Measuring Optical Properties of SOOT from Biomass Burning Using Cavity RING-DOWN Spectroscopy and Integrating Nephelometry
Friday, 19 December 2014
Since black carbon and brown carbon are among the greatest contributors to radiative forcing (black carbon being second only to carbon dioxide), this work focuses on the laboratory measurement of their optical properties using cavity ring-down spectroscopy (CRDS) and integrating nephelometry. Water soluble soot is collected using an impinger by burning different fuel types to mimic ambient aerosols dominant in regions where biomass burning is the main source of aerosols. Using an optical parametric oscillator (OPO) as a light source, we are able to measure extinction and scattering over a wide range of wavelengths. The extinction-minus-scattering method is then used to determine particle absorption and single scattering albedo for soot collected from different fuel sources at different stages of burning. Purely scattering polystyrene latex (PSL) spheres of known sizes (100 – 700 nm) are used in the lab to calibrate the system for this study. Our preliminary measurements of optical properties of soot samples collected by burning different wood samples will be reported. A correction method that properly accounts for and reduces systematic extinction uncertainties, random scattering and extinction errors, and reconciles nephelometer with CRDS measurements is used.