Effects of microplastics in soil on the regulation of cadmium bioavailability by biochar

Given the widespread and persistent presence of microplastics (MPs) in soil, their coexistence with cadmium (Cd) poses significant environmental risks. Biochar (BC) serves as an economically viable and environmentally sustainable amendment for soil remediation. However, the existing research on BC application in Cd-contaminated soil has yet to adequately consider the influences of the presence of MPs. Therefore, based on the analysis of Cd sorption characteristics on BC and MPs, the soil incubation and pot experiments were conducted in Cd-contaminated soil to elucidate the effects of polyethylene MPs and corn straw BC on Cd availability and accumulation in Chinese cabbage. After 60 days of incubation, the application of BC led to a considerable decline in the available Cd contents in the soil, with decreases of 47.3% and 42.4% for DTPA-Cd and acid-soluble Cd respectively, while the presence of MPs partially weakened the immobilization effect of BC on Cd. The BC promoted plant growth, but the combined presence of MPs and BC inhibited it, which was attributed to the adverse effects of MPs. Compared with the sole BC application, the BC-MPs treatment hindered the accumulation of Cd from the contaminated soil to the plant. The results of this study provide a certain theoretical basis for the remediation ability of BC for MPs-Cd co-contaminated soils.