Key Parameters Controlling the Seasonal and Inter-annual Variations of pCO2, Chemical Composition and Carbonate Equilibrium in Stream Water from a Mountainous Karstic Catchment (Pyrenees, France)

The carbonate dissolution plays a major role in the atmospheric CO2 sink and in the riverine transfer of dissolved inorganic carbon from the atmosphere to the critical zone and to the oceans. In this context, the Baget watershed (13.25 km2, altitude 950 m), essentially forested and weakly exposed to local anthropogenic pollution, drains a karst area in the Pyrenees mountains. It has been monitored for more than 40 years to better understand the impact of global changes on carbonate dissolution and hydro-chemistry of streamwaters. The mean annual precipitation exceeds 1500 mm and the air temperature average is 12°C. Calcareous dominates the lithology (around 2/3 of the area), with some flysh and schists. This experimental catchment belongs to the French Karst Network, to the French (OZCAR) and European (LTER) Research Infrastructures. Based on the hydrochemistry survey since 1978, the results focus on carbonate dissolution, stream water chemistry (mainly Ca, Mg and alkalinity) and calcite saturation index ...