Combined Effects of Biochar-Sedum plumbizincicola on Cadmium Concentration in Cd-Contaminated Limestone Soil and Cadmium Absorption in Lactuca sativa

This study aimed to explore the possibility of "repairing while producing" Cd-contaminated limestone soil and to investigate the combined effect of biochar-Sedum plumbizincicola. A pot experiment was conducted to examine the effect of Cd-contaminated limestone soil remediation and Cd absorption by Lactuca sativa. Six treatments were examined: monocropping of Lactuca sativa and intercropping of Lactuca sativa with Sedum plumbizincicola in Cd-contaminated limestone soil with 0, 4%, and 10% biochar addition. The results showed that under the same biochar treatment, the biomass accumulation of Lactuca sativa under monoculture was 14.41%, 18.18%, and 42.83% higher than that under intercropping, respectively, but the differences were not significant; when 4% biochar was added, the concentration of Cd in the soil was significantly reduced. When 4% and 10% biochar were added, the Cd concentration under monoculture decreased by 45.42% and 158.75%, respectively, while the Cd concentration under intercropping decreased by 82.06% and 185.10%, respectively; the concentration of soil total Cd under intercropping was lower than that under monoculture, decreasing by 8.78%, 17.17%, and 36.61%, respectively. Biochar combined with Sedum plumbizincicola is a feasible strategy that can not only effectively reduce the concentration of Cd in Lactuca sativa but also enable the remediation of Cd-polluted soil.