Chemical coupling between ammonia, acid gases, and fine particles

The concentrations of inorganic aerosol components in the fine particulate matter (PM(fine)less than or equal to2.5 mum) consisted of primarily ammonium, sodium, sulfate, nitrate, and chloride are related to the transfer time scale between gas to particle phase, which is a function of the ambient temperature, relative humidity, and their gas phase constituent concentrations in the atmosphere. This study involved understanding the magnitude of major ammonia sources; and an up-wind and down-wind (receptor) ammonia, acid gases, and fine particulate measurements; with a view to accretion gas-to-particle conversion (GTPS) process in an agricultural/ rural environment. The observational based analysis of ammonia, acid gases, and fine particles by annular denuder system (ADS) coupled with a Gaussian dispersion model provided the mean pseudo-first-order k(s-1) between NH3 and H2SO4 aerosol similar to5.00 (+/-3.77) x 10(-3) s(-1). The rate constant was found to increase as ambient temperature, wind speed, and solar radiation increases, and decreases with increasing relative humidity. The observed [NH3][HNO3] products exceeded values predicted by theoretical equilibrium constants, due to a local excess of ammonia concentration. (C) 2003 Elsevier Ltd. All rights reserved.