Formaldehyde in the Alaskan Arctic snowpack: Partitioning and physical processes involved in air-snow exchanges
Formaldehyde in the Alaskan Arctic snowpack: Partitioning and physical processes involved in air-snow exchanges
复制标题
阿拉斯加北极积雪中的甲醛：涉及空气-雪交换的分区和物理过程
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
D. Richter
中科院分区：
文献类型：
--
作者：
M. Barret;F. Dominé;S. Houdier;J. Gallet;P. Weibring;J. Walega;A. Fried;D. Richter
[1]积雪是一种光化学活性介质，它产生许多与极地地区大气化学有关的关键活性物质。甲醛(HCHO)是雪中产生的一种活性物质，可以释放到大气边界层中。基于大气和雪的测量，这项研究调查了在2009年在阿拉斯加州巴罗举行的绿洲野外活动中观测到的六六六空气-雪交换所涉及的物理过程。新鲜的钻石尘埃层中的甲醛浓度变化可以通过甲醛在冰中的固溶体平衡，通过甲醛在雪晶中的固态扩散来定量解释。由于甲醛在冰中的扩散很慢，雪晶的大小是交换动力学中的一个主要变量，因此了解雪的比表面积至关重要。因此，不必考虑冰晶表面的准液态层中发生的过程，就可以解释甲醛的空气-雪交换。随着雪中甲醛浓度的增加，甲醛进入大气的通量也随之增加，这表明地面雪中存在着光化学产物。这项研究还表明，Alert(加拿大北极)和Barrow的溴化学差异导致了不同的雪成分和沉积后演化。巴罗的高活性溴化学可能导致了钻石尘埃形成的海拔高度的低甲醛浓度。随后，沉淀的钻石粉尘在热力学平衡方面是不饱和的，这与以前研究中在其他地方观察到的情况形成了对比。
[1] The snowpack is a photochemically active medium which produces numerous key reactive species involved in the atmospheric chemistry of polar regions. Formaldehyde (HCHO) is one such reactive species produced in the snow, and which can be released to the atmospheric boundary layer. Based on atmospheric and snow measurements, this study investigates the physical processes involved in the HCHO air‐snow exchanges observed during the OASIS 2009 field campaign at Barrow, Alaska. HCHO concentration changes in a fresh diamond dust layer are quantitatively explained by the equilibration of a solid solution of HCHO in ice, through solid‐state diffusion of HCHO within snow crystals. Because diffusion of HCHO in ice is slow, the size of snow crystals is a major variable in the kinetics of exchange and the knowledge of the snow specific surface area is therefore crucial. Air‐snow exchanges of HCHO can thus be explained without having to consider processes taking place in the quasi‐liquid layer present at the surface of ice crystals. A flux of HCHO to the atmosphere was observed simultaneously with an increase of HCHO concentration in snow, indicating photochemical production in surface snow. This study also suggests that the difference in bromine chemistry between Alert (Canadian Arctic) and Barrow leads to different snow composition and post‐deposition evolutions. The highly active bromine chemistry at Barrow probably leads to low HCHO concentrations at the altitude where diamond dust formed. Precipitated diamond dust was subsequently undersaturated with respect to thermodynamic equilibrium, which contrasts to what was observed elsewhere in previous studies.