Mn-modified bamboo biochar improves soil quality and immobilizes heavy metals in contaminated soils

Soil contamination by heavy metals is becoming increasingly serious and needs to be solved urgently. Modified biochar is an effective strategy to solve this problem, and previous studies have only focused on the remediation of single heavy metal contaminated soils through biochar. However, the effects of metal-modified bamboo biochar on soil improvement and the passivation of heavy metals are still unknown. In this study, the Mn-modified bamboo biochar was prepared and the effects of Mn-modified bamboo biochar on soil improvement and the passivation of heavy metals were investigated. The results showed that Mn-modified bamboo biochar can improve the physical and chemical properties of soil, and immobilize heavy metals (i.e., Pb, As, Cd, and Cu). After adding Mn-modified bamboo biochar, soil pH decreased by 0.08-0.70, organic matter content increased by 8.00-45.13%, and alkaline hydrolysis nitrogen content increased by 1.84-5.78%. The diethylene triamine penta-acetic acid (DTPA)-extractable Pb, As, Cd, and Cu decreased by 21.25-58.65%, 7.76- 34.02%, 36.44-46.50%, and 3.13-35.21%, respectively, while the acid-extractable Pb, As, Cd, and Cu decreased by 27.81-43.31%, 23.91-26.01%, 17.56-50.60%, and 7.94-18.09% respectively. These results indicated that Mn-modified bamboo biochar can improve the physicochemical properties of the soil and effectively inactivate multi-heavy metals in contaminated soil, Mn-modified bamboo biochar is a potential alternative agent for the management of multi-heavy metal contaminated soils.