Studies of the Production of Molecular Halogens in Arctic Snowpacks and on Sea Ice Surfaces

该项目将涉及在亚肯色州巴罗的实地实验，旨在提高对海盐卤化物、氯化物和溴化物氧化成分子卤素Cl2、BrCl2和Br2的了解。在北极的春季，有一个戏剧性的现象，其特征是大气最低层的臭氧完全消失，同时大气中的元素汞几乎完全消失。元素汞被氧化成短暂的产物，然后沉积到表面，在那里它可以进入并破坏敏感的生态系统。众所周知，这些臭氧消耗事件(ODE)和汞消耗事件(MDE)是由卤素原子化学引起的。然而，导致ODE和MDE的卤素反应的细节仍然未知，这限制了开发描述这些过程的模型的能力，以及它们未来可能如何变化。人们认为，释放分子卤素的过程与季节性或第一年(相对较薄和相对盐分)的海冰的存在有关。北极目前正在经历多年海冰范围的迅速减少，而第一年的海冰范围也随之增加。因此，研究人员假设，这种卤素化学以及与之相关的对大气组成和汞沉积的潜在影响，将增加到目前海冰消失的趋势继续下去的程度。为了更好地了解与北极分子卤素产生有关的基本过程，研究人员提出了一项实验，涉及在雪室中将天然雪样本和切除的海冰样本暴露于可能重要的大气氧化剂，并测量产物分子卤素。调查员还将同时测量天然积雪中这些化合物的浓度。然后，他将构建与ODE和MDES有关的详细化学光化学模型，然后将其纳入更大规模的地球系统气候和化学模型，以帮助可靠地模拟北极大气的未来状态。该项目将支持一名博士后研究员和一名研究生。将通过普渡气候变化研究中心、与巴罗当地社区的互动、对学校的访问以及通过在arcticstories.net网站上与冒险和儿童图书作家彼得·劳里合作，为许多外联活动提供支助。

This project would involve field experiments at Barrow, AK, aimed at improving understanding of the oxidation of the sea salt halides, chloride and bromide, into the molecular halogens, Cl2, BrCl, and Br2. In the Arctic at spring time there is a dramatic phenomenon characterized by the complete loss of ozone from the lowest layer of the atmosphere, along with near-complete loss of atmospheric elemental mercury. The elemental mercury is oxidized to short-lived products that then deposit to the surface, where it can enter and damage sensitive ecosystems. These ozone depletion episodes (ODEs) and mercury depletion episodes (MDEs) are known to occur as a result of halogen atom chemistry. However, the details of the halogen reactions that lead to the ODEs and MDEs are still unknown, limiting the ability to develop models that describe these processes, and how they might change in the future. It is thought that the processes that release molecular halogens are related to the presence of seasonal, or first-year (relatively thin and relatively saline), sea ice. The Arctic is currently experiencing a rapid decrease in the extent of multi-year sea ice, with associated increases in the extent of first-year sea ice. Thus the investigator hypothesizes that this halogen chemistry, and the associated potential impacts on atmospheric composition and deposition of mercury, will increase to the extent that the current trend in sea ice loss continues. To improve understanding of the fundamental processes associated with the production of molecular halogens in the Arctic, the investigator proposes an experiment involving exposures of natural snow samples and excised sea-ice samples in a snow chamber to potentially important atmospheric oxidants and measurement of the product molecular halogens. The investigator would also simultaneously conduct measurements of the concentrations of these compounds within the natural snowpack. He would then construct a detailed photochemical model of the chemistry involved with ODEs and MDEs, that could then be incorporated into larger scale Earth System climate and chemistry models to help enable reliable simulations of the future state of the Arctic atmosphere. The project would support a postdoctoral researcher and a graduate student. Numerous outreach activities would be supported through the Purdue Climate Change Research Center, interactions with the local community in Barrow, visits to schools, and through collaboration with adventure and children's book writer Peter Lourie on the web site arcticstories.net.