Wednesday, April 9, 2014
Environmental Science and Engineering Seminar
In situ constraints on reactive nitrogen cycling at atmospheric interfaces
Timothy Bertram, Assistant Professor, Department of Chemistry and Biochemistry, UC San Diego
Reactions occurring at atmospheric, aqueous interfaces can serve to catalyze reaction pathways that are energetically unfavorable in the gas phase. The reactive uptake of N2O5, a primary nocturnal nitrogen oxide (NOx) reservoir, serves as both an efficient NOx removal mechanism and regionally significant halogen activation process through the production of photo-labile ClNO2. Both the reaction rate and ClNO2 product yield are a complex function of the chemical composition of the reactive surface. To date, analysis of the impact of N2O5 chemistry on oxidant loadings in the marine boundary layer has been limited to reactions occurring on aerosol particles, with little attention paid to reactions occurring at the air-sea interface. Here, we report the first direct measurements of the air-sea flux of N2O5 and ClNO2 made via eddy covariance in the polluted marine boundary layer. The results are combined with in situ determinations of the N2O5 loss rates to aerosol particles and interpreted within a time-dependent coupled atmosphere-ocean model.