Chemistry of Pollutants at Air-Ice Interfaces

我的工作将解决困扰雪覆盖地区大气化学的主要知识空白之一，即我们对空气-冰界面的反应动力学和机制缺乏基本了解。环境模型通常将冰视为一个固体、无反应的核心，被少量的液态水覆盖，在其中发生反应。然而，冰表面的物理性质与液态水表面不同(也不同于过冷水)，我已经证明了空气-冰界面上的反应动力学和机制可能与液态水和冰内液态区域的反应动力学和机制有很大不同。我将研究溶质对空气-冰界面的组成、极性和物理状态等性质的影响，并将这些性质与反应性联系起来。这将通过三个具体目标实现：(1)测量空气-冰界面的动力学和反应产物；(2)用拉曼和荧光显微镜表征含有溶质的冰表面；(3)对空气-冰界面的物理和化学过程进行空间分辨研究。这项工作的结果将使我们对冰作为化学反应的理解，这是准确地将模型参数化所必需的，并将提供可以包括在这些模型中的重要反应的速率常数。这项工作的预期影响包括更好地预测积雪地区的污染物命运，以及研究不均匀大气过程的新方法。拟议工作的结果可能最终提高我们对积雪地区污染物对健康影响的理解和缓解。这项工作与加拿大非常相关，因为该国大部分地区一年中有一部分时间会被积雪覆盖。

My work will address one of the major knowledge gaps afflicting atmospheric chemistry in snow-covered regions, which is our lack of fundamental understanding of reaction kinetics and mechanisms at air-ice interfaces. Environmental models often treat ice as a solid unreactive core covered by a small volume of liquid water in which reactions occur. However, the physical properties of ice surfaces are distinct from those of liquid water surfaces (and also distinct from supercooled water), and I have demonstrated that reaction kinetics and mechanisms at air-ice interfaces can differ significantly from those in liquid water and in liquid regions within ice. I will investigate the effects of solutes on properties such as composition, polarity, and physical state of air-ice interfaces, and will relate these properties to reactivity. This will be achieved through three specific aims: (1) measurement of kinetics and products of reactions at air-ice interfaces; (2) characterization of solute-containing ice surfaces with Raman and fluorescence microscopy; and (3) spatially-resolved investigations of physical and chemical processes at air-ice interfaces. The results of this work will provide us with the understanding of ice as a chemical reactor that is necessary to parameterize models accurately, and will provide rate constants for important reactions that can be included in these models. Anticipated impacts of this work include better predictions of pollutant fate in snow-covered regions and novel methods of investigating heterogeneous atmospheric processes. The results of the proposed work may ultimately improve our understanding - and mitigation - of the health implications of pollutants in snow-covered regions. This work is extremely relevant to Canada, as much of the country experiences snow cover for some fraction of the year.