Typical Tire Additives\nin River Water: Leaching, Transformation,\nand Environmental Risk Assessment

Tire wear particles (TWPs) released during vehicle driving\ncan\nenter water bodies, leading to leaching of tire additives (TAs) in\naquatic environments. However, the transformation behavior and related\necological impacts of TAs and their transformation products (TPs)\nremain unclear. In this study, laboratory-based simulation experiments\nand field investigations were conducted to explore the transformation\nmechanisms and ecological risks of TAs. After being placed in river\nwater for 24 h, about 7–95% of 12 investigated TAs in TWPs\nwere leached. Forty-eight TPs from eight TAs were tentatively identified\nalong with different transformation pathways via suspect screening\nby high-resolution mass spectrometry. Semiquantitative results indicated\nthat TPs derived from <i>N</i>-(1,3-dimethylbutyl)-<i>N</i>′-phenyl-<i>p</i>-phenylene-diamine (6PPD)\nwere predominant in leachates, while aryl hydrolysis and quinone pathways\nwere the main transformation pathways. Field investigations on urban\nsurface water samples from 16 sites in Hong Kong revealed the occurrence\nof 17 TAs and 1 TP, with concentrations ranging from 13.9 to 2230\nng/L (median ± standard deviation: 226 ± 534 ng/L). Sixteen\nTPs from six TAs were additionally identified via suspect screening.\nIt is estimated that 6PPD-quinone and seven TAs could pose medium\nto high ecological risk, while <i>N</i>-(1,3-dimethylbutyl)-<i>N</i>′-phenyl-<i>p</i>-quinonediimine, a frequently\ndetected TP, was identified as a persistent-bioaccumulative-toxic\nsubstance.