Mercury transport in Amazonian rivers. Case: Madre de Dios River-Perú

Abstract

The Amazon Rainforest is an iconic ecosystem, known for its diverse flora and fauna and large rivers that originate in the Andes and ultimately empty to the Atlantic Ocean. These rivers have been generally stable for thousands of years. However, the rapid expansion of gold mining within the Madre de Dios (MDD) basin is greatly threatening the physical processes that were once in equilibrium and the diverse aquatic and riparian habitats that the river provides. These activities have destabilized the drainage basin by increasing the amount of sediment being transported by tributaries and the main river. Additionally, the mining activities have resulted in a large influx of contamination (Mercury, Hg) to the river which is negatively affecting the water quality, riverine habitat, and the local communities. Hg preferentially attaches to fine-grained river sediment (cohesive material) and organic material that rivers carry in suspension. This study evaluates the role of the hydrodynamic pattern and the fine-grained sediment properties. Thus, this project seeks to address the use of remote sensing technology to determine the spatial and temporal variability in the concentration of suspended sediment along the MDD river and floodplain area. The preliminary results show distinct differences between high and low discharge seasons and that concentrations from tributaries directly affected by mining activities are higher than concentrations in the main channel. These findings have important implications for understanding how large-scale mixing processes are occurring throughout the system and potential areas that are at higher risk of contamination and bioaccumulation of Hg.