Atmosperic and interfacial reaction dynamics

大气和界面反应动力学

• 批准号: RGPIN-2019-04757
• 负责人: Donaldson, DJames
• 金额: $ 3.5万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=748351
• 关键词: Atmosperic; interfacial; reaction; dynamics

Surfaces exposed to the atmosphere control many key atmospheric processes, such as activation of halides at snow and sea surfaces, loss of nitrogen oxide compounds, inhibition of heterogeneous aqueous chemistry by organic coatings and photochemical recycling of nitrates deposited on urban surfaces. An overarching theme of our research program is to relate the chemical morphology of various atmospheric surfaces to  heterogeneous reactivity. This work will build on the advances we have made during the past and will introduce some new tools as well. We will concentrate on aqueous systems, both liquid and frozen. (1) We will explore whether differences in solution photochemistry observed for natural organic material in seawater manifest as different interfacial photochemistry at sea surfaces. Glancing-angle LIF methods will measure adsorption isotherms for the samples at the freshwater and seawater surfaces, in the absence and presence of an artificial surface microlayer, to establish how effectively they may act as photosensitizers at the air-water boundary. In collaboration with the Lyon group, we will use PTR-MS to measure gas phase organic compound emission from illuminated freshwater and seawater samples containing these compounds. We will infer the production of organic radicals adsorbed at the water surface via the reaction of NO with R-O2. These experiments will provide key data concerning differences in the formation and chemical reactions of atmospheric oxidants and radicals at seawater and freshwater surfaces. (2) We will use quantum chemical and molecular dynamics tools to understand the reason(s) for the differences between the exclusion behaviors of nitrate and sulfate anions during freezing of aqueous solutions. We will combine different Raman probes with gas phase nitrogen oxide detection to relate the solvation state and specific location of the nitrate in frozen solutions to its photoreactivity. New experiments will be initiated using an x-ray beamline of a synchrotron source (at the Canadian Light Source or at the Paul Sherer Institute in Switzerland) to determine whether nitrate is co-located with other ions differently at the air interface than within the ice matrix. (3) We will monitor heterogeneous atmospheric chemistry within droplets, in real time. We intend to: (a) fully explore the morphology changes associated with evaporating mixed organic-inorganic drops, to understand the processes responsible. (b) Further develop spectroscopic probes to measure heterogeneous kinetics within droplets. Specifically, we will use absorption and Raman probing within the droplets (to monitor pH and composition) and gas phase NOx measurements in the surrounding air to explore the reason(s) for the different responses of NO2 and CO2 to organic coatings during interfacial transport. (c) Use laser-based Raman and fluorescence probes to interrogate composition (and kinetics) differences in the bulk vs. near-surface regions of the droplet.

暴露在大气中的表面控制着许多关键的大气过程，如雪和海面上卤化物的活化、氮氧化物化合物的损失、有机涂层对非均相水化学的抑制以及沉积在城市表面的硝酸盐的光化学再循环。我们研究计划的一个首要主题是将各种大气表面的化学形态与非均相反应性联系起来。这项工作将建立在我们过去取得的进展的基础上，并将引入一些新的工具。我们将专注于含水系统，包括液体和冷冻系统。 (1)我们将探讨是否在溶液中观察到的天然有机物质在海水中的光化学差异表现为不同的界面在海面上的光化学。掠射角LIF方法将测量淡水和海水表面样品的吸附等温线，在人工表面微层的存在和不存在的情况下，以确定它们在空气-水边界作为光敏剂的有效性。在与里昂小组的合作中，我们将使用PTR-MS来测量含有这些化合物的照明淡水和海水样品的气相有机化合物排放。我们将推断通过NO与R-O2的反应在水表面吸附的有机自由基的产生。这些实验将提供关于大气氧化剂和自由基在海水和淡水表面的形成和化学反应差异的关键数据。(2)我们将使用量子化学和分子动力学工具来理解硝酸根和硫酸根阴离子在水溶液冷冻过程中排斥行为差异的原因。我们将联合收割机不同的拉曼探针与气相氮氧化物检测相关联的溶剂化状态和特定位置的冷冻溶液中的硝酸盐，其光反应性。新的实验将使用同步加速器源的X射线光束线（在加拿大光源或在瑞士的Paul Sherer研究所）启动，以确定硝酸盐是否与其他离子在空气界面处的位置不同，而不是在冰基质中。 (3)我们将真实的实时监测液滴内的异质大气化学成分。我们打算：（a）充分探索与蒸发有机-无机混合液滴相关的形态变化，以了解相关过程。(b)进一步开发光谱探针，以测量液滴内的非均匀动力学。具体来说，我们将使用液滴内的吸收和拉曼探测（以监测pH值和组成）以及周围空气中的气相氮氧化物测量来探索NO2和CO2对有机涂层的不同响应的原因界面传输。(c)使用基于激光的拉曼和荧光探针来询问液滴的本体与近表面区域中的组成（和动力学）差异。