Implications of the Riverine Response to Enhanced Weathering for CO2 removal in the UK

Enhanced silicate weathering, the application of crushed calcium and magnesium-rich rocks to arable cropland, has been proposed as a potential negative emissions technology for drawdown atmospheric CO2. Previous estimates have suggested that enhanced weathering (EW) remove significant quantities CO2, much 6–30 Mt CO2 yr−1 UK. However, if secondary carbonates are precipitated during riverine transport products EW, portion this will be re-released, lowering net carbon dioxide removal (CDR) mitigation strategy. Here, we assess fluvial response EW in UK by calculating expected carbonate precipitation due dissolution 10–50 t ha−1 rock on available cropland major catchments. Increases calcite saturation export soluble cations sourced from soil rivers simulated cross thresholds spontaneous several river catchments (e.g. Great Ouse, Thames). Catchments most susceptible those with high ratio water discharge. On average, is make 16% (10 ha−1), 21% (20 ha−1) or 27% (50 less effective at removing than predicted absence such precipitation. Furthermore, when placing strict silica limitations reactions within soils, CDR reduced considerably, 0.23 yr−1. Although reducing suggest under rapid conditions, prevent pH increases over safe level freshwater ecosystems (pH > 9). Together, simulations ambient hydrological conditions may certain agricultural areas call methods quantify treatments further investigate role suppressing reactions.