Terrestrial enhanced weathering is the spreading of silicate powder on land, and can sequester atmospheric CO₂ through carbonation of calcium- and magnesium-rich minerals. When applied to soils, at suitable geochemical conditions, alkaline minerals lead to accumulation of soil inorganic carbon as pedogenic carbonates. Agricultural land covers 37 % of the Earth’s land surface, thus offering a natural sink for atmospheric CO₂. Wollastonite (CaSiO₃) has been commercialized in Ontario as an agricultural soil amendment for several years, but it is not known if or how much CO₂ is sequestered annually. In the present study, wollastonite-amended soils were collected from three commercial-scale fields located in Ontario: a leafy vegetables farm in the town of Paris (Field 1); a potato farm in the settlement of Alliston (Field 2); and a soybean farm in the city of Woodstock (Field 3). Chemical and mineralogical assessments of these soils were conducted to determine their carbonate content and the fate of the wollastonite. The soil inorganic carbon (SIC) content was higher in all soils that had been amended with wollastonite, compared to controls, and in Field 1 the SIC content was 2.6 times higher in soil amended thrice with wollastonite compared to a single application. Mineralogical analysis showed the presence of additional polymorphs of SiO₂, which may originate from the wollastonite after the dissolution of calcium. This work provides further evidence, here for the first time at a regional scale, that soil amendment with alkaline silicates can be an effective geoengineering tool for climate change mitigation.

陆地增强型风化是硅酸盐粉末在陆地上的扩散，并且可以通过富含钙和镁的矿物质的碳化来隔离大气中的CO ₂。当在适当的地球化学条件下施用到土壤中时，碱性矿物会导致土壤无机碳以成岩碳酸盐的形式积累。农业用地占地球陆地表面的37％，因此为大气中的CO ₂提供了天然的汇。硅灰石（CaSiO ₃）作为农业土壤改良剂已在安大略省商业化了几年，但尚不知道是否或有多少CO ₂每年被隔离。在本研究中，从位于安大略省的三个商业规模的田地中收集了硅灰石改良过的土壤：位于巴黎镇的一个绿叶蔬菜农场（田地1）；阿里斯顿定居点的一个马铃薯农场（田野2）；和伍德斯托克市的一个大豆农场（田野3）。对这些土壤进行了化学和矿物学评估，以确定它们的碳酸盐含量和硅灰石的命运。与对照相比，用硅灰石改良的所有土壤的土壤无机碳（SIC）含量均高于对照，在田间1中，用硅灰石改良的三次土壤的SIC含量是单次施用的2.6倍。矿物学分析表明存在SiO ₂的其他多晶型物，可能是钙溶解后产生的硅灰石。这项工作首次在区域范围内提供了进一步的证据，表明使用碱性硅酸盐对土壤进行改良可以成为缓解气候变化的有效地球工程工具。