Photochemical Formation of Oxidants and Destruction of Organic Compounds in the Snowpack at Summit, Greenland

最近的研究表明，极地积雪中的光化学反应可以显著影响积雪及其上覆大气的化学成分和组成。有机分子的光化学是重要的，因为它们在极地地区的毒性作用，它们在积雪和冰芯中作为来源标记的潜在重要性，以及它们对挥发性有机化合物向大气释放的光化学贡献。尽管这很重要，但人们对特定有机化合物在雪或冰上的反应知之甚少。人们对有机化合物在冰上的直接光解作用进行了一些研究，但对它们的间接反应，即与光形成的氧化剂（如羟基自由基）的反应几乎一无所知。这是我们知识上的一个重大空白，因为这些氧化剂可能主导了雪中大多数有机物的破坏。我们在这一领域缺乏知识，因此很难预测雪相有机物的反应或寿命，以及这些反应如何影响极地问题。目标是结合实地和实验室工作，以确定在格陵兰峰顶的雪上形成活性氧化剂的速率和机制，以及有机化合物的衰变。首席研究员试图确定温度和pH值等环境变量对这种化学反应的影响有多重要，最终目标是估计积雪中各种有机化合物的寿命。首席研究员将使用他在过去两个季节开发的湿/冷冻化学技术测量积雪中氧化剂的浓度。他将在山顶的雪上测量一组模型有机化合物的寿命和衰变。将这些测量的寿命与基于氧化剂测量计算的值进行比较，将表明是否存在额外的、缺失的有机物破坏机制。然后，他将在实验室中对经过处理的Summit样品进行一系列光化学实验，以更清楚地了解氧化剂形成和有机化合物破坏的机制。最后一个组成部分将是结合现场和实验室数据，以估计各种地点的雪中各种有机化合物的寿命。更广泛的影响：将培养2名本科生、1名博士生和1名研究生，研究成果将在科学期刊上发表。将与当地一名中学教师和她的九年级科学班合作，开发一个关于全球气候变化和北极的三到五天的单元，其中包括在峰会上讨论首席研究员的经验和研究。每堂课，都会有一名前往Summit的学生协助准备和分发教材。最后，他将把这个研究项目的结果整合到一门关于空气质量的本科课程中，让学生们了解极地地区面临的重要问题。

Recent research has shown that photochemical reactions in polar snowpacks can significantly affect the chemistry and composition of the snowpack and the overlying atmosphere. The photochemistry of organic molecules are important because of their toxic effects in polar regions, their potential importance as source markers in snowpacks and ice cores, and their contribution to the photochemical release of volatile organic compounds to the atmosphere. Despite this importance, little is known about the reactions of specific organic compounds on snow or ice. There have been a few studies of the direct photolysis of organic compounds on ice, but almost nothing is known of their indirect reactions, i.e., with photoformed oxidants such as hydroxyl radical. This is a major gap in our knowledge because these oxidants probably dominate the destruction of most organics in snow. Our lack of knowledge in this area makes it very difficult to predict the reactions or lifetimes of snowphase organics and how these reactions affect the polar issues. The goal is to combine field and laboratory work to determine the rates and mechanisms for the formation of reactive oxidants, and decay of organic compounds, on snow at Summit, Greenland. The Principal Investigator seeks to determine how important environmental variables such as temperature and pH affect this chemistry, with a final goal of estimating the lifetimes of a wide range of organic compounds in snowpacks. The Principal Investigator will measure snowpack concentrations of oxidants using wet/frozen chemistry techniques that he developed over the past two seasons. He will measure the lifetimes and decay of a suite of model organic compounds on Summit snow. Comparing these measured lifetimes with values calculated based on oxidant measurements will indicate whether there are additional, missing mechanisms for the destruction of the organics. He will then perform a series of photochemistry experiments on manipulated Summit samples in the laboratory to more clearly understand the mechanisms for oxidant formation and organic compound destruction. The final component will be to combine the field and laboratory data to estimate the lifetimes of a wide range of organic compounds in snow at a variety of locations. Broader Impacts: Two undergraduate students, one doctoral student, and one postgraduate fellow will be trained and research results will be disseminated in scientific journals. There will be a collaboration with a local middle school teacher and her 9th grade science classes to develop a three to five day unit on global climate change and the Arctic which will include a discussion of the Principal Investigator's experiences and research at Summit. For each class, one of the students that traveled to Summit will assist in the preparation and delivery of the material. Finally, he will integrate results from this research project into an undergraduate class on air quality to expose the students to important issues facing polar regions.