The Acidity of the Quasi-Liquid Layers of Ice and Snow

本项目的目的是通过光谱原位pH探针测量与环境相关的冷冻电解质溶液的酸度。核磁共振（NMR）将用于区分流体和固体区域的性质。固态魔角旋转核磁共振光谱测量将用于监测嵌入在与环境相关的冷冻电解质溶液中的微观流体的局部酸度。这些材料中酸度的空间分布将通过冷冻含水电解质和使用磁共振成像（MRI）与pH探针相结合来获得。灵敏的荧光pH探针的替代使用也将被探索。这项工作将提供微流体湿润多晶冰（如在冰雪中发现的冰）中的化学环境信息。这些液体的离子组成与冰本身截然不同，并且可能具有非常不同的酸度。局部酸度决定了弱挥发性酸或碱能否在冰和气相之间交换，或者在冷冻介质中掺杂剂之间的反应是否被抑制或催化。举例来说，南极洲和格陵兰岛阳光照射下的积雪中亚硝酸的不同进化表明，我们需要更好地了解控制冰酸度的因素。这个项目将提供基本的理解，这将导致对非常重要的环境问题的见解，关于发生在冰雪界面的化学性质和光化学过程。由于这些研究的基本性质，在其他科学和工程领域的应用可能是可能的。该项目将提供从K-12到研究生阶段的教育和培训机会。

The intent of this project is to measure the acidity of frozen electrolyte solutions of environmental relevance by means of spectroscopic in situ pH probes. Nuclear magnetic resonance (NMR) will be used to distinguish the properties of the fluid and solid regions. Solid-state magic angle spinning NMR spectroscopic measurements will be used to monitor the local acidity of the microscopic fluids embedded in frozen electrolyte solutions of environmental relevance. The spatial distribution of acidity in these materials will be obtained by freezing aqueous electrolytes and using magnetic resonance imaging (MRI) in conjunction with the pH probes. The alternative use of sensitive fluorescent pH probes will also be explored. This work will provide information on the chemical environment in microfluids wetting polycrystalline ices, such as those found in ice and snow. These fluids have drastically different ionic composition than the ice itself, and may have very different acidities. Local acidity determines whether weak volatile acids or bases can be exchanged between ice and the gas phase, or whether reactions between dopants are inhibited or catalyzed in frozen media. As an example, the dissimilar evolution of nitrous acid from sunlit snow packs in Antarctica and Greenland points to the need for a better understanding of the factors controlling ice acidity. This project will provide fundamental understanding that will lead to insights on very important environmental questions regarding the chemical properties and photochemical processes that occur at the interfaces of ice and snow. Because of the fundamental nature of these studies, applications in other areas of science and engineering may be possible. The project will provide opportunities for education and training from the K-12 through graduate level.