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ABSTRACT

The flux of atmospheric/soil CO2 consumed by chemical weathering of the continents (FCO2) can be estimated from river fluxes of bicarbonates. Using published data for 232 small monolithologic watersheds, empirical relationships between FCO2 and runoff (Q) have been determined for the major rock types outcropping on the continents. For validation, the models fitted to these relationships are applied to the Garonne, Congo and Amazon river basins to calculate the average CO2 consumption on these large river basins; the model results are close to previous estimates based on field measurements. The model (GEM-CO2: Global Erosion Model for CO2 fluxes) is then applied at the global scale and allows the determination of latitudinal variations of the consumption of atmospheric/soil CO2 by chemical erosion. The main results show that the consumption of CO2 is mainly localized in the Northern hemisphere, because of large continental area with a high proportion of carbonate rocks, and in equatorial regions which are very humid. Finally, the mean annual CO2 consumption for the whole continents amount to 0.26 Gt C y−1, and 72% of this flux is removed in the Northern hemisphere.