Effects of precipitation seasonality, irrigation, vegetation cycle and soil type on enhanced weathering - modeling of cropland case studies across four sites

Enhanced weathering (EW) is a promising strategy for carbon sequestration, but several open questions remain regarding the actual rates of dissolution in conditions of natural hydroclimatic variability in comparison to laboratory experiments. In this context, models play a pivotal role, as they allow exploring and predicting EW dynamics under different environmental conditions. Here a comprehensive hydro-biogeochemical model has been applied to four cropland case studies (i.e., Sicily and the Padan plain in Italy and California and Iowa in the USA) characterized by different rainfall seasonality, vegetation (i.e., wheat for Sicily and California and corn for the Padan plain and Iowa), and soil type to explore their influence on dissolution rates. The results reveal that rainfall seasonality and irrigation when applied are crucial in determining EW and carbon sequestration dynamics, given their effect on hydrological fluxes, soil pH and weathering rate. The carbon sequestration rate was found to be strongly affected also by the background weathering flux, which is one of the main factors controlling soil pH before the olivine amendment. Regarding the US case studies, Iowa sequesters the greatest amount of CO2 if compared to California (4.20 and 2.21 kg ha(-)1 yr(-)1, respectively), and the same happens for Sicily with respect to the Padan plain (0.62 and 0.39 kg ha(-)1 yr(-)1, respectively). These low carbon sequestration values suggest that an in-depth analysis at the global scale is required to assess EW efficacy for carbon sequestration.