Enhanced weathering potentials—the role of in situ CO2 and grain size distribution

The application of rock powder on agricultural land to ameliorate soils and remove carbon dioxide (CO 2 ) from the air by chemical weathering is still subject many uncertainties. To elucidate effects grain size distribution soil partial pressure ( p CO levels uptake rates, two simple column experiments were designed filled nearly daily with an amount water that simulates humid tropical conditions, which prevail in areas known for being hotspots weathering. Multiple materials (dunite, basanite, oxisol, a combination latter two, loess) compared under ambient 100% atmosphere. In second series, single material columns (dunite) three different distributions. Total alkalinity, pH, major ions, dissolved silica determined outflow about 300 days. Under atmospheric consumption was lowest oxisol column, 100 t km −2 year −1 , while dunite basanite showed similar rates (around 220 ). values are comparable high literature ultramafic lithologies. Interestingly, mixture has much higher rate 430 than alone. fluxes saturated conditions four times all columns, except where increased factor more eleven. Grain differences also play role, highest surface area normalized observed coarser grains, at first seems counterintuitive. Our findings point some important issues be considered future potential rollout EW as removal method. Only theory do small sizes spread-material yield drawdown potentials material. hydrologic determine residence pore space, i.e., time available reactions, can size. Saturated-CO results provide upper limit elevated .