Mechanistic Insights into the Effects of Aged Polystyrene Nanoplastics on the Toxicity of Cadmium to Triticum Aestivum

The widespread concern over nanoplastics (NPs) has prompted extensive research into their environmental impact. Concurrently, the study examined the combined toxicity of PS NPs and cadmium (Cd) on wheat. As indicated by the results of in situ Micro-ATR/FTIR, the aging process of PS NPs (50 nm) led to an increase in carbonyl and hydroxyl groups on their surface, enhancing hydrophilicity and consequently, the adsorption capacity for Cd. The toxicity assessment, measured by the impact on wheat leaf and root biomass after 7 d culture, revealed that pristine PS NPs with concentrations of 0-5000 mg·kg⁻¹ had a negligible effect on Cd toxicity to wheat leaves. However, aged PS NPs significantly intensified the inhibitory effect on wheat root growth, particularly at low Cd concentrations (≤ 5.0 mg·kg⁻¹). This synergistic toxicity between aged PS NPs and Cd is suspected to stem from the increased bioaccumulation of Cd in wheat, likely facilitated by the aged NPs. Thus, the study shed light on the aging behavior of soil surface NPs and its implications for environmental risk assessment.