Water-soluble chitosan promotes remediation of Pb-contaminated soil by Hylotelephium spectabile

Water-soluble chitosan (WSC) has been studied for its ability to mobilize soil Pb and promote the phytoremediation by Hylotelephium spectabile in Pb-contaminated fields. We aimed to clarify the internal mechanism by which WSC impacts phytoremediation by examining plant growth and Pb accumulation performance of H. spectabile as well as the Pb form, functional groups, and mineral phases of Pb-contaminated soil. WSC effectively decreased soil pH and activated Pb migration in rhizosphere soils, with a considerable increase in water-soluble and acid-extractable Pb by 29%–102% and 9%–65%, respectively, and a clear decreasing trend in reducible and oxidizable Pb. Fouriertransform infrared spectroscopy revealed a significant increase in amino and hydroxyl groups in the soil generated by WSC. The coordination of Pb with amino and hydroxyl groups may play an important role in the formation of Pb complexes and activation of Pb in soil. In field trials, the application of WSC significantly increased Pb accumulation in H. spectabile by 125.44%, reaching 92 g/hm². Moreover, the organic matter and nitrogen in the soils were increased by WSC, which improved the growth conditions of H. spectabile. No obvious growth inhibition was observed in either the pot or field trials. Therefore, WSC is a promising chelating agent for mobilizing Pb in soil. Additionally, WSC can be potentially used to boost H. spectabil-mediated phytoremediation of Pb-contaminated farmland.