Effect of coal-gangue derived calcium silicate hydrate on the growth of pakchoi in copper contaminated soil

<b>ABSTRACT</b>This study investigated the effect of calcium silicate hydrate (C-S-H) on copper (Cu) uptake, availability, geochemical speciation, and immobilization in the soil-plant system. C-S-H, prepared from coal gangue, was added to Cu-contaminated soil to assess its effect on pakchoi growth. C-S-H application increased soil pH, organic matter content, and cation exchange capacity while reducing electrical conductivity. It also increased soil microbial biomass and enzyme activities while reducing Cu bioavailability, mobility, and leaching toxicity. The possible Cu fixation mechanisms by C-S-H in soil media included ion exchange, complexation, and precipitation. Moreover, fresh biomass, dry biomass, plant height, and root length increased significantly by 5.81-23.74%, 8.48-34.69%, 5.13-29.42%, and 6.78-28.81%, respectively. Cu content in the shoots and roots of pakchoi decreased by 17.30-66.04% and 11.77-58.09%, respectively. These findings demonstrate that C-S-H is an effective soil amendment for reducing Cu accumulation in the pakchoi and enhances Cu solidification ability in contaminated soil.