Tire tread particles are microplastics (< 5 mm) and leach organic chemicals into aquatic environments. It is important to understand the behavior of tire wear compounds in sunlight-exposed waters in terms of their persistence, removal, and transformation. Therefore, we conducted photolysis experiments with leachates from laboratory-generated tire tread particles (TTP) over 72 h in a solar simulator to evaluate the behavior of leached compounds and fluorescent components over time. Compared to initial leachates, simulated sunlight exposure resulted in ∼12% decrease in dissolved organic carbon, 11% reduction in the total fluorescence of leachates, and ∼30% removal of the 213 chromatographic features detected by nontargeted analysis (NTA) using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. A decrease in total chemical abundance determined by NTA was also observed, with normalized peak areas decreasing from 19.8 at 0 h to 12.6 in the 72 h photoirradiated samples and to 17.1 in the dark samples. Fifty-three compounds were tentatively identifiable based on mass spectral matching and among them, 12 compounds were confirmed with authentic standards. Among the 53 compounds, 19 compounds were photo-labile, 27 were photo-resistant, and 7 were photo-transformation products. NTA also identified compounds previously unreported as tire-related compounds. Parallel factor analysis (PARAFAC) modeling of three-dimensional excitation-emission-matrix (EEM) data identified five fluorescent components. PARAFAC component C4 (excitation/emission peak at 285/445 nm) was found to be a fluorescent analog for 6PPD. Rapid double exponential decay kinetics were observed for the 6PPD-like component during photoirradiation. Similarly, the peak fluorescence of commercially available 6PPD exposed to simulated sunlight was reduced by >90% in the first 0.5 h of photoirradiation. 6PPD photodegradation resulted in the production of a fluorescent transformation product resembling PARAFAC Component C2 (with emission at 360 nm). These results prove that EEM fluorescence analyses can serve as a rapid method for kinetics analysis of 6PPD, and may be combined with NTA compound tentative identification to track the behavior of other TTP-derived compounds in experimental studies.

中文翻译：

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模拟阳光照射下轮胎胎面颗粒浸出的化合物的行为


轮胎胎面颗粒是微塑料（< 5 mm），会把有机化学物质浸入水生环境中。了解轮胎耐磨化合物在阳光照射下的水中的行为，包括其持久性、去除和转化性，这一点很重要。因此，我们在太阳模拟器中用实验室生成的轮胎胎面颗粒 （TTP） 中的渗滤液进行了 72 小时的光解实验，以评估浸出化合物和荧光成分随时间的行为。与初始渗滤液相比，模拟阳光照射导致溶解有机碳减少约 12%，渗滤液总荧光减少 11%，并使用综合二维气相色谱与飞行时间质谱联用非靶向分析 （NTA） 检测到的 213 种色谱特征去除约 30%。还观察到 NTA 测定的总化学丰度降低，归一化峰面积从 0 h 的 19.8 下降到 72 h 光照射样品中的 12.6，在深色样品中下降到 17.1。基于质谱匹配初步鉴定出 53 种化合物，其中 12 种化合物被真实标准品确认。在 53 个化合物中，19 个化合物为光不稳定型，27 个为光抗性，7 个为光转化产物。NTA 还确定了以前未报道的轮胎相关化合物。三维激发-发射-矩阵 （EEM） 数据的平行因子分析 （PARAFAC） 建模确定了 5 种荧光成分。发现 PARAFAC 组分 C4 （285/445 nm 处的激发/发射峰） 是 6PPD 的荧光类似物。在光照射过程中观察到 6PPD 样成分的快速双指数衰减动力学。 同样，在光照射的前 3 小时内，暴露于模拟阳光下的市售 6PPD 的峰值荧光降低了 >90%。6PPD 光降解导致产生类似于 PARAFAC 组分 C2 的荧光转化产物（发射波长为 360 nm）。这些结果证明，EEM 荧光分析可以作为 6PPD 动力学分析的快速方法，并且可以与 NTA 化合物试探性鉴定相结合，以跟踪实验研究中其他 TTP 衍生化合物的行为。