Quantifying the interplay of particle size, composition and phase separation: development of size-dependent aerosol thermodynamics and dynamics models for improved simulations of air quality and aerosol-cloud interactions

量化颗粒尺寸、成分和相分离的相互作用：开发尺寸相关的气溶胶热力学和动力学模型，以改进空气质量和气溶胶-云相互作用的模拟

• 批准号: RGPIN-2021-02688
• 负责人: Zuend, Andreas
• 金额: $ 2.19万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742156
• 关键词: Quantifying; interplay; particle; size; composition

Atmospheric aerosols are microscopically tiny, invisible particles suspended in the air. High mass concentrations of aerosols lead to poor air quality - a leading cause of premature deaths globally. During the ongoing COVID-19 pandemic, aerosols from exhalation of infected people have also gained broad public interest and bad press due to their potential role in virus transmission. Aerosols are also complex radiative forcing agents in Earth's climate system. They constitute one of the largest sources of uncertainty in climate projections. Whether an aerosol particle can reach a critical size necessary to activate into a cloud droplet under favorable humidity conditions depends strongly on its chemical composition and size. The critical dry size for successful activation into a cloud droplet is usually around 40 to 60 nm diameter. The surface area to volume ratio of particles becomes an important factor in this ultrafine size range, constituting a size dependence of the thermodynamic equilibrium composition and phase state. Molecules situated at the air/particle interface, i.e. the "surface", experience differing interactions with neighboring molecules compared to the particle interior (bulk), which leads to an energetic penalty manifesting itself as surface tension or, more generally, interfacial energy. Understanding and quantifying size effects on the partitioning of molecules between the particle bulk, the surface and potential interior interfaces between different liquid phases, is critical - hence a goal of this research program. Ambient aerosols are chemically very complex, often exhibiting so called liquid-liquid phases separation and, according to recent findings, potentially three or more liquid phases. Recent high-impact studies have also shown that phase separation can be an important influence on aerosol composition and cloud formation, yet a number of challenging aspects related to size effects on phase transitions and particle characteristics remain poorly understood. This research program aims to contribute original scientific research with the development and application of unique, highly advanced thermodynamic and dynamic models, drawing from our extensive expertise in this field of atmospheric chemistry and physics. We will focus on modeling the effects of surfaces and interfaces on aerosol particle composition, phase separation and water uptake over the whole range of particle sizes of atmospheric interest. We will further build bridges between detailed and reduced-complexity models; the latter for use in large-scale air quality and chemistry climate models. The proposed research will offer excellent opportunities for the training of students at McGill University with the prospect of generating high-impact scientific studies. The program will build upon national and international collaborations, lead to knowledge exchange with the community in Canada, and provide new tools for aerosol and air quality experts around the globe.

大气气溶胶是悬浮在空气中的微小的、看不见的颗粒。气溶胶质量浓度高导致空气质量差，这是全球过早死亡的主要原因。在持续的 COVID-19 大流行期间，感染者呼出的气溶胶由于其在病毒传播中的潜在作用也引起了公众的广泛关注和负面报道。气溶胶也是地球气候系统中复杂的辐射强迫剂。它们构成了气候预测中最大的不确定性来源之一。气溶胶颗粒是否能够达到在有利的湿度条件下激活成云滴所需的临界尺寸在很大程度上取决于其化学成分和尺寸。成功活化成云滴的临界干燥尺寸通常为直径 40 至 60 nm 左右。颗粒的表面积与体积之比成为该超细尺寸范围内的重要因素，构成热力学平衡组成和相状态的尺寸依赖性。与颗粒内部（体积）相比，位于空气/颗粒界面（即“表面”）的分子与相邻分子经历不同的相互作用，这导致能量损失，表现为表面张力或更一般地界面能量。了解和量化颗粒体积、不同液相之间的表面和潜在内部界面之间分子分配的尺寸效应至关重要，因此也是该研究项目的目标。环境气溶胶的化学性质非常复杂，通常表现出所谓的液-液相分离，并且根据最近的发现，可能存在三个或更多液相。最近的高影响力研究还表明，相分离可能对气溶胶成分和云形成产生重要影响，但与尺寸对相变和颗粒特征的影响相关的许多具有挑战性的方面仍然知之甚少。该研究计划旨在利用我们在大气化学和物理领域的丰富专业知识，通过开发和应用独特、高度先进的热力学和动力学模型来贡献原创科学研究。我们将专注于模拟表面和界面对大气感兴趣的整个颗粒尺寸范围内的气溶胶颗粒组成、相分离和吸水量的影响。我们将进一步在详细模型和降低复杂度模型之间建立桥梁；后者用于大规模空气质量和化学气候模型。拟议的研究将为麦吉尔大学的学生提供极好的培训机会，并有望产生高影响力的科学研究。该计划将以国内和国际合作为基础，促进与加拿大社区的知识交流，并为全球气溶胶和空气质量专家提供新工具。