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地区，已观察到，积雪结合硝酸盐的光解作用是强烈的光化学NOx通量的来源。数值模式未能对这种控制极地边界层氧化电位的现象提供充分的解释。这突出了我们在分子水平上对机制的理解不足，并且缺乏适当的物理参数来描述硝酸盐在冰中的非均匀光解速率。此外，有几个迹象表明，可能有相当大的偏向于从硝酸盐吸附或分离到雪颗粒表面的光产物。我们建议研究控制冰表面光解速率的因素，并量化其表面特异性。利用薄冰膜替代物，我们将研究最重要的物理参数，试图提供这一现象的分子水平机制描述。这将能够对光化学通量进行定量评价，并改进对冰芯气候代用物的解释。在2007-2008国际极地年即将来临之际，这些基于实验室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.