Construction and Characterization of an Atmospheric Simulation Smog Chamber

Currently, air pollution in Beijing has become a complex problem with two types of source pollutants： coal smoke and photochemical smog. Furthermore the maximum hourly mean concentration of O3 increases continuously, especially in the summer. In order to simulate the photochemical reaction, develop an air quality simulation model and further improve the air quality of Beijing, a precisely temperature-controlled, indoor, smog chamber facility was designed and constructed at Tsinghua University. Characterization experiments have been carried out to acquire the basic parameters of the smog chamber, such as the wall loss rates of NO2, NO, O3, C3H6 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 results. The results indicate that the facility performs up to specifications, and can meet the demands required for simulating the photochemical reaction. The effect of high primary contaminated PM on the formation of ozone and secondary organic aerosol （SOA） is under investigation.

A large-scale outdoor atmospheric simulation smog chamber for studying atmospheric photochemical processes:Characterization and preliminary application

Understanding the formation mechanisms of secondary air pollution is very important for the formulation of air pollution control countermeasures in China.Thus,a large-scale outdoor atmospheric simulation smog chamber was constructed at Chinese Research Academy of Environmental Sciences(the CRAES Chamber),which was designed for simulating the atmospheric photochemical processes under the conditions close to the real atmospheric environment.The chamber consisted of a 56-m^(3) fluorinated ethylene propylene(FEP) Teflon film reactor,an electrically-driven stainless steel alloy shield,an auxiliary system,and multiple detection instrumentations.By performing a series of characterization experiments,we obtained basic parameters of the CRAES chamber,such as the mixing ability,the background reactivity,and the wall loss rates of gaseous compounds(propene,NO,NO_(2),ozone) and aerosols(ammonium sulfate).Oxidation experiments were also performed to study the formation of ozone and secondary organic aerosol(SOA),including α-pinene ozonolysis,propene and 1,3,5-trimethylbenzene photooxidation.Temperature and seed effects on the vapor wall loss and SOA yields were obtained in this work:higher temperature and the presence of seed could reduce the vapor wall loss;SOA yield was found to depend inversely on temperature,and the presence of seed could increase SOA yield.The seed was suggested to be used in the chamber to reduce the interaction between the gas phase and chamber walls.The results above showed that the CRAES chamber was reliable and could meet the demands for investigating tropospheric chemistry.