THE DECREASE OF HEAVY METAL ACCUMULATION IN WHEAT: THE IMPACT OF BIOCHAR ON SOIL HUMUS COMPOSITION AND CADMIUM BIOAVAILABILITY

As a new type of adsorption material, biochar has become a hotspot in the environmental field such as soil remediation and enhancement of carbon storage. However, little attention has been given to relationship between the deceased heavy metal bioavailability and the changes in soil humus composition with biochar addition. In this experiment, a pot experiment was conducted to apply different proportions of biochar (0%, 0.5%, 1%, 2% and 5%) to cadmium (Cd) -contaminated soil, and the soil physical and chemical properties, humic components, available Cd and Cd concentration in wheat were determined. Results showed that soil pH and soil organic matter (SOM) was significantly increased and the DGT-Cd was significantly decreased under all biochar treatments, with 5% biochar addition had the greatest impact. The content of fulvic acid (FA) and humin (HM) in soil increased with the increase of biochar addition, while the content of humic acid (HA) showed a decrease trend with the application of biochar. The Cd concentration in wheat roots, stems and grains was significantly negatively correlated with soil pH, HM, SOM and FA content, but positively with soil available cadmium (DGT-Cd) and HA. The results demonstrated that biochar can effectively immobilize heavy metals, thereby increasing soil pH, changing the humus component, and reducing heavy metal bioavailability in contaminated soils.