Chemistry of Pollutants at Air-Ice Interfaces

我的工作将解决困扰积雪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的理解。环境模型通常把冰看作是一个固体的不反应的核心，上面覆盖着少量的液态水，其中发生了反应。然而，冰表面的物理性质不同于液态水表面（也不同于过冷水），我已经证明，空气-冰界面的反应动力学和机制与液态水和冰内液体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来实现：(1)测量空气-冰界面反应的动力学和产物；(2)利用拉曼和荧光显微镜对含溶质冰表面进行表征；(3)空气-冰界面物理和化学过程的空间分辨研究。这项工作的结果将使我们对冰作为一种化学反应器的理解，这是准确参数化模型所必需的，并将为这些模型中可以包含的重要反应提供速率常数。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和研究非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覆盖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，因为这个国家的大部分地区每年都会有部分时间被积雪覆盖。

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.