolved gases The high resolution
breakthrough curve of the dissolved gas tracer
improve our knowledge on transport characteristics in
fractured aquifers. High resolution profiles of
dissolved gases in boreholes inform us about
stratification of water masses, redox and recharge
conditions (NGT, Excess air) and allow 4He age
estimation.
This breakthrough in the measurement of
dissolved gases (in situ monitoring and high
frequency) is very promissing for physical, chemical
and biogeochemical studies in waters.