Résumé
The DOM fluorescence property has been used as a natural tracer in different water systems. However, only few studies focused on groundwater systems, notably on karstic ones. The aim of this study is to develop the use of the DOM fluorescence signal as a natural tracer, considering the multiple compartments of a karst system. This method was applied to the Lez hydrosystem, which the Lez spring supplies the city of Montpellier with drinking water. Hydrodynamic and hydrochemistry were monitored since March 2006 at the spring. The DOM fluorescence was measured with the Excitation-Emission Matrices (EEM) spectroscopy technique. On one hand, the analysis of the total fluorescence signal confirms the efficiency of this tool to trace rapid infiltration flows. On the other hand, the ecomposition of the signal in different fluorophores complements the information provided by the total signal. Indeed, the fluorescence emitted by humic compounds seems to be the best adapted tool to identify rapid infiltration flows. Nevertheless, the fluorescence of proteinlike compounds is better correlated with the inflow of faecal bacteria at the outlet. This decomposition of the fluorescence signal is an interesting way to provide information both on the characterization of rapid infiltration flow and on karst aquifers vulnerability.