Construction and characterization of an indoor smog chamber for measuring the optical and physicochemical properties of aging biomass burning aerosols

We describe here the construction and characterization of a new combustion-chamber system (the NCAT chamber) for studying the optical and physicochemical properties of biomass burning (BB) aerosols. This system is composed of a ~9 m ³ fluorinated ethylene propylene (FEP) film reactor placed in a temperature-controlled room that uses a tube furnace to combust biomass fuel samples under controlled conditions. The optical properties are measured using a cavity ring-down spectrometer and nephelometer. Aerosol number density and size classification used condensation particle counter, and differential mobility analyzer. Other analytical instruments, used include NO _x , O ₃ , CO, and CO ₂ analyzers, a gas chromatograph, and particle filter samples for determining the physicochemical and morphological properties. The construction details and characterization experiments are described, including measurements of the BB particulate size distribution and deposition rate, gas wall loss rates, dilution rate, light intensity, mixing speed, temperature and humidity variations, and air purification method. The wall loss rates for NO, NO ₂ , and O ₃ were found to be (7.40 ± 0.01) × 10 ^–4 , (3.47 ± 0.01) × 10 ^–4 , and (5.90 ± 0.08) × 10 ^–4 min ^–1 , respectively. The NO ₂ photolysis rate constant was 0.165 ± 0.005 min ^–1 , which corresponds to a flux of (7.72 ± 0.25) × 10 ¹⁷ photons nm cm ^–2 s ^–1 for 296.0–516.8 nm, and the particle deposition rate was (9.46 ± 0.18) × 10 ^–3 min ^–1 for 100 nm mobility diameter BB particles from pine. Preliminary results of the single scattering albedo of fresh and aged BB aerosols are also reported.