Radiative absorption enhancement from coatings on black carbon aerosols

The radiative absorption enhancement of ambient black carbon (BC), by light-refractive coatings of atmospheric aerosols, constitutes a large uncertainty in estimates of climate forcing. The direct measurements of radiative absorption enhancement require the experimentally-removing the coating materials in ambient BC-containing aerosols, which remains a challenge. Here, the absorption enhancement of the BC core by non-absorbing aerosol coatings was quantified using a two-step removal of both inorganic and organic matter coatings of ambient aerosols. The mass absorption cross-section (MAC) of decoated/pure atmospheric BC aerosols of 4.4 +/- 0.8 m(2)g(-1) was enhanced to 9.6 +/- 1.8 m(2)g(-1) at 678-nm wavelength for ambiently-coated BC aerosols at a rural Northern China site. The enhancement of MAC (E-MAC) rises from 1.4 +/- 0.3 in fresh combustion emissions to similar to 3 for aged ambient China aerosols. The three-week high-intensity campaign observed an average E-MAC of 2.25 +/- 0.55, and sulfates were primary drivers of the enhanced BC absorption. (C) 2016 Elsevier B.V. All rights reserved.