Tropospheric nitrogen oxides in the Anthropocene: Interfacial chemistry and novel analytical methods for quantification of organic nitrates and atmospheric radicals

点击翻译按钮获取中文摘要

Human activities have started to modify the planet's ecosystems and climate. My team's research will examine how some of these perturbations affect the atmospheric abundances of nitrogen oxides. In the troposphere (the lowest layer of the atmosphere), these compounds are involved in many important processes such as the formation of the criteria air pollutants ozone and PM2.5 (fine particulate matter suspended in air) whose health effects include respiratory and cardiovascular disease (i.e., higher risk of stroke) and predominantly affect people already marginalized by a low socio-economic status. The proposed research will focus on 3 aspects of atmospheric nitrogen oxide chemistry. A) Warmer temperatures have driven up emissions of volatile organic compounds (VOC) from vegetation. These compounds react with and sequester nitrogen oxides in the form of organic nitrates. The increase in VOC emissions coupled to a concurrent decline of NOx emissions from automobiles will accentuate the relative importance of organic nitrates in the troposphere. However, it is currently not well known what happens to the subset of organic nitrates predominantly formed in Canada. My team and I will build a new scientific instrument to study organic nitrate chemistry, called multicapillary column thermal dissociation cavity ring-down spectrometer. We will use this new tool to measure key kinetic parameters governing formation and removal of organic nitrates in the troposphere. Experiments will involve my group's atmospheric simulation chamber, identification of organic nitrates (e.g., by mass spectrometry), and measurement of air-water distribution coefficients and hydrolysis rates. B) There is no surer sign of the Anthropocene than the proliferation of polymer fragments throughout the Earth system, including the atmosphere. These fragments present a surface on which chemical reactions take place. The same surfaces also exist indoors and in urban areas (e.g., as sidings of buildings) and on the fuselages of modern aircraft. My team and I will study (i.e., measure rate constants, formulate mechanisms, etc.) interactions of nitrogen oxides with plastic surfaces, making use of state-of-the-art instruments previously developed in my group to quantify nitrogen oxides. C) Many of the VOC emitted from vegetation or by the oil and gas industry contain double bonds, which react with ozone to form Criegee intermediates (CIs). Methods to quantify these highly reactive compounds were only developed a decade ago, such that much of their chemistry still needs to be worked out. We will quantify CI concentrations by mass spectrometry and study reactions between CIs and nitrogen oxides, identifying products and determining rate constants. This work will train a diverse group of 15 HQP and improve our ability to accurately forecast air quality, assess the impact of climate change, and support the development of regulatory guidelines by govt. agencies, which matters to us all.