Production of particulate brown carbon during atmospheric aging of residential wood-burning emissions

We investigate the optical properties of light-absorbing organic carbon (brown carbon) from domestic wood combustion as a function of simulated atmospheric aging. At shorter wavelengths (370\u2013470\u2009nm), light absorption by brown carbon from primary organic aerosol (POA) and secondary organic aerosol (SOA) formed during aging was around 10\u2009% and 20\u2009%, respectively, of the total aerosol absorption (brown carbon plus black carbon). The mass absorption cross section (MAC) determined for black carbon (BC, 13.7\u2009m2\u2009g 121 at 370\u2009nm, with geometric standard deviation GSD\u2009=1.1) was consistent with that recommended by Bond et al. (2006). The corresponding MAC of POA (5.5\u2009m2\u2009g 121; GSD\u2009=1.2) was higher than that of SOA (2.4\u2009m2\u2009g 121; GSD\u2009=1.3) at 370\u2009nm. However, SOA presents a substantial mass fraction, with a measured average SOA\u2009 15\u2009POA mass ratio after aging of 3c5 and therefore contributes significantly to the overall light absorption, highlighting the importance of wood-combustion SOA as a source of atmospheric brown carbon. The wavelength dependence of POA and SOA light absorption between 370 and 660\u2009nm is well described with absorption \uc5ngstr\uf6m exponents of 4.6 and 5.6, respectively. UV-visible absorbance measurements of water and methanol-extracted OA were also performed, showing that the majority of the light-absorbing OA is water insoluble even after aging.Peer reviewed: YesNRC publication: Ye