Quantification of conservative and reactive transport using a singlegroundwater tracer test in a fractured media

International audience; dentification of biogeochemical reactions in aquifers and determining kinetics is important for the predictionof contaminant transport in aquifers and groundwater management. Therefore, experiments accounting for bothconservative and reactive transport are essential to understand the biogeochemical reactivity at field scale.This study presents the results of a groundwater tracer test using the combined injection of dissolved conservativeand reactive tracers (He, Xe, Ar, Br-, O2and NO3-) in order to evaluate the transport properties of a fracturedmedia in Brittany, France.Dissolved gas concentrations were continuously monitored in situ with a CF-MIMS (Chatton et al, 2016) allowinga high frequency (1 gas every 2 seconds) multi-tracer analysis (N2, O2, CO2, CH4, N2O, H2, He, Ne, Ar, Kr, Xe)over a large resolution (6 orders of magnitude). Along with dissolved gases, groundwater biogeochemistry wasmonitored through the sampling of major anions and cations, trace elements and microbiological diversity.The results show breakthrough curves allowing the combined quantification of conservative and reactive transportproperties. This ongoing work is an original approach investigating the link between heterogeneity of porousmedia and biogeochemical reactions at field scale.Eliot Chatton, Thierry Labasque, Je ́roˆme de La Bernardie, Nicolas Guihe ́neuf, Olivier Bour and LucAquilina; Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics andBiogeochemistry of Groundwater Flow; Environmental Science & Technology, in press, 2016.