Mechanism for intense photochemical NOx fluxes from ice surfaces

雪中硝酸盐的光解被确定为强烈的光化学氮氧化物通量的来源，在南极洲、格陵兰岛、加拿大北极地区和许多其他永久或季节性积雪地区，已观察到这些通量从阳光照射的积雪中散发出来。 数值模型未能提供一个充分的解释这种现象，控制极边界层的氧化电位。 这突出了我们在分子水平上对机制的理解不足，以及缺乏适当的物理参数来描述冰中硝酸盐的异质光解速率。 此外，有几个迹象表明，可能有一个相当大的偏见有利于从硝酸盐吸附或分离到雪粒表面的光产物。 我们建议调查的因素，控制在冰表面的光解速率和量化其表面特异性。 使用薄的冰膜替代品，我们将调查最重要的物理参数，试图提供一个分子水平的机制描述这种现象。 这将有助于对光化学通量进行定量评估，并改善对冰芯气候代用指标的解释。 在2007-2008国际极地年即将到来之际，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.