Title: Observation based analysis for the determination of equilibrium time constant between ammonia, acid gases, and fine particles

Authors: Bok Haeng Baek, Viney P. Aneja

Addresses: Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA. ' Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA

Abstract: Experimental measurements of ammonia, acid gases, and the inorganic components of atmospheric aerosols were made at a commercial hog farm in eastern North Carolina from May 1998 to June 1999 by an annular denuder system (ADS). The ADS consisted of a cyclone separator, one diffusion denuder coated with sodium carbonate, another diffusion denuder with citric acid, and a filter pack containing Teflon and nylon filters in series. The equilibrium time constant for transfer between ammonia, acid gases, and aerosol phase of ammonium nitrate and ammonium chloride was determined based on kinetic rate constants (k_N as the rate constant of ammonium nitrate aerosol: 2.04 × 10^-4 m³/µmole/sec; k_Cl as the rate constant of ammonium chloride aerosol: 3.44 × 10^-4 m³/µmole/sec) and the observed inorganic components of atmospheric aerosols. The equilibrium time constant was determined based on kinetic rate constants and the observed inorganic components of atmospheric aerosols. The equilibrium time constant has a wide range of values, with an average value of 15.26 (±10.94) minutes for ambient equilibrium time between ammonia, nitric acid gas and ammonium nitrate aerosol; and 8.22 (±6.81) minutes for ammonia, hydrochloric acid, and ammonium chloride. Significant correlations were determined between comparisons of equilibrium time constant estimates with meteorological parameters, such as ambient temperature and relative humidity. The predicted chemical compositions in the particle by EQUISOLV II Model are in good agreement with the observed chemical composition at the experimental site.

Keywords: equilibrium time constant; ammonia; ammonium nitrate; ammonium chloride; gas-to-particle conversion; acid gases; fine particles; atmospheric aerosols; commercial hog farms; hydrochloric acid; atmospheric particles; meterological factors.

DOI: 10.1504/IJEP.2005.006864

International Journal of Environment and Pollution, 2005 Vol.23 No.3, pp.239 - 247

Published online: 19 Apr 2005 *

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