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

人类活动已经开始改变地球的生态系统和气候。我的团队将研究这些扰动如何影响大气中氮氧化物的丰度。在对流层（大气的最底层），这些化合物参与了许多重要过程，例如标准空气污染物臭氧和PM2.5（悬浮在空气中的细颗粒物）的形成，其健康影响包括呼吸系统和心血管疾病（即中风风险更高），主要影响已经被社会经济地位低下边缘化的人。拟开展的研究将集中在大气氮氧化物化学的3个方面。A)气温升高导致植物挥发性有机化合物（VOC）的排放增加。这些化合物以有机硝酸盐的形式与氮氧化物反应并隔离它们。VOC排放量的增加加上汽车NOx排放量的同时下降，将强调对流层中有机硝酸盐的相对重要性。然而，目前还不清楚在加拿大主要形成的有机硝酸盐的子集发生了什么。我和我的团队将建立一个新的科学仪器来研究有机硝酸盐化学，叫做多毛细管柱热解离腔衰荡光谱仪。我们将使用这个新工具来测量对流层中有机硝酸盐形成和去除的关键动力学参数。实验将涉及我小组的大气模拟室，有机硝酸盐的鉴定（例如，通过质谱法），以及空气-水分配系数和水解速率的测量。B)在整个地球系统，包括大气层中，聚合物碎片的扩散是人类世最可靠的迹象。这些碎片呈现出发生化学反应的表面。同样的表面也存在于室内和城市地区（例如，作为建筑物的侧面）以及现代飞机的机身上。我和我的团队将研究（即测量速率常数，制定机制等）氮氧化物与塑料表面的相互作用，利用我的小组以前开发的最先进的仪器来量化氮氧化物。C)植物或石油和天然气工业排放的许多挥发性有机化合物含有双键，它与臭氧反应形成Criegee中间体（CIs）。量化这些高活性化合物的方法在十年前才被开发出来，因此它们的大部分化学成分仍有待研究。我们将通过质谱法定量CI浓度，研究CI和氮氧化物之间的反应，鉴定产物并确定速率常数。这项工作将培养一支由15名HQP组成的多元化团队，提高我们准确预测空气质量、评估气候变化影响的能力，并支持政府机构制定监管指南，这对我们所有人都很重要。

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.