Combined toxicity of chloride-based and eco-friendly deicers with nanoplastics on Lemna minor and Salvinia natans

With the increasing frequency of heavy snow events projected under climate change, the use of deicers for winter road maintenance is expected to rise, leading to their discharge into freshwaters where they may co-occur with nanoplastics (NP). This study evaluated the combined toxicity of four deicers, sodium chloride (NaCl), calcium chloride (CaCl₂), a NaCl-CaCl₂ mixture, and the eco-friendly calcium magnesium acetate (CMA) with polystyrene NP to the aquatic plants Lemna minor and Salvinia natans. Endpoints included growth inhibition, root cell viability, and photosynthetic performance. Co-exposure outcomes were deicer-specific and generally increased with NP concentration; however, interaction analysis indicated no clear synergistic toxicity. Notably, CMA produced lower EC₅₀ values than the chloride salts and elicited a distinct response pattern, potentially related to oxygen demand during CMA degradation. Species-specific physiological differences were also observed between L. minor and S. natans. These results indicate that nanoplastics can modify deicer toxicity and that both traditional and eco-friendly deicers may pose ecological risks, underscoring the need for careful regulation and evaluation of alternative deicing agents.