Currently, tire wear particles (TWPs), a typical type of black microplastics (MPs), are frequently overlooked as the major source of MPs in aquatic environments. TWPs are widely distributed and exhibit complex environmental behaviors. However, how natural forces affect the aging and release behavior of TWPs at the nano(micro)scale remains inadequately explored. This study systematically investigated the aging behavior and mechanism of TWPs under the action of simulated natural light and high-temperature in both dry and wet environments, as well as the effect of aging treatment on the released leachate. The findings demonstrated that aging treatment significantly altered the physicochemical properties of TWPs, including chain scission and surface oxidation, and facilitated the release of heavy metals and organic additives in the meantime. In particular, the leaching concentration of Zn exhibited a positive linear relationship with exposure time. In the thermal-aging process, the oxidation of TWPs was primarily caused by superoxide anion (O2•−). During the photo-aging exposure, TWPs exhibited heightened electron-donating capacity, resulting in the formation of more O2•− and singlet oxygen (1O2) to attack TWPs. Moreover, the analysis of leachate produced under light and high-temperature conditions suggested that heavy metals exerted low ecological risks in water. Nonetheless, the photo-aging process enhanced the toxicity of released leachate to L929 cells, which could be attributed to highly toxic additive transformation products (such as HMMM-411 and 6PPD-Q) and more heavy metals. These findings shed light on the fate of TWPs and the ecological risks posed by aged TWPs in aquatic environments.

中文翻译：

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基于机制和毒性分析，深入了解加速衰老和释放黑色微塑料（轮胎磨损颗粒）的自然力量


目前，轮胎磨损颗粒 （TWP） 是一种典型的黑色微塑料 （MP） 类型，作为水生环境中 MP 的主要来源，经常被忽视。TWP 分布广泛，表现出复杂的环境行为。然而，自然力如何在纳米（微）尺度上影响 TWP 的老化和释放行为仍未得到充分探索。本研究系统研究了 TWPs 在模拟自然光和高温作用下干湿环境下的老化行为和机制，以及老化处理对释放的渗滤液的影响。研究结果表明，老化处理显著改变了 TWPs 的物理化学性质，包括断链和表面氧化，同时促进了重金属和有机添加剂的释放。特别是，Zn 的浸出浓度与曝光时间呈正线性关系。在热老化过程中，TWPs 的氧化主要由超氧阴离子 （O2•−） 引起。在光老化暴露期间，TWPs 表现出更高的电子供体能力，导致形成更多的 O2•- 和单线态氧 （1O2） 来攻击 TWP。此外，对在光照和高温条件下产生的渗滤液的分析表明，重金属对水中的生态风险较低。尽管如此，光老化过程增强了释放的渗滤液对 L929 细胞的毒性，这可能归因于剧毒的添加剂转化产物（如 HMMM-411 和 6PPD-Q）和更多的重金属。这些发现揭示了 TWP 的命运以及老化的 TWP 在水生环境中带来的生态风险。