Probing the Molecular Basis of the "Burying" Mechanism: An Additional Route to Secondary Organic Aerosol (SOA) Particle Growth

这个项目的重点是研究大气中新粒子生长的新机制。固体和半固体二次有机气溶胶（SOA）颗粒生长机制的不确定性限制了预测其对能见度、健康和气候影响的能力，从而限制了最优控制策略的发展。这项研究将提供基本的动力学和热力学数据，这将有助于发展和提高这种预测能力。了解有机颗粒的表面组成对于理解进入气体与表面的相互作用以及这如何影响它们的吸收和对颗粒生长的贡献至关重要。在分子水平上，预计气体在高粘性颗粒表面的停留时间将在它们的净吸收中起主要作用，但关于决定这种停留时间的基本参数的数据很少。本研究的最终目标是阐明一种假设的“掩埋”机制，该机制将气相物质纳入高粘性颗粒中。这种“埋藏”机制的一个核心方面是气体表面相互作用的性质。实验的具体目标是：(1)测量自组装单层（sam）上一系列选定结构和官能团的气体的吸收系数作为温度的函数，这些自组装单层（sam）具有明确定义的终端基团，也是SOA粒子和SOA本身的共同组成部分；(2)对最初吸附在SAMs上的选定气体进行温度编程热解吸研究，以获得动力学数据，从而确定不同温度下解吸的速率常数；(3)研究具有独特特征的低挥发性物种对臭氧分解形成的SOA颗粒吸收有机硝酸盐的影响，重点研究α-蒎烯。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 is focused on the investigation of a novel mechanism for the growth of new particles in the atmosphere. Uncertainties in the growth mechanisms of solid and semi-solid secondary organic aerosol (SOA) particles limit the ability to predict their impacts on visibility, health and climate, and hence the development of optimal control strategies. The research will provide the basic kinetic and thermodynamic data that will aid in developing and improving this predictive capability.Understanding the surface composition of organic particles is central to understanding the interaction of incoming gases with the surface and how this affects their uptake and contribution to particle growth. On a molecular level, it is expected that the residence time of gases on the surface of highly viscous particles will play a major role in their net uptake, yet there are few data on the fundamental parameters that determine this residence time. The ultimate goal of this research is to elucidate a hypothesized "burying" mechanism that incorporates gas phase species into highly viscous particles. A central aspect of this “burying” mechanism is the nature of the gas-surface interaction.The specific objectives of the experiments are to: (1) measure uptake coefficients as a function of temperature for a series of gases of selected structures and functional groups on self-assembled monolayers (SAMs) having well-defined terminal groups that are also common components of SOA particles as well as on SOA itself; (2) carry out temperature-programmed thermal desorption studies of the selected gases initially adsorbed on the SAMs to obtain kinetics data that will allow rate constants for desorption at different temperatures to be determined; and (3) carry out studies of the impact of lower volatility species with unique signatures on the uptake of organic nitrates into SOA particles formed from the ozonolysis of selected biogenics, with a focus on α-pinene.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.