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

大气气溶胶是指直径为人类头发的1/10至1/1000的悬浮颗粒。虽然体积很小，但气溶胶对21世纪最紧迫的两个环境问题——空气污染和气候变化——产生了巨大的影响。气溶胶携带有害化学物质，可深入呼吸道，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项重大的科学挑战。气溶胶冷却效果的毒性和强度仍然高度不确定。气溶胶的一个最不为人所知的方面也是它的一个主要部分，被称为二次有机气溶胶（SOA），它包含数百种通过复杂的大气化学产生的未知有机化合物。这里提出的研究计划旨在揭示导致SOA在大气中形成和持续发展的复杂化学过程。拟议研究的结果将指导大气化学家、环境毒理学家、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。这种评价为政策提供了基本的指导方针，并最终为可持续的未来提供了指导方针。本研究计划有两个研究方向。在第一个方向上，我们将分析SOA中复杂的、未解决的部分，这些部分目前是理解SOA化学过程的主要障碍。我们将开发用于直接测量的创新分析方法，避免过量的样品制备和处理，因为在这些过程中可能会丢失微妙和活性化合物。我们将采用新开发的和成熟的分析技术，研究SOA中未发现的化学物质和未发现的化学反应。在第二个方向上，我们将针对一个紧迫的环境问题：固体燃料燃烧造成的空气污染。固体燃料，包括煤、木柴、农业残渣和动物粪饼，被全世界30亿人用于烹饪。固体燃料燃烧产生的空气污染是全球第三大最重要的健康风险因素。我们将分析固体燃料燃烧产生的气溶胶的化学成分。我们将进一步研究固体燃料燃烧排放的大气化学，这可能会产生有毒化学污染物，影响局部到区域范围的空气质量。

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.