The \(H_2SO_4-HNO_3-NH_3\) system at high humidities and in fogs: 2. Comparison of field data with thermodynamic calculations

Abstract

Concentrations of HNO(g) and NH(g) determined in the field were compared to predictions from aerosol equilibrium models. The products of HNO(g) and NH(g) concentrations measured under cool and humid nonfoggy conditions agreed in magnitude with predictions from a comprehensive thermodynamic model for the atmospheric HSO‐HNO‐NH‐HO system. Observed concentrations of NH(g) in fogs were generally consistent with those predicted at equilibrium with fog water, but important discrepancies were noted in some cases. These discrepancies may be due to fluctuations in fog water composition over the course of sample collection or to the sampling of nonfoggy pockets of air present within the fog. Detectable concentrations of HNO(g) (up to 23 neq m) were often found in fogs with H 5 were below the detection limit of 4–8 neq m.