Mechanism for intense photochemical NOx fluxes from ice surfaces

在南极洲、格陵兰岛、加拿大北极和许多其他永久或季节性积雪覆盖的地区，观测到的强烈光化学NOx通量的来源是雪中硝酸盐的光解。数值模型未能对这种控制极地边界层氧化潜势的现象提供充分的解释。这突显了我们在分子水平上对机理的认识不足，以及缺乏适当的物理参数来描述冰中硝酸盐的异相光解速率。此外，有几个迹象表明，可能存在相当大的偏向，倾向于从吸附或分离到雪粒表面的硝酸盐产生光产物。我们建议研究控制冰表面光解速率的因素，并量化它们的表面特异性。使用薄冰膜替代物，我们将研究最重要的物理参数，试图提供分子水平的机制描述这一现象。这将使对光化学通量的定量评估成为可能，并改进对冰芯气候指标的解释。在2007-2008国际极年来临之际，这些以实验室为基础的定量调查是重要和及时的。

Photolysis of snow-bound nitrates has been identified as the source for intense photochemical NOx fluxes that have been observed to emanate for the sunlit snow pack in Antarctica, Greenland, the Canadian arctic and many other permanently or seasonally snow covered regions. Numerical models have failed to provide an adequate interpretation for this phenomenon which controls the oxidative potential of the polar boundary layer. This highlights our poor understanding of the mechanisms at the molecular level and the lack of appropriate physical parameters to describe the heterogeneous photolysis rates of nitrates in ice. Furthermore, there are several indications that there might be a considerable bias favouring photoproducts from nitrates adsorbed or segregated to the surface of snow grains. We propose to investigate the factors that control the photolysis rate at ice surfaces and quantify their surface specificity. Using thin ice film surrogates, we will investigate the most important physical parameters in an attempt to provide a molecular-level mechanistic description of this phenomenon. This will enable a quantitative evaluation of the photochemical fluxes and improve the interpretation of climate proxies from ice cores. These quantitative laboratory-based investigations are important and timely at the dawn of the International Polar Year 2007-2008.