Measurement of Wavelength-Resolved Light Absorption by Aerosols Utilizing a UV-VIS Extinction Cell

摘要

The principle, technical details, and performance of the long\udpath extinction spectrometer (LOPES), a new folded-path extinction\udcell with a spectral range from the mid-UV (200 nm) to the\udnear infrared (1015 nm), is presented. Using nonabsorbing glass\udbeads the measured extinction spectrum of LOPES was validated\udby Mie calculations and was compared with scattering coefficients\udin the visible measured by a three-color integrating nephelometer\ud(TSI, mod. 3563). For absorbing aerosols (here soot and biomass\udburning aerosol with single-scattering albedos of about 0.2 and\ud0.74 at 550 nm), LOPES was combined with a TSI 3563 nephelometer\udto determine the wavelength-dependent absorption coefficients\udfrom the difference of the extinction and scattering coefficients.\udThese absorption coefficients were found to agree with the measurements by two state-of-the-art absorption techniques, the multiangle absorption photometry (MAAP) and photoacoustic spectrometry (PAS), which measure the absorption coefficient at the single wavelength of 532 nm and 670 nm, respectively. Finally, based on a comprehensive analysis of the TSI 3563 nephelometer errors and their propagation into the determination of the absorption coefficients from the LOPES and nephelometer data, we discuss implications for improving in situmeasurements of the optical properties of atmospheric aerosols.