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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=744002
• 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。气溶胶的高质量浓度导致空气质量差，这是全球过早死亡的主要原因。在当前的COVID-19大流行期间，受感染者呼出的气溶胶也因其在病毒传播中的潜在作用而引起了广泛的公众关注和负面报道。气溶胶也是地球气候系统中复杂的辐射强迫因子。它们构成了气候预估中最大的不确定性来源之一。在有利的湿度条件下，气溶胶颗粒能否达到激活成云滴所需的临界尺寸，在很大程度上取决于它的化学成分和大小。成功激活成云滴的临界干燥尺寸通常在直径40到60纳米左右。颗粒的表面积体积比成为这个超细尺寸范围内的一个重要因素，构成了热力学平衡组成和相态的尺寸依赖性。位于空气/粒子界面的分子，即“表面”，与粒子内部（体积）相比，与邻近分子的相互作用不同，这导致了能量惩罚，表现为表面张力，或者更一般地说，界面能。理解和量化尺寸对颗粒体之间分子分配的影响，不同液相之间的表面和潜在内部界面，是至关重要的-因此是本研究计划的目标。环境气溶胶在化学上非常复杂，经常表现出所谓的液-液相分离，根据最近的发现，可能有三个或更多的液相。最近的高影响研究也表明，相分离可能对气溶胶成分和云的形成产生重要影响，但与尺寸对相变和颗粒特征的影响有关的许多具有挑战性的方面仍然知之甚少。该研究项目旨在利用我们在大气化学和物理领域的广泛专业知识，通过开发和应用独特的、高度先进的热力学和动力学模型，贡献原创的科学研究。我们将重点模拟表面和界面对气溶胶颗粒组成、相分离和水吸收的影响，覆盖整个大气感兴趣的颗粒大小范围。我们将进一步在详细模型和简化模型之间搭建桥梁；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培养学生提供极好的机会，并有望产生高影响力的科学研究。该项目将建立在国内和国际合作的基础上，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的工具。