An Intercomparison of Instruments Measuring Carbonaceous Aerosol Light Absorption

AUGUST LI, Rajan K. Chakrabarty, Washington University in St. Louis

     Abstract Number: 236
     Working Group: Instrumentation and Methods

Abstract
In this research, laboratory measurements of light absorption of fresh-emitted carbonaceous aerosol generated from biomass combustion, along with the aerosol mass concentration, were collected. The goal of this research is to compare the absorption measurements from three different instruments: a particle soot absorption photometer (PSAP) and a tricolor absorption photometer (TAP), and a photoacoustic spectrophotometer (PAS). PSAP and TAP are filter-based instruments that measure absorption at red, green, and blue regions on the visible spectra (the specific wavelengths for the two instruments are slightly different), whereas the PAS measure absorption at 405, 721, and 1047 nm wavelengths. Therefore, the absorption at different wavelengths needs to be adjusted for comparison. Preliminary results showed that absorption measurements from the PAS are mostly lower than those from the PSAP, with comparison slope ranges from 0.42 to 1.62. The single scattering albedos for the fresh biomass burning aerosol are 0.91–0.94 405 nm wavelength, 0.91–0.95 at 532 nm, and 0.90–0.95 at 660 nm. Future steps for this research include comparison of absorption measurements between the PAS and TAP, and between TAP and PSAP. The effects of mass concentration (collected by a scanning mobility particle sizer) on aerosol absorption measurements will also be taken into consideration by deriving the mass absorption coefficients (MAC) for the instruments at all wavelengths.