Detection of Inorganic Dihalogen Gases (Cl2, Br2, I2, BrCl, and ICl) in the Marine Atmosphere

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This award supports field measurements of several dihalogen compounds, Cl2 (molecular chlorine), Br2 (molecular bromine), I2 (molecular iodine), BrCl (bromine chloride), and ICl (iodine chloride) in coastal and marine air. The measurements will be made using atmospheric pressure chemical ionization tandem mass spectrometry (APCI/MS/MS) in the negative ion spectrum. Laboratory tests and preliminary field measurements of Cl2 and I2 in ambient coastal air indicate that this technique is capable of low pptv detection limits. The goals of this project are (1) to validate and further develop the analytical method for dihalogens in air, (2) to explore the distribution of these gases in coastal and remote marine air, and (3) to test various hypotheses regarding the origin and impact of halogen chemistry in marine air. Field measurements are planned for Malibu, CA, the Scripps pier, and Bermuda. This research is important because halogen compounds play a critical role in stratospheric chemistry, but also in the troposphere, where they can release halogen atoms that can destroy ozone and act as oxidants and affect the lifetimes of unsaturated hydrocarbons and alter reaction pathways for reduced sulfur gases. To date, there are few direct measurements of these reactive halogen compounds in the marine troposphere. This project will support a graduate student as well as undergraduate students. It will also contribute to the training of an Earth Sciences high school teacher.