Tracking pedogenic carbonate formation and migration in agricultural soils amended with crushed wollastonite ore- Evidence from field trials

Abstract

Abstract Considered as a well-known carbon sequestration method, terrestrial enhanced rock weathering involves the application of crushed silicate-bearing minerals to urban and agricultural soils. Once dissolved in the soil-water system, alkaline minerals adjust the pH in a range favorable for pedogenic carbonate formation and, hence, atmospheric carbon drawdown. As a fast-weathering Ca-rich mineral, wollastonite is recognized as one of the primary candidates for this process. Although previous studies proved the potential of wollastonite to sequester carbon in croplands, no study has investigated the fate of wollastonite over the vertical profile of soil. Furthermore, no studies have investigated changes in the elemental composition of soils due to wollastonite amendment on a field scale. The present study presents the results of a multi-year sampling collection from different layers (0–15, 15–30, and 30–60 cm) of agricultural soil amended with wollastonite in Woodstock, Ontario, Canada. The impact of initial soil pH on pedogenic carbonate formation was also investigated with the inclusion of two more field trials. The results denoted wollastonite addition increases the inorganic carbon pool of soil up to 6.60 t CO2/ha at higher (20 t/ha) wollastonite dosage. The elemental composition and mineralogy analyses were indicative of weathering occurrence in soil samples. This study indicates that carbonate formation is not limited to surficial layers, and deeper layers also need to be taken into account for estimating carbon capture due to ERW practice.