Laboratory Studies of Photochemistry in Antarctic Snow and Ice

雪中的光化学反应可以对积雪的化学和组成以及上覆大气产生重要影响。 例如，最近在南极和北极的测量显示，阳光照射下的雪向大气中释放了一些重要的污染物。 我们理解和模拟这种化学的能力目前是有限的，部分原因是我们缺乏雪中一些重要化学物质的基本光化学信息。 该奖项支持的研究将有助于填补这一空白，通过表征这些关键物种中的三种：亚硝酸盐（NO2-），亚硝酸（HNO 2）和过氧化氢（HOOH）的低温光化学。 我们将使用我们最近在硝酸盐（NO3-）光化学研究中开发的一种敏感技术来测量这些反应在冰上的量子产率。 除了这项基础研究，我们还将测量在南极雪样本中的羟基自由基（OH），氮氧化物（NOx）和HOOH的形成率。 这些测量将是未来模型的重要输入，并将使我们能够测试已知物种（例如，NO3-、NO2-和HNO 2）负责大部分积雪反应性（例如，OH形成）。 总的来说，该奖项的结果将显着提高我们了解积雪化学的能力，以及对南极以及许多其他永久或季节性积雪地区大气的影响。 这些结果还将加强利用冰芯记录监测全球变化的努力。 除了这些影响之外，该奖项还将帮助培训学生和博士后研究员，这项工作的结果将被整合到两个班级中，以便让学生了解极地地区面临的一些重要问题。

Photochemical reactions in snow can have important effects on the chemistry and composition of the snowpack as well as the overlying atmosphere. For example, recent measurements in the Antarctic and Arctic have revealed that sunlit snow releases a number of important pollutants to the atmosphere. Our ability to understand and model this chemistry is currently limited, in part because we lack fundamental photochemical information for a number of important chemical species in snow. This award supports research that will help fill this gap by characterizing the low-temperature photochemistry of three of these key species: nitrite (NO2-), nitrous acid (HNO2), and hydrogen peroxide (HOOH). We will measure quantum yields for these reactions on ice using a sensitive technique that we recently developed during a study of nitrate (NO3-) photochemistry. In addition to this basic research, we will also measure the rates of formation of hydroxyl radical (OH), nitrogen oxides (NOx), and HOOH in illuminated Antarctic snow samples. These measurements will be important inputs for future models, and will allow us to test whether known species (e.g., NO3-, NO2- and HNO2) are responsible for most of snowpack reactivity (e.g., OH formation). Overall, results from this award will significantly improve our ability to understand snowpack chemistry, and the resulting effects on the atmosphere, both in the Antarctic as well as in the many other regions with permanent or seasonal snow. These results will also strengthen efforts to use ice core records to monitor global change. In addition to these impacts, this award will help train students and a postdoctoral fellow, and results from this work will be integrated into two classes in order to expose students to some of the important issues facing polar regions.