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.车辆行驶过程中产生的轮胎磨损颗粒（Tire wear particles, TWPs）可进入水体，进而导致轮胎添加剂（Tire additives, TAs）在水生环境中发生溶出。然而，目前关于轮胎添加剂及其转化产物（Transformation Products, TPs）的转化行为与相关生态影响仍不明确。本研究通过室内模拟实验与野外实地调查，探究了轮胎添加剂的转化机制与生态风险。将轮胎磨损颗粒置于河水中培养24小时后，所检测的12种轮胎添加剂中约有7%~95%发生了溶出。借助高分辨质谱可疑筛查技术，本研究从8种轮胎添加剂中初步鉴定出48种转化产物及其对应的多条转化路径。半定量分析结果显示，溶出液中以N-(1,3-二甲基丁基)-N′-苯基对苯二胺（6PPD）衍生的转化产物占主导，芳基水解与醌类转化路径为主要的转化途径。对香港16个点位的城市地表水样品开展的野外调查显示，样品中共检出17种轮胎添加剂与1种转化产物，浓度范围为13.9~2230 ng/L（中位数±标准差：226±534 ng/L）。此外，通过可疑筛查还从6种轮胎添加剂中鉴定出16种转化产物。据评估，6PPD醌与7种轮胎添加剂可能存在中至高生态风险；而频繁检出的转化产物N-(1,3-二甲基丁基)-N′-苯基对苯醌二亚胺被鉴定为持久性生物累积性有毒物质。