Particulate organic nitrates observed in an oil and natural gas production region during wintertime
- 1Department of Chemistry, University of California, Berkeley, CA, USA
- 2Chemical Science Division, Earth System Research Laboratory, National Oceanic & Atmospheric Administration, Boulder, CO, USA
- 3Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA, USA
- 4Pacific Marine Environment Laboratory, National Oceanic & Atmospheric Administration, Seattle, WA, USA
- 5Department of Earth and Planetary Sciences, University of California, Berkeley, CA, USA
Abstract. Organic nitrates in both gas and condensed (aerosol) phases were measured during the Uintah Basin Winter Ozone Study from January to February in 2012. A high degree of correlation between total aerosol volume at diameters less than 500 nm and the particulate organic nitrate concentration indicates that organic nitrates are a consistent, if not dominant, fraction of fine aerosol mass. In contrast, a similar correlation with sub-2.5 μm aerosol volume is weaker. The C : N atomic ratio inferred from field measurements of PM2.5 and particulate organic nitrate is 34 : 1. Calculations constrained by the observations indicate that both condensation of gas-phase nitrates and heterogeneous reactions of NO3 / N2O5 are responsible for introducing organic nitrate functionality into the aerosol and that the source molecules are alkanes. Extrapolating the results to urban aerosol suggests organic nitrate production from alkanes may be a major secondary organic aerosol source.