Laboratory studies of the optical properties of warming aerosols with the SP2 and photoacoustic spectrometer: soot and hematite
Poster PDF
Authors
Manvendra K. Dubey — Los Alamos National Laboratory
Bradley Flowers — Los Alamos National Laboratory
Allison C Aiken — Los Alamos National Laboratory
Category
Aerosol Properties
Description
Most aerosols cool the atmosphere by scattering radiation. Absorbing aerosols, such as black carbon (BC) from combustion and hematite in dust, absorb radiation, resulting in a warming of the atmosphere. It is currently thought that BC is the second most important factor in global warming behind carbon dioxide, while dust is one of the major components of ambient aerosols globally. Direct online measurements of BC and hematite, an absorbing dust aerosol, can be made with the single-particle soot photometer (SP2), which measures the size and mass of the particles by incandescence and scattering on an individual particle basis. Measurements from the SP2 are combined with absorption measurements from the three-wavelength photoacoustic soot spectrometer (PASS-3) at 405, 532, and 781 nm and the ultraviolet photoacoustic soot spectrometer (PASS-UV) at 375 nm in order to determine wavelength-dependent mass absorption cross sections (MACs). Aerosols are generated by atomizing particles from aqueous solution, dried with a diffusion drier, and can be size-selected with a diffusion mobility analyzer (DMA) before being sent simultaneously to the SP2, PASS-3, PASS-UV, and a laser aerosol spectrometer (LAS) for measuring size distributions. Aerosol samples include flame-generated soot, fullerene soot, Aquadag, glassy carbon, and hematite. MACs from the absorbing aerosols measured in the laboratory are compared with those from ambient aerosols. Size-resolved information with bulk spectroscopic data is used to predict optical properties and is compared with our ambient observations for closure.
