New Insights into the Formation and Evolution of Air Pollutants Via Atmospheric Multiphase Chemistry

大气气溶胶是指直径为平均人发直径的1/10至1/1000的悬浮颗粒。虽然气溶胶的体积很小，但它对21世纪最紧迫的两个环境问题产生了巨大的影响：空气污染和气候变化。气溶胶携带有害化学物质，可以深入呼吸道，影响人体健康。2012年，全世界有700万例死亡与环境和室内气溶胶有关。此外，悬浮的气溶胶可以通过反射阳光来抵消温室气体的变暖效应，从而对地球产生冷却效应。* 了解气溶胶的化学性质目前是一个重大的科学挑战。气溶胶冷却效应的毒性和大小仍然高度不确定。气溶胶的一个最不为人所知的方面也是其中的一个主要部分，被称为二次有机气溶胶（SOA），它含有数百种通过复杂的大气化学产生的未识别的有机化合物。这里提出的研究计划旨在解开导致SOA在大气中形成和持续演变的复杂化学过程。拟议研究的结果将指导大气化学家、环境毒理学家和流行病学家以及气候学家更好地评估气溶胶对环境的影响。这种评价为政策并最终为可持续的未来提供了基本准则。* *在第一个方向，我们将分析SOA中复杂的、未解决的部分，这是目前理解SOA化学的主要障碍。我们将开发用于直接测量的创新分析方法，避免过多的样品制备和处理，因为在这些过程中可能会损失精细和反应性化合物。采用新开发的和成熟的分析技术，我们将调查未知的化学物种和未发现的化学反应发生在SOA。** 第二个方向，我们会针对一个迫切的环境问题：固体燃料燃烧所造成的空气污染。全世界有30亿人使用固体燃料做饭，包括煤、木柴、农业残渣和动物粪饼。固体燃料燃烧造成的空气污染是全球范围内第三大健康风险因素。我们将分析固体燃料燃烧产生的气溶胶的化学成分知之甚少。我们会进一步研究固体燃料燃烧所排放的废气在大气中的化学成分，这些废气会产生有毒的化学污染物，影响本港以至整个区域的空气质素。

Atmospheric aerosol refers to suspended particles with diameters 1/10 to 1/1000 that of an average human hair. Although small in size, aerosol exerts a huge impact on two of the arguably most emergent environmental issues of the 21st century: air pollution and climate change. Carrying harmful chemicals with it, aerosol can penetrate deep into the respiratory tract, affecting human health. In 2012, 7 million deaths worldwide were associated with ambient and indoor aerosol. Additionally, suspended aerosol can offset the warming effect of greenhouse gases by reflecting sunlight, which gives rise to a cooling effect on the planet. ******Understanding the chemistry of aerosol is currently a major scientific challenge. The toxicity and the magnitude of the aerosol cooling effect remain highly uncertain. One of the least understood aspects of aerosol is also a major fraction of it, referred to as Secondary Organic Aerosol (SOA), that contains hundreds of unidentified organic compounds produced through complex atmospheric chemistry. The research program proposed here aims to unravel the complex chemistry that leads to the formation and continuous evolution of SOA in the atmosphere. The outcome of the proposed research will guide the efforts of atmospheric chemists, environmental toxicologists and epidemiologists, as well as climatologists to better evaluate the environmental impact of aerosol. Such evaluations provide essential guidelines for policies, and ultimately, for a sustainable future. ******The proposed research program has two research directions. In the first direction, we will analyze the complex, unresolved fraction of SOA that is currently a major obstacle in understanding the SOA chemistry. We will develop innovative analytical methods for a direct measurement that avoids excess sample preparation and treatment, since delicate and reactive compounds can be lost during such processes. Employing both newly-developed and well-established analytical techniques, we will investigate the unidentified chemical species and undiscovered chemical reactions taking place in SOA. ******In the second direction, we will target an urgent environmental problem: air pollution from solid fuel burning. Solid fuel, including coal, firewood, agriculture residue and animal dung cake, is used by 3 billion people worldwide for cooking. Air pollution from solid fuel burning is the third most important health risk factor on the global scale. We will analyze the poorly understood chemical composition of aerosol arising from solid fuel burning. We will further study the atmospheric chemistry of emissions from solid fuel burning, which can give rise to toxic chemical pollutants and affect the air quality at a local to regional scale.