Quantification of CO2 uptake by enhanced weathering of silicate minerals applied to acidic soils
Christiana Dietzen, Minik T. Rosing
Abstract
The application of ground silicate minerals to agricultural soils has been proposed as a method for taking up CO2 by enhancing the weathering rate of these minerals through their exposure to soil acids. Alternatively, glacial rock flour, a finely grained material which is abundantly available without the need for energy-intensive grinding, could be used. However, simple and inexpensive methods for determining the amount of CO2 taken up as a result of weathering of applied minerals are still needed, and the impact of non-carbonic acids on CO2 uptake has yet to be accounted for. Here, we present a protocol for correcting estimates of CO2 uptake due to enhanced mineral weathering to account for weathering by non-carbonic soil acids. We determine that soils with a pH below 6.3 need correction for weathering by other acids than carbonic acid and that, given the impact of non-carbonic acids, soils with a pH below 5.2 may not be ideal candidates for mineral applications aimed at CO2 uptake, depending on the pCO2. We report an estimated CO2 uptake of 728 kg CO2 ha−1 after the application of 50 tons ha−1 of Greenlandic glacial rock flour to an acidic, sandy soil in Denmark over 3 years.