Analytical Chemistry Seminar: Veronica Vaida and Eleanor Browne
Analytical & Environmental Chemistry Division and Atmospheric Chemistry Program Seminar
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
Building molecular complexity with sunlight at aqueous interfaces
by Veronica Vaida - Professor, Department of Chemistry and Biochemistry & CIRES Fellow, University of Colorado Boulder
High energy, low entropy solar radiation can be used to initiate radical reactions leading to organic polymers and oligomers in environmental systems. In atmospheric chemistry, the role of the photochemically generated OH radical is well studied. However, the role of other radicals, especially those generated from organic precursors, is less well-understood. This presentation will discuss examples of photochemically-initiated organic radical reactions at the water surface. Specifically, the photochemistry of oxoacids, such as pyruvic acid as well as a series of oxoacids with longer aliphatic side chains, will be discussed. Photochemical processing occurs with solar simulators under both aerobic and anaerobic environments, characteristic of the contemporary and ancient Earth’s atmosphere, respectively. The polymers produced are investigated by mass spectrometry and NMR, while the supramolecular aggregates that spontaneously self-assemble during photolysis are monitored by microscopy and dynamic light scattering. Implications of these abiotic processes to atmospheric and environmental chemistry will be discussed, specifically as they affect aerosol nucleation and growth.
Atmospheric Reduced Nitrogen: Trends and Future Directions
by Eleanor Browne - Professor of Chemistry and Biochemistry & CIRES Fellow, University of Colorado Boulder
Organic nitrogen is a ubiquitous atmospheric component typically accounting for between one-quarter and one-third of reactive nitrogen deposition, however, its chemical complexity and its reactivity has made it challenging to study. Consequently, little is known about the atmospheric processing of organic nitrogen and the resulting implications for biogeochemistry, air quality, and climate. Organic nitrogen can be broadly separated into two groups: oxidized organic nitrogen compounds such as acyl peroxy nitrates and reduced organic nitrogen compounds such as amines. Historically, our knowledge of the chemistry of reduced organic nitrogen has lagged behind that of oxidized organic nitrogen due to the dominance of oxidized nitrogen sources. Recent enactment of air quality regulations in the United States and parts of Europe, however, has resulted in decreased emissions of oxidized nitrogen while emissions of reduced nitrogen have remained constant or have increased due to expansion of agriculture and increased use of fertilizer. Thus, it is timely to study the chemistry of reduced organic nitrogen. I will discuss trends in emissions of reduced nitrogen, its implications for reduced organic nitrogen, and future studies on the chemistry of reduced organic nitrogen.