Rapid CO2 consumption during incipient weathering of a granular basaltic hillslope in the Landscape Evolution Observatory, Biosphere 2.

Abstract:

Carbon uptake from the atmosphere during basalt weathering is an important control on global carbon cycling on geologic time scales. Indeed, the use of crushed olivine or basalt has been proposed as a geoengineering solution to provide a mechanism to offset human emissions. We present carbon sequestration, gas and solution phase, data collected in a landscape-scale (11 x 30 m hillslope, 1 m depth) experiment with crushed basalt under ambient conditions. The Landscape Evolution Observatory (LEO) provides a landscape scale – but highly controlled – experimental system that enables quantification of carbon dioxide consumption during initial weathering of a granular basaltic substrate. We found that simulated rainfall induces an immediate depletion of the CO₂ concentration within the soil pore network and that the overall inorganic carbon content within the matrix is well predicted by initial inorganic carbon content, that added from the atmosphere and that exported by seepage flow. Rates of CO₂ uptake are comparable to global estimates for basalt, but lower than those currently predicted by advocates for using olivine to sequester carbon dioxide from the atmosphere.