醛酮类有机物在大气新粒子形成及生长过程中的协同竞争机制研究

New particle formation and its subsequent growth play a key role in air quality and climate change at regional and global scales. Currently, the mechanism of particle formation and growth as well as its environmental effects are still poorly understood. Thereby, fully understanding of the atmospheric nucleation and subsequent growth still presents a big challenge to atmospheric chemistry researches. Aldehydes and ketones compounds are common organic pollutants and provided with strong chemical reactivity. However, the study of aldehydes and ketones compounds on atmospheric new particle formation is rare. In this study, we propose to build a new flow tube reactor system, which can be synchronously study of the new particles formation and its subsequent growth. This research mainly through the atmospheric science and physical chemistry methods, using flow tube reactor, mass spectrometry, aerosol nucleation photoelectron imaging device, and combined with high accuracy quantum calculations and cluster dynamic simulations, to systematically study the aerosol nucleation systems, identifying the key precursors that involved in or contributed to the new particles formation and growth, studying the single organic compound or the organic compounds synergistic effects lead to the observed high nucleation rate in China, and further understanding the chemical and physical mechanisms that driving the initial and subsequent growth of new particles. Also, future researches could establish whole process tracking on new particle formation, from precursor, nucleation, growth till the environmental effects, by integrating flow tube simulation, quantum calculation, and dynamic simulations. Currently, the mechanism of highly efficient nucleation and rapid growth taking place under complex air pollution in China is urgently needed to be in-depth studied in order to improve our understanding of regional haze formation. This could be helpful to understand the similarity and difference in the nucleation mechanism between clean and polluted atmospheric environments.

新粒子的形成与生长是大气中颗粒物和云凝结核的重要来源。虽然不同类型的新粒子成核机理已被广泛提出，但还没有一种能够完全解释我国大气环境中较高的成核速率。醛酮类化合物作为大气中常见的含氧有机污染物，是挥发性有机物中化学反应活性较强的一类物质，但目前还没有针对这些反应性有机物参与新粒子形成的研究。鉴于此，本课题拟搭建一套流动管反应系统，用于同步研究新粒子的形成与增长过程，将流动管反应系统与质谱、光电子能谱联用，结合高精度量化计算及团簇动力学模型，充分识别参与并促进新粒子形成及生长的关键醛酮类有机物的类型，探究单一物种及多物种协同效应对新粒子形成及生长过程的影响，弄清驱动新粒子初始和后续增长的物理化学机制。通过本项目的研究，不仅可以揭示我国大气复合污染条件下快速成核和持续增长的条件与机制，评价新粒子对大气环境的影响，还可以提高我们对区域霾形成机制的认识。

新粒子生成是大气中重要的气态向颗粒态的二次转化过程，在全球尺度上是大气颗粒物的重要来源之一。鉴于醛酮类、高分子有机物、有机酸化合物等作为大气中常见的有机污染物，也是有机物中化学反应活性较强的一类物质，针对这些反应性有机物参与新粒子形成的过程，我们采用实验及理论相结合的方法，从微观角度进行系统研究。在项目执行过程中，我们首先搭建了一套流动管反应系统，用于同步研究新粒子的形成与增长过程，将流动管反应系统与质谱、SMPS联用，结合高精度量化计算及团簇动力学模型，充分识别参与并促进新粒子形成及生长的反应性有机物，探究单一物种及多物种协同效应对新粒子形成及生长过程的影响，弄清驱动新粒子初始和后续增长的物理化学机制。通过本项目的研究，我们发现在无水的情况下，醛酮类分子很难与硫酸分子耦合，团簇生长通道受阻，对NPF的影响较小，可以基本排除甲醛、丙酮等醛酮类物质能够直接参与成核。但是，醛酮类的衍生物可能会为醛酮类物质对NPF的影响提供新的方向。另外，成核团簇主要是通过氢键和质子转移相互作用形成相对稳定的团簇，并以此为平台逐步增长到较大尺寸，这些研究结果可以提高我们对区域霾形成机制的认识。