Typical Tire Additives in River Water: Leaching, Transformation, and Environmental Risk Assessment

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