From the proposed evolution processes of the anions, we find that the formation of these ions are closely related to the decomposition of biomass, and the higher degree of decomposition (higher pyrolysis temperature) will lead to the higher amounts of OH−, CO32−, and Si species presented on biochar surface. Some previous studies have also found this phenomenon. Yuan et al. reported that the pHs and carbonate contents of biochar derived from different straws increased with pyrolysis temperature56; Xiao et al. found that the dissolved Si species released from biochar prepared by rice straw increased33 when the temperature increased from 250 °C to 700 °C.