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面的大气产生重要影响。例如，最近在南极和北极进行的测量显示，阳光普照的雪向大气释放了许多重要的污染物。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种的基本光化学信息。该奖项支持有助于填补这一空白的研究，通过表征这些关键物种中的三个物种的低温光化学：亚硝酸盐(NO2-)、亚硝酸(HNO2)和过氧化氢(HoOH)。我们将使用我们最近在研究硝酸盐(NO3-)光化学时开发的一种灵敏技术来测量这些反应在冰上的量子产率。除了这项基础研究外，我们还将测量南极照明雪样中羟基自由基(OH)、氮氧化物(NOx)和HoOH的形成速度。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的物种(例如，NO3-、NO2-和HNO2)是否对大部分积雪反应(例如，OH的形成)负责。总体而言，这一奖项的结果将显著提高我们理解积雪化学及其对大气的影响的能力，无论是在南极还是在许多其他有永久性或季节性降雪的地区。这些成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，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，以便让学生接触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.