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

University Of California-Davis, Davis CA

Investigators

Abstract

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.