摘要：The heavy metal sorption capacity of biochar prepared directly from biomass feedstock was relatively low, and method to improve its performance in adsorption and stability is needed. A pot experiment was conducted to investigate the effect of chi- tosan-modified biochar on plant growth, Cu, Cd uptake, and chemical and microbial characteristics of the rhizosphere of lettuce. Rhizosphere soil samples were analyzed for pH, concentrations of available Cu, Cd measured by diffusive gradients in thin-films (DGT) and microbial biomass carbon and nitrogen. The results showed that compared with the unmodified biochar, the application of chitosan-modified biochar significantly promoted plant biomass and decreased Cu, Cd uptake by plants with increased soil pH, decreased DGT measured Cu and Cd concentrations and increased microbial biomass carbon and nitrogen in the rhizosphere. When the application amount of chitosan-modified biochar was 5%, Cu and Cd concentrations in the shoots were decreased by 43% and 62.49% respectively, while decreased by 57.29% and 58.7% in the roots respectively. Meanwhile, the pH was increased by 0.15 units, and content of available Cu and Cd measured by DGT decreased by 67.95% and 64.29%, respectively, while the microbial biomass carbon and nitrogen were increased by 44.18% and 57.85%, respectively. Therefore, it was speculated that increased soil pH and decreased soil available Cd and Cu contents may be the main mechanism for chitosan-modified biochar to reduce Cd and Cu contents in lettuce. Chitosan-modified biochar can be used as a practical alternative soil amendment to inhibit the absorption of heavy metals by vegetables in contaminated soils and improve soil nutrient status.
