Three-wavelength measurement of aerosol absorption using a multi-resonator coupled photoacoustic spectrometer

Aerosol optical absorption measurements are important for the prediction of climate change, as aerosols directly disturb Earth's radiation balance by absorbing or scattering solar radiation. Although photoacoustic spectroscopy is commonly recognized as one of the best candidates to measure the absorption of aerosols, multi-wavelength measurements of aerosols optical absorption remain challenging. Here, a method based on photoacoustic spectroscopy that can simultaneously measure the aerosol absorption characteristics of three wavelengths (404, 637 and 805 nm) is proposed. In the three-wavelength photoacoustic spectrometer (TW-PAS), a photoacoustic cell with three acoustic resonators operating at different resonant frequencies was designed for offering multi-laser (multi-wavelength) operation simultaneously, and only one microphone was used to measure the acoustic signals of all resonators. The performance of TW-PAS was demonstrated and evaluated by measuring and analyzing the wavelength-dependent absorption coefficients of carbonaceous aerosols, which shows good agreement with previously reported results. The developed TW-PAS exhibits high potential for classifying and quantifying different types of light-absorbing aerosols by analyzing its absorption wavelength dependence characteristics.