Studies of the Role of Sea Ice in Arctic Tropospheric Ozone Chemistry

[9818257shepson]本项目主要研究大气化学对对流层臭氧产生和去除的影响。臭氧是大气的必要组成部分，有助于调节其氧化和去除潜在有害污染物的能力，但对人类呼吸系统和植被也是有毒的。因此，在对流层中一定存在着相当微妙的臭氧平衡。然而，在过去的一个世纪里，臭氧似乎大大增加了。这一点令人担忧，不仅因为臭氧有毒，而且因为它是一种重要的“温室”气体。该项目将调查令人惊讶的观测结果，即在极地日出时，北极海洋边界层中的臭氧完全消失。这一观察指出，我们目前对对流层臭氧的了解是相当不完整的。研究人员最近获得的证据表明，这一过程可能是由北冰洋冰/积雪中的卤化物离子氧化引起的，产生分子卤素（Br2和Cl2），然后挥发到大气中。然后，它们光解引发自由基链机制，从而破坏地表附近的臭氧。在1998年极地日出实验期间，获得了令人震惊的证据，证明甲醛（HCHO）在雪堆中产生光化学反应，然后挥发，这一过程是北极日出时海洋边界层中HCHO含量相对较高的原因。这一点非常重要，因为在相对干燥的极地大气中，HCHO光解反应是自由基最重要的来源之一。该项目将详细研究一种假设，即在北极日出时活跃发生的大部分气相光化学是在空气/雪/冰界面开始的。要做到这一点，有必要在西北偏西的阿勒特附近的北冰洋表面建立一个冰营，这是“极地日出实验2000”的关键组成部分。该项目将在2000年冬/春的2月初（持续黑暗）至4月（持续阳光）期间对关键的活性微量气体进行测量，并测量这些气体从地表的通量。在研究空气/雪/冰界面光化学的作用及其对重要对流层气体（如HCHO和O3）的影响的过程中，该项目迈出了令人兴奋的第一步。这项工作也直接关系到我们对雪表面化学和物理对冰芯浓度的作用以及相关历史的理解

ABSTRACT9818257ShepsonThis project is focused on studies of the atmospheric chemistry of tropospheric ozone production and removal. Ozone is both a necessary component of the atmosphere that helps regulate its' ability to oxidize and remove potentially hazardous pollutants, but is also toxic to the human respiratory system and to vegetation. Thus there must be a reasonably delicate balance of ozone in the troposphere. However, it appears that ozone has increased significantly over the past century. This is of concern not only because ozone is toxic, but also because it is an important "greenhouse" gas.This project will investigate the surprising observation that at polar sunrise, ozone is completely removed in the Arctic marine boundary layer. This observation points out that our current understanding of tropospheric ozone is quite incomplete. Researcher have recently obtained evidence that this process may be initiated by oxidation of halide ions in the Arctic Ocean ice/snow pack, to produce molecular halogens (Br2 and Cl2) that then volatilize into the atmosphere. They then photolyze to initiate a free radical chain mechanism that results in destruction of ozone near the surface. During the Polar Sunrise Experiment 1998, striking evidence was obtained that formaldehyde (HCHO) is produced photochemically in the snow pack, and then volatilizes, and that this process is responsible for the relatively high levels of HCHO in the marine boundary layer at sunrise in the Arctic. This is quite important, as HCHO photolysis represents one of the most important sources of free radicals in the relatively dry polar atmosphere. This project will pursue in detail the hypothesis that much of the gas phase photochemistry that occurs actively at sunrise in the Arctic is initiated at the air/snow/ice interface. To do this, it is necessary to set up an ice camp on the Arctic Ocean surface, near Alert, N.W.T., as a key component of the Polar Sunrise Experiment 2000. This project will conduct measurements of key reactive trace gases, and measure the fluxes of these gases from the surface, over a period covering early February (continuous darkness) through April (continuous sunlight) in the winter/spring of 2000. This project represents an exciting first step in the process of examining the role of air/snow/ice interfacial photochemistry and its impact on important tropospheric gases such as HCHO and O3. This work also ties directly to efforts to improve our understanding of the role of snow surface chemistry and physics on ice core concentrations and the associated historical