A systematic re-evaluation of methods for quantification of bulk particle-phase organic nitrates using real-time aerosol mass spectrometry

Abstract. Organic nitrate (RONO2) formation in the atmosphere represents a sink of NOx (NOx = NO + NO2) and termination NOx/HOx (HOx HO2 OH) ozone radical propagation cycles, can act as reservoir transporting reactive nitrogen, contributes to secondary organic aerosol formation. While some fraction RONO2 is thought reside particle phase, particle-phase nitrates (pRONO2) are infrequently measured thus poorly understood. There an increasing prevalence mass spectrometer (AMS) instruments, which have shown promise for determining quantitative total functional group contribution aerosols. A simple approach that relies on relative intensities NO+ NO2+ ions AMS spectrum, calibrated NOx+ ratio NH4NO3, inferred pRONO2 has been proposed way apportion signal NH4NO3 pRONO2. This method increasingly being applied field laboratory data. However, methods largely inconsistent characterized, and, therefore, detailed evaluation timely. Here, we compile extensive survey ratios various compounds mixtures from multiple groups, measurements. All data analysis presented here use with standard vaporizer. We show that, absence standards, be estimated using referenced ratio, so-called “Ratio-of-Ratios” (RoR 2.75 ± 0.41). systematically explore basis quantifying (and NH4NO3) RoR ground aircraft measurements conducted over large range conditions. The compared another (positive matrix factorization, PMF) other related (e.g., gas RONO2) measurements, generally showing good agreement/correlation. broad shows pervasive trend higher fractional lower concentrations, corresponds shifts urban-influenced rural/remote regions. Compared campaigns, observations all campaigns showed substantially contributions at midranges (0.01–0.1 up 2–5 µg m−3), suggesting balance effects controlling lifetimes – such humidity, temperatures, greater dilution, different sources, acidity, hydrolysis (possibly accelerated by acidity) favors those environments altitudes sampled.