Indoor Ultrafine Particle Aerosol Transformation Process Considering Coagulation Effect during Emission Period
SU-GWANG JEONG, Donghyun Rim,
Pennsylvania State University Abstract Number: 247
Working Group: Indoor Aerosols
AbstractIndoor ultrafine particles (UFP, <100 nm) are mainly originated form occupant activities, such as cooking and using consumer products. Human exposure to UFP can pose various environmental risks on human health such as DNA damage and oxidative stress. Indoor UFP exposure can significantly vary with emission source and aerosol transformation processes such as coagulation, deposition and ventilation. Such aerosol processes are affected by time-varying particle number concentration and size distribution specific to a source activity. This study investigated the particle transformation processes associated with episodic indoor source events by combining an analytical aerosol dynamic model and experimental data collected from full-scale residential buildings. The results show the size-resolved particle number concentration and geometric mean diameter (GMD) dramatically change with time for emission sources that release a number of small particles (< 20 nm). As a result, during the emission, particle number concentration increased in the form of a lognormal distribution, but the GMD also increased with time. This trend indicates that the effect of coagulation on the particle number concentration and size is significant even during the emission period. In addition, first-order equivalent coagulation loss rates were also higher at high particle number concentration (candle, gas stove), and these results show that both particle number concentration and size distribution have notable effects on coagulation dynamics during the emission period. The relative contributions of particle transformation processes (i.e., coagulation, deposition and ventilation) dynamically changes over the source emission and decay periods. Such aerosol loss mechanisms can meaningfully influence indoor particle size distribution, and accordingly human exposure to UFP in residences.