Comparative Phytotoxicity of Leachates from Aircraft and Automobile Tire Wear Particles on Mung Bean (Vigna radiata L.) Seed Germination and Seedling Growth

Tire wear particles (TWPs) are a significant source of microplastics and chemical additives in the environment; however, differences in the toxicity of particles from different vehicle types remain unclear. This hydroponic study compared the phytotoxicity of leachates from aircraft- and automobile-derived TWPs on mung bean. Both leachates inhibited seed germination and seedling growth, with aircraft TWP leachates showing stronger effects, including greater germination delays and more pronounced reductions in shoot height, root length, and root surface area. Physiological analyses revealed that TWP leachates induced oxidative stress, characterized by significant suppression of superoxide dismutase (SOD) activity, compensatory increases in catalase (CAT) and peroxidase (POD) activities, and marked accumulation of malondialdehyde (MDA), indicating severe membrane lipid peroxidation. Chlorophyll content decreased in all groups, with greater reductions under aircraft leachates. Toxicological Priority Index (ToxPi) modeling identified zinc as the shared primary risk factor, while aircraft tire-specific additives (e.g., dicyclohexylamine, 1,2-dihydro-2,2,4-trimethylquinoline) constituted a distinct risk component linked to differentiated formulations. Aircraft TWP leachates thus exhibit stronger phytotoxicity through multiple pathways. These findings support refined environmental risk assessment and targeted control measures for aircraft TWPs.