Étude des facteurs influençant le relargage et la transformation du mercure dans des réservoirs hydroélectriques

Abstract

Due to increased mercury concentrations in fish in hydro-electric reservoirs after flooding, a study was carried out to evaluate the release and transformation of mercury due to vegetation and soil flooded as a result of reservoir creation. Samples of vegetation and soils were immersed in water and concentrations of total mercury, methylmercury, and nutrients were followed. The effects of anoxia, pH, and temperature on release and transformation were also examined. An existing dynamic model of decomposition of flooded materials in reservoirs was modified to include mercury release and transformation, and was calibrated to the experimental data. Amounts of total mercury released by the different substrates were of the same order of magnitude. Tree species contributed the greatest amounts of methylmercury per unit biomass, but the biomass used for these was twigs and foliage. Soil released significant amounts of mercury, but methylation was very low. The model was able to fit well for all substrates except lichen. The model can be adapted to proposed reservoirs to predict nutrient and mercury release and transformation.