Ambient PM2.5, Black Carbon, and Particle Size-Resolved Number Concentrations and the Angstrom Exponent Value of Aerosols during the Firework Display at the Lantern Festival in Southern Taiwan

摘要

The Yanshui Beehive Firework Festival is a traditional folk activity in Southern Taiwan held during the Lantern Festival, and it is the third largest folk celebration in the world. During this festival, more than 200 firecracker towers with hundreds of thousands of firecrackers are ignited, posing a risk to public health because of an abrupt increase in particulate matter concentrations within a short period. In this study, real-time variations of PM2.5 (particles with an aerodynamic diameter less than or equal to 2.5 mu m), black carbon (BC), and particle number concentrations were monitored before and during the firework display to understand the effect of the firework display on the short-term air quality. The hourly average concentrations of PM2.5, BC, total particle number, and ultrafine particle number during the firework display (episode period) were 146.9 mu g m(-3), 2639 ng m(-3), 3.37 x 10(4) # cm(-3), and 1.18 x 10(4) # cm(-3), respectively. These values were 6.9, 2.3, 5.9, and 3.7 times greater than those during the same period on reference days (nonepisode period), respectively. The measured ultraviolet BC (UVBC) and BC concentrations indicated that aerosols were bound with ultraviolet-absorbing organic compounds, which were abundant, during the episode period. BC aerosols during the episode originated from vehicular traffic and firecracker burning, and the absorption Angstrom exponent value was 1.4. The particle number size distribution during the episode period showed a major accumulation mode and a minor Aitken mode of 180 and 63 nm, respectively. This particle number size distribution pattern was considerably different from that in the nonepisode period. During the episode period, particle coagulation played a crucial role in removing particles in the nucleation and Aitken modes in the ambient air at high particle number concentrations.