The role of hydrology on enhanced weathering for carbon sequestration II. From hydroclimatic scenarios to carbon-sequestration efficiencies

Enhanced weathering (EW) scenarios are analyzed using the model presented in Cipolla et al. (2020). We explore the role of different hydroclimatic forcing on carbon-sequestration efficiencies. We also investigate whether increasing soil carbon content improves weathering conditions. We link olivine weathering rates to pH variations and quantify the suitability of hydroclimatic regimes to EW, based on rainfall intensity and frequency. The results show that the amount of CO2 reacting with olivine and ending up in solution in the form of HCO3- and CO32- increases with mean annual precipitation (MAP) up to 2000 mm, but then tapers off for higher MAPs. On the contrary, the sequestered CO2 continues to grow with MAP in a more significant way. We also quantify the increase of nutrients availability, especially when MAP exceeds 2000 mm. Lastly, the results suggest that organic matter amendments are more effective in humid environments (MAP higher than 2000 mm), confirming the central role of hydrologic processes on EW.