Accelerated weathering of silicate rock dusts

Five commercial RDs were tested in four acid forest soils. First, RD dissolution was measured in batch renewal systems during one year at various starting pH (3.5-5.5) and constant temperatures (20-65°C). These showed that the ANCs of RDs exhibit a fast fraction (half-life <1 day) followed by a slower fraction. Second, pHstat tests performed between pH 3.5 and 4.5 revealed surface normalised dissolution rates that decreased factors 10-100 per unit pH increase, the range depending on the RD. The ranking of the observed surface area normalised dissolution confirmed that of literature-based values, weighed by the XRD derived mineralogical fractions. Third, lime-calibrated agitated soil-RD suspension tests were conducted during two months and yielded ANCs that were factor 2-5 times larger than in the batch renewal test because of buffering effects of soil particulates. Finally, an outdoor soil mesocosm on the four acid soils amended with RDs at 12 Mg/ha and 340 Mg/ha was established and soil pH was monitored during 2 years.

本研究选取5种商用RD，在4种酸性森林土壤中开展试验。首先，在分批更新体系中，于不同起始pH（3.5~5.5）、恒定温度（20~65℃）条件下开展为期1年的RD溶解性能测试，结果表明RD的酸中和容量（Acid Neutralizing Capacity, ANC）呈现双相溶解特征：先为快溶组分（半衰期<1天），随后为慢溶组分。其次，在pH 3.5~4.5范围内开展pH稳态试验（pH-stat），结果显示表面归一化溶解速率随pH每升高1个单位下降10~100倍，具体降幅范围因RD种类而异；经X射线衍射（X-ray Diffraction, XRD）得到的矿物组分占比加权后，观测得到的比表面积归一化溶解速率排序与文献报道值一致。第三，开展为期2个月的经石灰校准的搅拌式土壤-RD悬浮液试验，由于土壤颗粒的缓冲效应，测得的ANC较分批更新体系试验高出2~5倍。最后，针对上述4种酸性森林土壤，分别以12 Mg/公顷和340 Mg/公顷的用量施加RD，构建室外土壤中宇宙试验体系，并连续2年监测土壤pH变化。