Mercury mobilization in soil from a rainfall event in a Tropical forest (French Guyana)

Mercury (Hg) distribution was achieved in a pristine Amazonian forested area during a rainfall event along a basin thalweg. Hg concentrations were measured in both surface runoff and underground waters and soils. Total Hg concentrations in the particulate and dissolved phase were related to the main hydrological processes in order to trace the fate of mercury during the flood event. Rainfall waters were also collected to assess the amount of Hg from atmospheric deposition and foliage leaching. Total Hg concentrations were found relatively homogenous over thé basin and were typical of remote area (9 ng l-1). In addition, air samples collected at the same site, at the ground level and at different heights (1-40m), which allowed us to determine temporal and spatial variability of total gaseous atmospheric Hg. Finally, dynamic flux chambers experiments were carried out to directly determine the exchanges of gaseous Hg at the soil/atmosphere interface, in order to better understand the role of the atmospheric compartment within the forest ecosystem.