Effect of different organic salts on ammonia volatilization in ammonium nitrate

Abstract

The ammonium salts and organic salts are the important components of atmospheric aerosols. The reaction between the two salts will cause the release of NH3, hence, affecting the budget of NH3 in the atmosphere. Furthermore, the equilibrium partitioning of NH3 in the gas and particle phases plays a key role in the evolution of chemical composition and size of fine atmospheric particles. In this work, the chemical composition evolution processes of mixed particles consisting of four different organic acid salts (sodium oxalate (SO), sodium malonate (SM), sodium succinate (SS), sodium pyruvate (SP)) with ammonium nitrate (AN) were measured by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The release of NH3 were gained by monitoring the changes in the absorbance of NH4 + in mixed organic acid salts/AN particles under 70% relative humidity (RH). After 127 minutes, the remaining ammonium content in the four mixed aerosols was 84.2%, 71.6%, 57.1%, and 28.7% for SO, SM, SS, and SP mixed with AN, respectively, which is lower than that in pure AN aerosol (97%). This study may help to further understand the conversion process between organic salts and AN in the atmosphere, as well as the NH3 cycles in the atmosphere.