Collaborative Research: Impact of Snow Photochemistry on Atmospheric Radical Concentrations at Summit, Greenland

在过去的几年中，科学界对在阳光照射下的雪中发生的化学处理产生了极大的兴趣。积雪已被证明是整个对流层中光化学活性最强、氧化性最强的区域之一，而不仅仅是作为对流层反应产物的被动汇。在我们思考积雪在大气化学中的作用的这场革命中，为这项提议而聚集的研究小组发挥了核心作用。一个关键的发现是，雪发色团的光解引发了一些重要的微量气体的释放。最初的模型表明，许多这些气体（HCHO、HOOH、CH3CHO和HONO）的光解作用导致大量HOx（即OH和HO2）的产生，这反过来又导致积雪和雪上方空气中这些自由基的大量增强。由于OH氧化是许多对流层气体的主要汇，包括一些对气候变化和平流层O3消耗很重要的气体，因此HOx的增强可能会显著扰乱对流层化学。积雪化学也可能改变最终保存在冰川冰中的大气成分的化学记录。虽然最近的研究表明，积雪中的光化学和物理过程可以影响大气和积雪的化学和组成，但总的来说，人们对这些过程知之甚少。对于产生和消耗OH和HO2的过程尤其如此。该研究将阐明在广泛的环境条件下，在阳光照射的雪中产生和消耗OH和HO2自由基的过程，从而提高我们对这种独特环境下快速光化学的理解。

Lefer0220763In the past few years there has been an explosion of scientific interest in the chemical processing occurring in sunlit snow. Rather than simply acting as a passive sink for the products of tropospheric reactions, the snowpack has been shown to be one of the most photochemically active, and strongly oxidizing, regions of the entire troposphere. The group of investigators assembled for this proposal has played a central role in this revolution in our thinking about the role of the snowpack in atmospheric chemistry. One key finding has been that photolysis of snow chromophores initiates the release of a number of important trace gases. Initial modeling suggests that photolysis of a number of these gases (HCHO, HOOH, CH3CHO and HONO) results in an enormous production of HOx (i.e., OH and HO2), which in turn causes a large enhancement of these radicals in the snowpack and in the air just above the snow. Because oxidation by OH is the main sink for many tropospheric gases, including some of those important for climate change and stratospheric O3 depletion, this enhancement in HOx might significantly perturb tropospheric chemistry. Snowpack chemistry likely also modifies the chemical records of atmospheric composition ultimately preserved in glacial ice. While recent work has shown that photochemical and physical processes in the snowpack can impact the chemistry and composition of both the atmosphere and snowpack, these processes are, in general, poorly understood. This is especially true for the processes that produce and consume OH and HO2. The research will elucidate the processes that produce and consume OH and HO2 radicals within and above sunlit snow over a wide range of environmental conditions, thereby improving our understanding of fast photochemistry within this unique environment.