Pilot Study of Photochemical Reaction under High PMContaminated Condition by Tsinghua Smog Chamber

摘要

Currently, the air pollution in Beijing has become a complex problem with two types of source pollutants: coal smoke and photochemical smog, and further the maximum hourly mean concentration of O_3 increases continuously especially in summer. In order to simulate the photochemical reaction and develop air quality simulation model, and further improve air quality of Beijing, a precisely temperature-controlled indoor smog chamber facility was designed and constructed in Tsinghua University. The characterization experiments have been carried out to acquire the basic parameters of the smog chamber, such as the wall loss rates of NO_2, NO, O_3, C_3H_6 and particulate matter (PM), the intensity of ultraviolet (UV) light in the chamber, the reactivity of the purified air and the reproducibility of the experimental result. The results indicate that the facility performs well, and can basically meet the demand of the photochemical reaction. The effect of ammonium sulfate aerosol on the photochemical reaction of toluene/Nox/air mixture was evaluated with this faxility. The results indicate that the presence of concentrated preexisting ammonium sulfate aerosol shortens the time to reach maximum PM concentration and increases the aerosol yield of toluene comparing with the presence of no preexisting aerosol. And under the presence of high concentrated ammonium sulfate aerosol seed, the concentration of aerosol does not have significant effects on Nox-NO and O_3 variation, but affects the formation of secondary organic aerosol (SOA). The SOA yield increases with the increasing initial ammonium sulfate seed concentration ( < 160 μg-m~(-3)).