Articles | Volume 13, issue 15
Atmos. Chem. Phys., 13, 7683–7693, 2013
Atmos. Chem. Phys., 13, 7683–7693, 2013

Research article 09 Aug 2013

Research article | 09 Aug 2013

Absorptivity of brown carbon in fresh and photo-chemically aged biomass-burning emissions

R. Saleh1, C. J. Hennigan2, G. R. McMeeking3, W. K. Chuang1, E. S. Robinson1, H. Coe4, N. M. Donahue1, and A. L. Robinson1 R. Saleh et al.
  • 1Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh PA, USA
  • 2Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County, Baltimore MD, USA
  • 3Droplet Measurement Technologies, Boulder CO, USA
  • 4Centre for Atmospheric Science, University of Manchester, Manchester, UK

Abstract. Experiments were conducted to investigate light absorption of organic aerosol (OA) in fresh and photo-chemically aged biomass-burning emissions. The experiments considered residential hardwood fuel (oak) and fuels commonly consumed in wild-land and prescribed fires in the United States (pocosin pine and gallberry). Photo-chemical aging was performed in an environmental chamber. We constrained the effective light-absorption properties of the OA using conservative limiting assumptions, and found that both primary organic aerosol (POA) in the fresh emissions and secondary organic aerosol (SOA) produced by photo-chemical aging contain brown carbon, and absorb light to a significant extent. This work presents the first direct evidence that SOA produced in aged biomass-burning emissions is absorptive. For the investigated fuels, SOA is less absorptive than POA in the long visible, but exhibits stronger wavelength-dependence and is more absorptive in the short visible and near-UV. Light absorption by SOA in biomass-burning emissions might be an important contributor to the global radiative forcing budget.

Final-revised paper