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）是由轮胎在道路上的磨损释放出来的，是最丰富的微塑料污染物之一。 每年有超过100万公吨的TWP被冲入水道，对鱼类和其他水生生物造成破坏性影响。虽然阳光照射可能会分解从TWP中浸出的一些化合物，但一些化合物将持续存在于环境中，并且还会形成新的化合物和更具毒性的转化产物。许多渗入水中的TWP化合物尚不清楚，阳光对TWP化合物的浸出，毒性和命运的影响也仍然未知。该项目的目标是解决我们知识中的主要空白：1）从TWP中浸出的许多有机化合物，2）TWP衍生的化学品应根据其毒性优先进行进一步研究，以及3）阳光如何转化和降解水中的不同TWP化合物。研究小组将确定在阳光照射和黑暗条件下从不同轮胎类型的胎面颗粒中浸出的各种化合物，描述它们的毒性，并评估TWP化合物在模拟阳光下的持久性和衰变。该项目的成功完成将通过产生有关不同轮胎磨损颗粒毒性的基础知识而造福社会，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，包括指导圣地亚哥州立大学的两名研究生，将为社会带来额外的好处。轮胎磨损颗粒（TWP）在流域的积累已成为水生生态系统的主要威胁，水中的TWP与城市径流鱼类和大型无脊椎动物死亡综合征直接相关。鉴于某些轮胎配方中天然橡胶含量仅为20%，但含有大量合成聚合物、金属和添加剂，因此许多可能沥滤到水柱中的TWP衍生化合物和转化产物尚不清楚，其毒性尚未确定-特别是通过直接或间接光解形成的化合物。一些沥滤化合物和TWP的转化产物将具有耐光性，并在环境中持久存在，而其他化合物则会迅速衰减，并且逐个化合物确定沥滤和光化学降解的动力学是一项挑战。拟议研究的总体目标是评估控制有毒TWP衍生化合物和转化产物生产的基本过程。具体目标是：1）探测直接和间接光解对TWP中有毒微污染物的浸出、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）开发TWP衍生化合物衰变的动力学模型。实验将使用来自乘用汽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，并在不同的条件下进行，包括阳光和黑暗。这项研究的成功完成有可能通过对阳光在TWP衍生化合物的形成和破坏中的作用的机械理解产生变革性影响。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（梅萨）计划协调，领导高影响力的经验和推广活动，包括STEM阴影日，K-12学生的“雨水碎片捕获设备竞赛”，并通过梅萨暑期学院指导本科生。此外，PI计划通过CSU COAST计划网络向加州州决策者简要介绍研究结果。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

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.