Impact of combined iodine and bromine release on the Arctic atmosphere (COBRA).

碘和溴混合释放对北极大气的影响 (COBRA)。

• 批准号: NE/D006015/1
• 负责人: Lucy Carpenter
• 金额: $ 17.5万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD006015%2F1
• 关键词: Impact; combined; iodine; bromine; release

Polar sunrise ozone and mercury depletion events are yearly phenomena that occur throughout the Arctic and Antarctic coastal regions, and have implications for the atmospheric oxidative capacity, climate and health. These events are believed to be caused by oxidation of ozone and mercury by bromine-containing radicals formed from photolysis of inorganic bromine (Br2, BrCl) released from the sea-ice surface. Recent studies suggest that 'frost flowers' (FF) - ice crystals that grow on newly formed sea ice - may be the dominant source of polar bromine. The exact nature of emissions from frost flowers is not well established and so far there are no field studies to confirm or otherwise the important role of FF in bromine release, compared to sea salt on sea-ice/snow-pack. Further, little is known about the role and sources of iodine in polar boundary layer chemistry. Iodine-containing aerosol has been associated with ozone depletion at polar sunrise but also appears in autumn - this is not consistent with the only known source of Arctic iodine, the under-ice spring bloom of ice algae. COBRA investigators have recently observed iodine oxide radicals in Antarctica and reactive organic iodine compounds in the Arctic. These so far unpublished observations, in separate polar locations, suggest a widespread and likely abiotic/photochemical source of iodine to the polar atmosphere. Recent theoretical studies indicate that iodine compounds emitted to the Arctic atmosphere have a significantly greater ozone and mercury depletion effect than additional bromine molecules, so our observations may be significant for polar halogen chemistry research. COBRA (Impact of combined iodine and bromine release on the Arctic atmosphere) is essentially a targeted process study, combining field, laboratory and modelling techniques in a consortium of scientists with strong track records in halogen and polar chemistry and physics to: develop understanding of the role of iodine (in concert with bromine) in Arctic gas phase photochemistry and aerosol production and evolution; investigate the relative/combined roles of frost flowers, older sea-ice/snow pack, sea salt aerosol and biological sources in releasing halogens to the Arctic atmosphere; increase understanding of the temporal and spatial variability of halogen-related ozone and mercury depletion events in the Arctic; and develop and evaluate parameterisations for emission of halogens to the Arctic atmosphere based upon observable ice and meteorological conditions, and use these to develop improved models of Arctic chemistry and emissions and their effect and feedbacks on regional/global atmospheric chemistry and climate. We will undertake two ground-based field campaigns, deploying a range of trace gas and aerosol techniques to measure inorganic and halogen compounds and a comprehensive suite of supporting data, in spring and autumn at a coastal site in the north of Hudson Bay, an area with high potential for frost flower growth and a bromine 'hot spot'. The autumn campaign will be augmented by ship-based measurements to determine the wider extent of mercury and ozone depletion episodes and organic halogen concentrations in the region. In addition to concentration measurements at the coastal site, we will measure particle, ozone and halogen concentrations and fluxes from frost flowers formed on artificial leads created in the sea-ice, and from older sea-ice/snow pack and any identified surface diatoms. We will characterise the various sea-ice surfaces in the field and investigate chemical mechanisms of formation from frost flowers in the laboratory. The combined impact of various forms of halogens on depletion of ozone and mercury will be investigated using a detailed process model, and on a wider scale using a global chemistry-transport model.

极地日出臭氧和汞消耗事件是整个北极和南极沿海地区每年都会发生的现象，对大气氧化能力、气候和健康产生影响。这些事件被认为是由海冰表面释放的无机溴（Br2、BrCl）光解形成的含溴自由基氧化臭氧和汞引起的。最近的研究表明，“霜花”（FF）——在新形成的海冰上生长的冰晶——可能是极地溴的主要来源。霜花排放的确切性质尚未明确，到目前为止，还没有现场研究来证实或与海冰/积雪上的海盐相比，FF 在溴释放中的重要作用。此外，人们对碘在极性边界层化学中的作用和来源知之甚少。含碘气溶胶与极地日出时的臭氧消耗有关，但也出现在秋季——这与北极碘的唯一已知来源——冰下春季冰藻的繁殖——不一致。 COBRA 研究人员最近在南极洲观察到了碘氧自由基，在北极观察到了活性有机碘化合物。这些迄今为止未发表的在不同极地地点的观测结果表明，极地大气中存在广泛且可能的非生物/光化学碘来源。最近的理论研究表明，排放到北极大气中的碘化合物比额外的溴分子具有显着更大的臭氧和汞消耗效应，因此我们的观察结果可能对极性卤素化学研究具有重要意义。 COBRA（碘和溴混合释放对北极大气的影响）本质上是一项有针对性的过程研究，由在卤素和极性化学和物理学方面拥有丰富记录的科学家组成的联盟将现场、实验室和建模技术相结合，以：碘（与溴一起）在北极气相光化学和气溶胶产生和演化中的作用；研究霜花、较旧的海冰/积雪、海盐气溶胶和生物源在向北极大气释放卤素方面的相对/综合作用；增进对北极与卤素相关的臭氧和汞消耗事件的时间和空间变化的了解；根据可观测的冰和气象条件，开发和评估向北极大气排放卤素的参数化，并利用这些参数开发北极化学和排放的改进模型及其对区域/全球大气化学和气候的影响和反馈。我们将在春季和秋季在哈德逊湾北部的沿海地点开展两次地面实地活动，部署一系列痕量气体和气溶胶技术来测量无机化合物和卤素化合物以及一套全面的支持数据。具有很高的霜花生长潜力和溴“热点”。秋季活动将通过船基测量得到加强，以确定该地区更广泛的汞和臭氧消耗事件以及有机卤素浓度。除了沿海地点的浓度测量外，我们还将测量颗粒、臭氧和卤素的浓度以及海冰中人造铅形成的霜花、较旧的海冰/积雪和任何已识别的表面硅藻的通量。我们将在现场描述各种海冰表面的特征，并在实验室中研究霜花形成的化学机制。将使用详细的过程模型来研究各种形式的卤素对臭氧和汞消耗的综合影响，并使用全球化学传输模型在更广泛的范围内进行研究。

项目成果

Particle fluxes and condensational uptake over sea ice during COBRA

COBRA 期间海冰上的粒子通量和凝结吸收

• DOI: http://dx.10.1029/2012jd017798
• 发表时间: 2012
• 期刊: Atmospheres
• 作者: Whitehead J

Energy and ozone fluxes over sea ice

海冰上的能量和臭氧通量

• DOI: http://dx.10.1016/j.atmosenv.2011.11.013
• 发表时间: 2012
• 期刊: Atmospheric Environment
• 影响因子: 5
• 作者: Muller J