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

Dibb0221109在过去的几年里，人们对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，而不是简单地充当对流层反应产物的被动汇。为这项提案而聚集的研究小组在我们思考积雪在大气化学中的作用的这场革命中发挥了核心作用。一项重要发现是雪发色团的光解引发了许多重要的微量气体的释放。初步模型表明，许多此类气体（HCHO、HOOH、CH3CHO 和 HONO）的光解会导致大量产生 HOx（即 OH 和 HO2），进而导致积雪和雪上方空气中的这些自由基大量增强。由于 OH 的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 的这种增强可能会显着扰乱对流层化学。积雪的化学成分也可能改变了最终保存在冰川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会影响大气和积雪的化学和成分，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。该研究将阐明在各种环境条件下，在阳光照射的雪中和上方产生和消耗 OH 和 HO2 自由基的过程，从而提高我们对这种独特环境中快速光化学的理解。

Dibb0221109In 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.