Effect of Biochar-Based Organic Fertilizers on the Transport and Accumulation of Heavy Metals in Soil and Plants

Abstract

Anaerobically digested digestate is mostly used as organic fertilizer, but there is still a potential risk of heavy metal pollution. Biochar and bio-organic fertilizer through passivation can effectively reduce the mobility of heavy metal ions in soil, with the strong adsorption capacity of heavy metals, and are widely used in soil remediation. In this study, digestate as raw material supplemented with biochar was applied to simulated heavy metal-contaminated soil, and its effects on heavy metal content and the transformation of forms in soil and crop systems were systematically investigated. The application of biochar-based organic fertilizer to simulated heavy metal-contaminated soils resulted in large differences in the morphological distribution of heavy metals, which was reflected in a significant decrease in the content of heavy metals in the weakly acid-extractable state and an increase in the content of heavy metals in the residue state, and promoted the transformation of soil heavy metals from the weakly acid-extractable state to the residue state. There were differences in the accumulation of heavy metals in the above ground and below ground parts of cabbage, and Cu, Zn, Cd, and Pb were mainly accumulated in the below ground parts of the plants. The present study offers an effective methodology for the remediation of soil and plant contamination by a range of heavy metals (Cu, Zn, Cd, and Pb), from the weak acid extraction stage to the residue stage. This approach is of particular significance for the advancement of sustainable agriculture and environmental remediation.