Effect of Microplastics on the Growth of Wheat Seedlings in Biochar Remediation of Cd‐Contaminated Soil

The widespread occurrence of microplastics (MPs) in soil and their coexistence with cadmium (Cd) represent an emerging environmental hazard. Biochar (BC) has been widely recognized as an effective soil amendment for Cd remediation; however, it remains unclear whether the presence of MPs influences the efficacy of BC in promoting plant growth in Cd‐contaminated soils. In this study, a pot experiment was conducted to examine the effects of biodegradable polylactic acid (PLA) and non‐biodegradable polyamide‐6 (PA6) microplastics on wheat ( Triticum aestivum ) seedlings grown in Cd‐contaminated soil (3 mg·kg −1 ) amended with wheat‐straw biochar. Both unaged and dry‐wet cycle‐aged MPs (PLAD and PA6D) were introduced at concentrations of 0.25%, 0.5%, and 1% (w/w). Compared to BC alone, the combined MPs‐BC treatments reduced seedling fresh weight by 6%–45%. The addition of MPs generally increased root length, whereas unaged MPs suppressed plant height. Cd accumulation in both shoots and roots peaked under the 1% BC‐PA6 treatment, while MPs overall impeded Cd translocation from roots to shoots. PLA reduced the remediation efficiency of BC, as reflected by elevated peroxidase (POD) and malondialdehyde (MDA) levels, indicating enhanced membrane lipid peroxidation. In contrast, PA6 decreased POD activity but increased superoxide dismutase (SOD) and catalase (CAT) activities; MDA content rose following ageing, although unaged PA6 maintained low MDA levels. These findings elucidate how MPs interact with biochar in Cd‐contaminated soil and affect wheat seedling growth and antioxidative responses, thereby providing a scientific basis for optimizing soil remediation strategies under complex pollution conditions.