In-situ airborne measurements of nitrous acid in power plant and biomass burning plumes

Hydroxyl radicals formed from the photolysis of nitrous acid (HONO) can increase oxidation in the atmosphere. Recent advancements in HONO detection techniques have allowed HONO to be measured with sufficient accuracy and precision to assess its influence upon tropospheric chemistry. Airborne observations of HONO and other trace gases in the troposphere over the Southeastern US were performed from the NOAA WP-3D aircraft during the Southeast Nexus Experiment (SENEX 2013) in the summer of 2013. The aircraft flew during both day and night, and sampled primarily in the planetary boundary layer. Emissions and subsequent atmospheric chemistry from urban areas, power plants, and oil and gas extraction were studied. Using a chemical ionization mass spectrometer, HONO was measured once per second with a measurement precision of 10 pptv for 10 s averages. The largest observed HONO mixing ratios were in biomass burning plumes (up to several ppbv) and in fresh emissions from electrical generation power plants (up to several hundred pptv). The importance of these observations to understanding radical budgets will be discussed.