Influence of acid rain on CO2 consumption by rock weathering: Local and global scales

Sulphuric and nitric acids, which are supplied by acid precipitation, take over from carbonic acid in weathering reactions, which induced a decrease of the atmospheric/soil CO2 consumption by weathering (WCO2). In order to quantify this disturbance, one has compared the bicarbonate fluxes determined at the outlet of 2 small catchments (one is substantially disturbed and the other is is weakly disturbed by acid precipitation). Our study shows that, under the influence of acid precipitation, bicarbonate fluxes (i.e. WCO2) are decreased by about 73%. It has also been attempted to simulate at the continental scale, the influence of acid precipitation on WCO2, using a Global Erosion Model (GEM-CO2) recently developed. Several simulations have been performed corresponding to different realistic scenarios of global acid precipitation. In the most pessimistic of these scenarios, the GEM-CO2 simulation shows that the global WCO2 would be decreased by no more than 10%.