Size resolved particle emission rates from an evolving indoor aerosol system
J. Koivisto, M. Yu, K. Hämeri, M. Seipenbusch
Journal of Aerosol Science, 2012, Volume 47, May 2012, 58-69
Particle emission sources were characterized by evaluating aerosol data from an evolving aerosol with a mathematical model for indoor aerosols. The model incorporates ventilation, particle emission sources, coagulation, and deposition. The size-resolved particle emission rates were solved from the mathematical difference between measured and modeled concentration values. Particle sources were parameterized with log-normal particle emission rate distributions that were used for modeling input parameters. A series of particle emission tests in an emission chamber with a nanoparticle source, or both nanoparticle source and background particle source were conducted. The emission chamber particle deposition velocity was defined with a novel averaging method and with least square approximation. The size-resolved emission rates of the sources were defined by direct measurements and then solved with modelings from the emission chamber measurements. We developed iterative coagulation method which estimates particle coagulation in between the measurement time intervals. For two particle sources, a coupled particle general dynamic equation was developed. The study shows that the indoor aerosol model was capable of reconstructing the size-resolved particle emission rates of known sources, and to predict the sources influence on particle concentration levels with acceptable accuracy when the aerosol is fully mixed. We have shown that indoor aerosol modelings can be used for risk management of airborne particles by characterizing particle emitters and by estimating their influence on indoor concentrations.