Sunlight and tire wear particles - a toxic combination? Evaluating mechanisms for mobilization and degradation of tire particle compounds

轮胎磨损颗粒(TWP)是轮胎在道路上磨损时释放出来的，是微塑性污染物中含量最丰富的形式之一。每年有100多万公吨TWP被冲进水道，对鱼类和其他水生生物造成毁灭性影响。虽然阳光暴晒可能会分解从TWP中浸出的一些化合物，但一些化合物会留在环境中，新的化合物和更多有毒的转化产物也会形成。许多浸出到水中的TWP化合物尚不清楚，阳光对TWP化合物浸出、毒性和命运的影响也仍然未知。这个项目的目标是解决我们在以下方面的主要知识空白：1)从TWP中浸出的许多有机化合物；2)根据TWP的毒性，优先研究哪些TWP衍生化学品；以及3)阳光如何转化和降解水中不同的TWP化合物。研究小组将确定不同类型轮胎的胎面颗粒在阳光照射和黑暗条件下淋洗出的各种化合物，描述它们的毒性，并评估TWP化合物在模拟阳光存在下的持久性和衰减性。该项目的成功完成将通过产生关于不同轮胎磨损颗粒的毒性的基本知识来造福社会，这些知识可以为未来与轮胎制造、轮胎回收和雨水质量绿色基础设施相关的立法提供信息。通过学生教育和培训将获得更多的社会利益，包括对圣地亚哥州立大学的两名研究生进行指导。集水区轮胎磨损颗粒(TWP)的积累已成为对水生态系统的主要威胁，水中的TWP与鱼类和大型无脊椎动物的城市径流死亡综合症直接相关。鉴于一些轮胎配方含有低至20%的天然橡胶，但含有大量的合成聚合物、金属和添加剂，因此许多可能被浸出到水柱中的TWP衍生化合物和转化产品尚不清楚，其毒性也尚未确定--特别是通过直接或间接光解形成的化合物。从TWP中浸出的一些化合物和转化产物将具有耐光性并持续存在于环境中，而另一些则会迅速腐烂，因此逐个化合物地确定淋溶和光化学降解的动力学是一个挑战。拟议研究的首要目标是评估控制有毒雷公藤多酚衍生化合物和转化产品生产的基本过程。其具体目标是：1)探索直接和间接光解对TWP中有毒微污染物的淋溶、转化和持久性的影响；2)阐明活性中间体在这些过程中的作用；3)建立TWP衍生化合物的衰减动力学模型。实验将使用乘用车和高性能轮胎的各种样品进行，这些样品具有不同的化学成分，在不同的条件下，在阳光和黑暗中。这项研究的成功完成有可能通过从机理上理解阳光在雷公藤衍生化合物的形成和破坏中的作用而产生变革性的影响。为了实现该项目的教育和培训目标，研究生将与数学工程和科学成就(MESA)计划协调，领导高影响力的体验和外联活动，包括STEM阴影日，为K-12学生举办的“雨水碎片捕获装置大赛”，以及通过MESA暑期学院指导本科生。此外，PIS计划通过CSU海岸计划网络向加利福尼亚州的政策制定者介绍研究结果。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Tire wear particles (TWP) are released from abrasion of tires on roadways and are one of the most abundant forms of microplastic pollutants. More than one million metric tons of TWP are flushed into waterways each year, with devastating impacts for fish and other aquatic organisms. While sunlight exposure may break down some of the compounds leached from TWP, some compounds will persist in the environment, and new compounds and more toxic transformation products also will form. Many of the TWP compounds that leach into water are not yet known, and the effects of sunlight on TWP compound leaching, toxicity, and fate also remain unknown. The goal of this project is to address major gaps in our knowledge of 1) the many organic compounds that leach from TWP, 2) which TWP-derived chemicals should be prioritized for further study based on their toxicity, and 3) how sunlight transforms and degrades different TWP compounds in water. The research team will identify the diverse compounds leached from tread particles from different tire types under solar exposure and dark conditions, describe their toxicity, and evaluate the persistence and decay of TWP compounds in the presence of simulated sunlight. The successful completion of this project will benefit society through the generation of fundamental knowledge about the toxicity of different tire wear particles which could inform future legislation related to tire manufacture, tire recycling, and green infrastructure for stormwater quality. Additional benefits to society will be achieved through student education and training including the mentoring of two graduate students at San Diego State University.The accumulation of tire wear particles (TWP) in watersheds has emerged as major threat for aquatic ecosystems, with TWPs in water being linked directly to urban runoff mortality syndrome for fish and macroinvertebrates. Given that some tire formulations contain as little as 20% natural rubber but have a vast array of synthetic polymers, metals, and additives, many of the TWP-derived compounds and transformation products that may be leached into the water column are not yet known and their toxicity has not been established - especially the ones that form via direct or indirect photolysis. Some leached compounds and transformation products from TWP will be photo-resistant and persist in the environment while others will decay rapidly, and determining the kinetics of leaching and photochemical degradation on a compound-by-compound basis is a challenge. The overarching goal of the proposed research is to evaluate the fundamental processes that control the production of toxic TWP-derived compounds and transformation products. The specific objectives are to 1) probe the effects of both direct and indirect photolysis on leaching, transformation, and persistence of toxic micropollutants from TWPs, 2) elucidate the role of reactive intermediates in these processes, and 3) develop kinetic models for decay of TWP-derived compounds. Experiments will be performed using a variety of samples from passenger cars and high-performance tires, which have different chemical compositions and in different conditions, sunlight and dark. The successful completion of this research has the potential for transformative impact through the mechanistic understanding of the role of sunlight in the formation and destruction of TWP-derived compounds. To implement the education and training goals of the project, graduate students will lead high impact experiences and outreach activities in coordination with the Math Engineering and Science Achievement (MESA) program, including STEM Shadow Day, the “Stormwater Debris Capture Device Competition” for K-12 students, and mentoring undergraduates through the MESA Summer Academy. In addition, the PIs plan to brief California State policymakers on research findings through the CSU COAST Program network.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.