Chemical Dynamics of Organic Peroxy Radicals at Aerosol Particle Interface

该奖项由美国国家科学基金会化学部环境化学科学项目颁发，支持加州大学河滨分校张浩飞教授研究有机气溶胶（OA）颗粒。大气OA对地球气候的影响至关重要，但人们对其了解甚少。不确定性主要是由于复杂的化学过程，在其数周的生命周期中不断改变OA成分。张教授和他的团队研究了有机过氧自由基（RO2）在颗粒表面的化学反应。这些化学过程在很大程度上决定了颗粒界面的化学组成和理化性质。更好地了解这些反应的细节可以提高我们对OA的演变和影响的理解。该项目的其他更广泛的影响包括对本科生和研究生的培训和指导，特别是那些来自代表性不足群体的学生。此外，张教授还与河滨高中合作，为少数民族学生提供服务，并参加了一个旨在加强不同学生STEM教育的暑期学院项目。本项目重点研究OA代用物的非均相羟基自由基氧化及RO2在OA粒子界面的后续途径。这包括以前未被开发的RO2 +羟基自由基，RO2 +一氧化氮，RO2二聚化和RO2自氧化反应。实验室氧化实验使用混合连续流反应系统进行。这提供了各种RO2反应途径的相对重要性的信息。不同的氧化途径受OA组成、液态水含量、氧化时间尺度和氧化剂浓度的影响。该团队使用一套先进的质谱仪器系统地研究氧化动力学和关键氧化产物的化学成分。一个多相反应-扩散动力学模型框架代表感兴趣的界面RO2过程正在开发。该模型基于实验结果，对目前对自由基引发的OA非均相氧化机制的理解进行了重要的扩展。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

This award from the Environmental Chemical Sciences Program in the NSF Division of Chemistry supports Professor Haofei Zhang at the University of California, Riverside to study organic aerosol (OA) particles. Atmospheric OA affect the Earth’s climate in crucial but poorly understood ways. The uncertainty is largely due to the complex chemical processes that constantly change OA compositions during their lifetime of weeks. Professor Zhang and his group study the chemical reactions of organic peroxy radicals (RO2) at the surfaces of the particles. These chemical processes largely determine the chemical composition and physiochemical properties of the particle interface. Better knowledge of the details of these reactions improves our understanding of the evolution and impacts of OA. Other broader impacts of this project include the training and mentoring of undergraduate and graduate students, especially those from the underrepresented groups. In addition, Professor Zhang leads outreach activities with Riverside high schools that serve minority students and participates in a summer academy program aimed at enhancing STEM education for diverse students.The project focuses on the heterogeneous hydroxyl radical oxidation of OA proxies and the subsequent pathways of RO2 at the OA particle interface. This includes the previously under-explored RO2 + hydroperoxyl radical, RO2 + nitric oxide, RO2 dimerization, and RO2 autoxidation reactions. Laboratory oxidation experiments are performed using a hybrid continuous-flow reaction system. This provides information on the relative importance of the various RO2 reaction pathways. The different pathways are impacted by the OA composition, liquid water content, oxidation timescales, and oxidant concentrations. The team uses a suite of advanced mass spectrometry instrumentation to systematically study the oxidation kinetics and the chemical composition of key oxidation products. A multiphase reaction-diffusion kinetic model framework representing the interfacial RO2 processes of interest is being developed. The model is based on experimental results and presents a crucial extension to the current understanding of radical-initiated OA heterogeneous oxidation mechanisms.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.