Design and characterization of a smog chamber for studying gas-phase chemical mechanisms and aerosol formation

Abstract

We describe here characterization of a new state-of-the-art smog chamber facility for studying atmospheric gas-phase and aerosol chemistry. The chamber consists of a 30 m³ fluorinated ethylene propylene (FEP) Teflon film reactor housed in a temperature-controlled enclosure equipped with black lamps as the light source. Temperature can be set in the range from -10 to 40 °C at accuracy of ±1 °C as measured by eight temperature sensors inside the enclosure and one just inside the reactor. Matrix air can be purified with non-methane hydrocarbons (NMHCs) < 0.5 ppb, NO_x /O₃ /carbonyls < 1 ppb and particles < 1 cm^-3 . The photolysis rate of NO₂ is adjustable between 0 and 0.49 min^-1 . At 298 K under dry conditions, the average wall loss rates of NO, NO₂ and O₃ were measured to be 1.41 × 10^-4 min^-1 , 1.39 × 10^-4 min^-1 and 1.31 × 10^-4 min^-1 , respectively, and the particle number wall loss rate was measured to be 0.17 h^-1 . Auxiliary mechanisms of this chamber are determined and included in the Master Chemical Mechanism to evaluate and model propene-NO_x -air irradiation experiments. The results indicate that this new smog chamber can provide high-quality data for mechanism evaluation. Results of α-pinene dark ozonolysis experiments revealed secondary organic aerosol (SOA) yields comparable to those from other chamber studies, and the two-product model gives a good fit for the yield data obtained in this work. Characterization experiments demonstrate that our Guangzhou Institute of Geochemistry, Chinese Academy Sciences (GIG-CAS), smog chamber facility can be used to provide valuable data for gas-phase chemistry and secondary aerosol formation.

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