People involved:Virginie VERGNAUD (UR1), Thierry LABASQUE (CNRS), Luc AQUILINA (UR1), Olivier BOUR (UR1),  Tanguy LEBORGNE (UR1), Imène DJAROUD (UR1)


Radon analyses have been carried out in order to improve the understanding exchanges between surface and groundwater, as well as the spatial and temporal variability. Radon has been choosing as tracer to be presented in all water bodies that previously had been in contact with rocks. The 222Rn concentrations have been measured at Ploemeur experimental site (lake, rivers and piezometers) to monitoring the groundwater flux. To quantify the groundwater discharge to the surface water bodies a black box model has been used.This model considers the different radon input components (222Rn upstream flow, diffusive flow through the sediments, and groundwater contribution), and output (222Rn downstream flow, degassing 222Rn flow, decreasing 222Rn flux).

The study shows that the groundwater contribution to the surface drainage of Ploemeur is low in contrast with the East tributary. Downstream of the convergence between the East and West tributaries (out of the pumping site influence area) the groundwater contribution increases strongly.

Figure. Sampling points location and measured 222Rn concentration.