Kinetics of evaporation of ammonium chloride and ammonium nitrate aerosols

Fate of ammonia in the atmosphere?a review for applicability to hazardous releases

“…Attempts to build numerical models to account for the measured concentrations of NH3, HNO3, and NH4NO3 in the atmosphere have been largely unsuccessful [142] as were attempts to identify the rate-determining step in the mechanisms involved [143]. Nonetheless, a general understanding of the factors involved emerges from several other studies [144][145][146][147] allowing a qualitative explanation of the trends observed.…”

“…Nonetheless, a general understanding of the factors involved emerges from several other studies [144][145][146][147] allowing a qualitative explanation of the trends observed. Deviations from predicted values based on thermodynamics occur when not enough time is available for the system to reach equilibrium after a change in the concentration of one of the chemicals involved, or after a rapid change in atmospheric conditions particularly temperature and/or relative humidity.…”

“…Harrison et al [146] measured the evaporation rate of ammonium nitrate and chloride aerosols in an annular denuder where vapors of NH3, HC1, and HNO3 are rapidly and continuously removed. Rates were expressed in terms of the rate of decrease of particle diameter.…”

“…The first determinations of the mass accommodation coefficient for ammonia were made indirectly by measuring the evaporation rates of ammonium nitrate and of chloride from their aqueous solutions [18][19][20]. In the mathematical treatment of the experimental data, the mass accommodation coefficient is treated as an adjustable parameter, selected to fit the data.…”

“…Because of the high solubility of ammonia in water, they assumed that the mass transfer in the liquid will be much faster than the mass transfer in the gas phase and used the following approximate equation for KQ: (20), the time to reach equilibrium concentration of ammonia was computed for different droplet sizes.…”