Interactions between Organic Oxidation and Acid-base Chemistry during Particle Formation and Growth

这个项目涉及研究大气中新粒子的形成和生长。这项工作包括设计和参与实验，作为欧洲核子研究中心宇宙离开室外液滴（CLOUD）联盟的一部分，并参与卡内基梅隆大学（CMU）的补充实验。通过提高对新粒子形成机制的理解，该项目解决了与气候变化和空气质量相关的重要国家和国际利益。这项工作将研究涉及硝酸、硫酸、氨和胺的新颗粒形成，以及萜烯和芳香前体的高氧有机化合物形成的颗粒。实验试图回答以下问题：(1)不同体系（即α蒎烯- RO2 +异戊二烯- RO2→ROOR+O2）的自氧化反应和过氧自由基“二聚化”反应的温度依赖性如何结合起来控制“纯有机”体系中颗粒的形成和生长？(2)氧化有机体系和酸碱体系在颗粒形成和生长过程中是协同作用还是独立作用，还是相互“破坏”并抑制成核？这两个相互关联的项目将专注于酸、碱和高度氧化（和极性）有机物之间的相互作用，范围从颗粒形成本身到生长到5-10纳米。关键问题是确定硝酸是直接参与颗粒形成还是激活形成颗粒的生长，以及酸碱和有机颗粒形成途径是在大气中独立进行还是协同或拮抗相互作用。包括测量的形成和生长速率，气相蒸汽测量和颗粒组成在内的可观测数据将结合起来紧密地约束这些耦合系统。在CLOUD， CMU团队将使用碘化物化学电离质谱仪来测量气体和生长颗粒的组成，后者由聚四氟乙烯过滤器（FIGAERO CIMS）热解吸。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 project involves the investigation of the formation and growth of new particles in the atmosphere. The effort includes the design and participation of experiments as part of the Cosmics Leaving Outdoor Droplets (CLOUD) consortium at CERN and participation in complementary experiments at Carnegie Mellon University (CMU). By improving the understanding of mechanisms for new particle formation, this project addresses vital national and international interests associated with climate change and air quality.This effort will study new particle formation involving nitric acid, sulfuric acid, ammonia, and amines, and particle formation by highly oxygenated organic compounds from both terpene and aromatic precursors. Experiments seek to answer the following questions: (1) How do the temperature dependencies of autoxidation as well as peroxy-radical ‘dimerization’ reactions across different systems (i.e., α pinene−RO2 + isoprene−RO2 → ROOR+O2) combine to control particle formation and growth in “pure organic” systems? (2) Do oxidized-organic and acid-base systems interact synergistically or independently during particle formation and growth, or can they even ‘spoil’ each other and inhibit nucleation? The two interconnected projects will focus on the interactions between acids, bases, and highly oxidized (and polar) organics ranging from particle formation itself to growth up to 5-10 nm. Key issues are to determine when nitric acid participates directly in particle formation versus activating growth of formed particles, and whether the acid-base and organic particle formation pathways proceed independently in the atmosphere or interact, either synergistically or antagonistically. Observables including measured formation and growth rates, gas-phase vapor measurements, and particle composition will combine to tightly constrain these coupled systems. At CLOUD the CMU team will use an iodide chemical ionization mass spectrometer to measure the composition of gases and growing particles, the later by thermal desorption from teflon filters (FIGAERO CIMS).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.