Aerosol Absorption at High Relative Humidity - Does Absorption Enhancement Exist?

An aerosol albedometer has been combined with laser induced incandescence (LII) measurements to determine mass absorption cross section (MAC) of light absorbing soot particles in real-time. Laboratory results suggest an enhancement of light absorption occurs when soot becomes internally mixed or coated, in agreement with the work of previous authors. Coatings of ammonium sulfate and nitrate held at low relative humidity produce only marginal enhancement in absorption. However, liquid-like coatings of glycerol and water produce much larger increases in M.A.C. - presumably due to core-shell lensing. This result suggests the spherical symmetry of soot immersed within liquid particles is important to observe significant absorption enhancement, and measurements made on aerosols at low relative humidity may not adequately reflect absorption by atmospheric soot.