Collaborative Research: Studies of Chlorine, Bromine and Iodine Chemistry in the Arctic, and its Impacts

该项目旨在提高我们对北极地区卤素（氯、溴和碘）化学影响的定量认识，以便更可靠地进行海冰和积雪条件未来变化对大气成分影响的模型模拟。在地球的非极地地区，大气通过涉及臭氧的光化学作用进行自我清洁，而海冰覆盖地区上空的大气至少部分通过涉及卤素原子（氯、溴和碘）的化学作用进行自我清洁。这种卤素化学有时表现为在低层大气中臭氧和元素汞的快速消耗（与大气中的其他部分相比，这是非常不寻常的），消耗到接近零的水平。臭氧是一种非常重要的大气成分，是一种强大的清洁剂，但它也对植物和人体呼吸系统有毒，是一种受管制的空气污染物。单质汞在氧化后可转化为剧毒形式，例如甲基汞。由于这种极地卤素化学是独特的，因此需要根据其全球影响以及北极发生的快速环境变化的背景来理解它。这笔赠款将资助一个合作小组，对阿拉斯加州巴罗的含盐积雪中Cl2、Br2和I2的通量（即排放率）进行测量。决定通量的控制环境变量（如阳光、臭氧的存在、pH值、盐浓度、雪成分）将通过雪室、在巴罗收集的各种雪和冰样本以及通过对巴罗附近积雪排放的直接测量进行研究。然后，该小组将使用测量到的卤素通量和垂直混合信息来约束一维（垂直尺度）数值模型，以研究地表通量的垂直尺度影响，并研究随着气候变化地表性质的变化，这种影响可能会如何变化。这项工作的一个重要发现部分将集中在分子碘和碘化学上，迄今为止，这方面在北极的探索很少。更广泛的影响是面向了解北极的目标，以便更好地预测北极变化的影响，以及北极变化对地球系统其他部分的影响。该项目的一个重点将是教育和激励下一代学者、教师和研究人员了解科学和不断变化的地球。三位首席研究员将在这个项目的过程中指导本科生和研究生。在巴罗参加实地考察的学生将获得在恶劣环境下进行实验、在偏远地区管理科学后勤以及与北极人民建立科学和教育伙伴关系等方面的独特经验。与这个项目合作的探险和自然作家彼得·劳里将写一本关于海冰的新书，包括科学家如何研究它，为什么它对人类和地球很重要，以及它是如何变化的。他还将制作关于北极海冰和科学的在线教材，目标受众是中学教育。所有参与的科学家都将参与一系列的外联活动，包括在学校做报告、参与“公众门户”——一个非正式科学教育努力的全国性网络——以及积极招募代表性不足的群体从事科学和教育事业。

This project aims to improve our quantitative understanding of the impact of halogen (chlorine, bromine, and iodine) chemistry in the Arctic, so that model simulations of the impact of future changes in sea ice and snowpack conditions on atmospheric composition can be more reliably conducted. While in non-polar regions of the planet the atmosphere cleans itself through photochemistry that involves ozone, the atmosphere above sea-ice covered regions cleans itself at least in part through chemistry involving halogen atoms - chlorine, bromine and iodine. This halogen chemistry sometimes manifests itself through the very rapid (and very unusual, compared to the rest of the atmosphere) consumption of ozone and elemental mercury, to near-zero levels, in the lower atmosphere. Ozone is a critically important atmospheric constituent that is a powerful cleaning agent, but it is also toxic to plants and to the human respiratory system, and is a regulated air pollutant. Elemental mercury, when oxidized, can be converted to highly toxic forms, e.g. methyl mercury. Since this polar halogen chemistry is unique, it needs to be understood in terms of its global impact, and in the context of the rapid environmental change occurring in the Arctic.The grant would fund a collaborative team to conduct measurements of fluxes (i.e. rates of emission) of Cl2, Br2, and I2, from the saline snowpack at Barrow, Alaska. The controlling environmental variables (e.g. sunlight, presence of ozone, pH, salt concentrations, snow composition) that determine the fluxes will be studied using a snow chamber, using a variety of snow and ice samples collected at Barrow, and through direct measurements of the emission from the snowpack near Barrow. The team will then use the measured halogen fluxes and vertical mixing information to constrain a one-dimensional (vertical scale) numerical model to investigate the vertical scale impact of the surface fluxes, and to examine how this might change as the nature of the surface changes with climate change. A significant part of the discovery component of the effort will focus on molecular iodine and iodine chemistry, which has been little-explored in the Arctic to date. The broader impacts are oriented toward the goal of understanding the Arctic in order to inform better prediction of the impacts of change in the Arctic, and of the impact of Arctic change on other parts of the Earth system. A focus of this project will be the education and inspiration of the next generation of scholars, teachers, and researchers about science and the changing planet. Each of the three lead investigators will mentor both undergraduate and graduate students in the course of this project. Students who participate in the field effort at Barrow benefit from a unique experience in conducting experiments in harsh environments, managing science logistics in remote locations, and engaging in science and education partnerships with Arctic people. In partnership with this project an adventure and nature writer, Peter Lourie, will write a new book about sea ice, how scientists study it, why it is important to humans and to the planet, and how it is changing. He will also produce on-line educational material about sea ice and science in the Arctic, aimed at middle-school education. All of the participating scientists will be engaged in a range of outreach activities, including presentations at schools, involvement with "Portal to the Public" - a nationwide network of informal science education efforts - and with the active recruitment of underrepresented groups to pursue careers in science and education.