Adsorption Behaviors of Cadmium Regulated by Microplastics Properties in a Forest Soil

Co-contamination of microplastics (MPs) and cadmium (Cd) has attracted attentions in forest soils due to their complex behaviors and ecological risks. This study investigates the interactions between MPs and Cd²⁺, focusing on effects of different types (polyethylene: PE, polybutylene succinate: PBS, poly-11-bromoundecyl acrylate: PBA), sizes (75-150 and 150-300 μm) and concentrations (1% and 10%) of MPs on soil properties. Results showed that MPs significantly influence contents of soil dissolved organic carbon and available nitrogen, while increased MPs concentrations reduced the dissolved organic matter (DOM) availability and decomposition. Adsorption and desorption of Cd²⁺ were higher in biodegradable MPs (PBS and PBA), with the Freundlich model providing a better fit for Cd²⁺ adsorption. Pearson correlation and redundancy analysis identified soil DOM, number of humic-like substances, and microbial by-products as key factors influencing Cd²⁺ behavior. These findings contribute to understanding risks of co-contamination by MPs and heavy metals in forest soils.