Aerosol chemistry and photochemistry in polluted urban environments: research for tomorrow's megacities

尽管我们目前对城市空气质量的了解主要来自于在北美和西欧进行的研究，但今天的城市增长主要发生在亚洲和非洲的发展中特大城市。我们小组研究的主要目标是探索光诱导化学(光化学)，这种化学可能在发展中的城市地区和受工业影响的地区典型的富含金属和烟尘的大气颗粒物(气溶胶)中得到促进，从而提高我们对这些未被研究的环境中控制空气质量的过程的理解。我们将探索真实的、化学成分复杂的气溶胶样品表面的化学和光化学，我们将在加拿大和国外的各种受污染的城市和受工业影响的环境中收集这些样品。为了更好地了解气溶胶化学对痕量污染物浓度的影响，我们将研究臭氧、亚硝酸盐和二氧化硫与这些气溶胶样品的萃取物制备的薄膜之间的光化学作用。此外，我们将研究金属催化的光化学对有机硫酸盐(OS；ROSO3-)和有机硝酸盐(On；RONO2)化合物气相形成的可能性，这两种化合物已被证明对城市周围气溶胶中的有机质量有很大贡献。*我们还将努力提高我们对尘埃和城市有机污染物之间光化学相互作用的分子性质和大气后果的理解。在这里，我们的目标是在实验室中复制在城市周围条件下将有机物质沉积在尘埃气溶胶上的过程，进而捕捉这些过程在颗粒上留下的形态特征。为了更好地了解颗粒形态在影响粉尘-碳质混合气溶胶表面反应中所起的作用，我们将比较来自源土壤的新鲜产生的粉尘气溶胶表面与先前涂有单一有机化合物和复杂有机混合物的粉尘气溶胶表面对臭氧、NO2和SO2的光化学吸收-特别是发展中经济体中使用的典型高污染发动机的废气。我们还将在新建的大气反应室中研究粉尘与污染物在较长时间尺度上的相互作用：具体地说，我们将研究粉尘催化新颗粒的形成和气相有机物的氧化；此外，我们还将研究光活性粉尘气溶胶对城市有机污染物形成的二次有机气溶胶(SOA)的数量和组成的影响。

Although our current understanding of urban air quality comes largely from studies conducted in North America and Western Europe, the bulk of today's urban growth is occurring in developing Asian and African megacities. The overarching goal of our group's research is to explore light-induced chemistry (photochemistry) that may be promoted in the metal- and soot-rich atmospheric particulate matter (aerosol) typical of developing urban regions and industrially influenced areas, and thus improve our understanding of the processes that govern air quality in these understudied environments.******We will explore chemistry and photochemistry at the surface of real, chemically complex aerosol samples, which we will collect in a variety of polluted urban and industrially influenced environments, both in Canada and abroad. In an effort to better understand the influence of aerosol-phase chemistry on the concentrations of trace pollutant gases, we will study the photochemical interactions of O3, NO2 and SO2 with thin films prepared from extracts of these aerosol samples. In addition, we will investigate the possibility that metal-catalyzed photochemistry contributes to the aerosol-phase formation of organosulfate (OS; ROSO3–) and organonitrate (ON; RONO2) compounds, both of which have been shown to contribute significantly to the organic mass present in ambient urban aerosol.******We will also work to improve our understanding of the molecular nature and atmospheric consequences of photochemical interactions between dust and urban organic pollutants. Here, we will aim to replicate in the laboratory the processes that deposit organic material on dust aerosol under ambient urban conditions and, by extension, capture the morphological characteristics imprinted on particles by these processes. In an effort to better understand the role that particle morphology plays in influencing reactions at the surface of mixed dust–carbonaceous aerosol, we will compare the photochemical uptake of O3, NO2 and SO2 at the surface of dust aerosol freshly generated from source soils with that at the surface of dust aerosol previously coated with single organic compounds and complex organic mixtures—specifically, exhaust from highly polluting engines typical of those used in developing economies. We will also study dust–pollutant interactions over longer timescales in a newly constructed atmospheric reaction chamber: specifically, we will investigate dust-catalyzed formation of new particles and oxidation of gas-phase organics; in addition, we will investigate the influence of photoactive dust aerosol on the quantity and composition of secondary organic aerosol (SOA) formed from urban organic pollutants.**