RUI: Chemical Characterization and Reactivity of Chromophoric Dissolved Organic Matter (CDOM) in Rainwater

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This project addresses the questions: (1) What are the origin and chemical characteristics of chromophoric dissolved organic matter (CDOM) in rainwater? (2) What is CDOM's role in photochemical transformations? (3) What is CDOM's involvement in metal speciation? These questions will be studied with a variety of tools including isotopic analysis, NMR, and controlled photolysis experiments. For the analyses, rainwater CDOM samples will be collected during different seasons, storm types, and locations. The rates and quantum yields for the formation of hydrogen peroxide and other small molecules will be determined with photolysis experiments. The contribution of CDOM nitrogen to dissolved organic nitrogen in rainwater will also be assessed. This research will provide new information on the chemical and physical factors influencing sources, fate, and atmospheric impacts of rainwater CDOM, which may be the predominant form of carbon in precipitation. CDOM photochemistry affects the spectral attenuation of solar radiation, tropospheric free radical chemistry, oxidizing capacity, acid generating capacity, and trace metal speciation in the atmosphere. Broader impacts also include education and training of a post-doctoral researcher, two master's level graduate students, two undergraduates and one high school student each year. In addition, a local high school science teacher will participate in this research for one month each year.