Synergistic effects of aged lignin-based biochar and selenium fertilization on heavy metal remediation in agricultural soils
Xianzhen Li, Yongchao Yu, Ruimei He, Qing Zhen, Diao She
Abstract
The widespread contamination of soils with heavy metals, such as cadmium (Cd) and zinc (Zn), presents significant threats to agricultural productivity and environmental health. Biochar (BC) and selenium (Se) have significant potential to alleviate soil heavy metal contamination and ensure crop safety. However, the current understanding of the property changes in aged lignin-based biochar and its interaction with Se in enhancing plant resistance remains limited. This study investigates the potential of aged lignin-based biochar (LBC) and foliar-applied selenium (Se) to mitigate heavy metal contamination and enhance pakchoi growth in soils contaminated with cadmium (Cd) and zinc (Zn). Results indicate that aging of LBC facilitated the formation of C–O and Si–O groups, with mineral components transitioning from MgO and Mg 2 SiO 4 to stable forms of SiO 2 and Ca, MgCO 3 . Additionally, during the adsorption of Cd 2+ and Zn 2+ , the contribution of minerals decreased, while that of non-mineral components increased, with a shift from the Freundlich to the Langmuir adsorption model. Furthermore, the synergistic effect of aged LBC with foliar Se significantly enhanced pakchoi' s photosynthesis and antioxidant enzyme activity of pakchoi , isolatied Cd 2+ and Zn 2+ in vacuoles and cell walls, and effectively reduced the uptake of these metals and mitigating their toxicity. This research offers novel insights into the synergistic effects of aged LBC and Se on heavy metal remediation in agricultural soils, offering a sustainable strategy to improving food safety and soil health. • Mineral components transitioned from MgO and Mg 2 SiO 4 to stable SiO 2 and Ca,MgCO 3 . • During Cd 2 + and Zn 2 + adsorption, non-mineral mechanism contribution roles increased. • Aged BC and Se increased photosynthetic and CAT, SOD activities in pakchoi. • Aging BC and Se increased Cd and Zn in cell wall by 87.9 % and 84.4 %, respectively. • Interactions among Si, Mg, and Se contribute to the synergistic effect of BC and Se.