High chemical weathering rates in first-order granitic catchments induced by agricultural stress

Chemical erosion rates have been determined on two upland granitic catchments under agricultural pressure in Brittany, France. Intensive agriculture has been carried out for at least 30 years in this region. The influence of geochemical processes related to agriculture on the chemistry of streamwaters is determined through a geochemical mass balance. The elemental export fluxes from these two agricultural catchments are then compared with other catchments around the world.