Biomass burning dominates brown carbon absorption in the rural southeastern United States

Abstract

Brown carbon aerosol consists of light-absorbing organic particulate matter with wavelength-dependent absorption. Aerosol optical extinction, absorption, size distributions, and chemical composition were measured in rural Alabama during summer 2013. The field site was well located to examine sources of brown carbon aerosol, with influence by high biogenic organic aerosol concentrations, pollution from two nearby cities, and biomass burning aerosol. We report the optical closure between measured dry aerosol extinction at 365 nm and calculated extinction from composition and size distribution, showing agreement within experiment uncertainties. We find that aerosol optical extinction is dominated by scattering, with single-scattering albedo values of 0.94 ± 0.02. Black carbon aerosol accounts for 91 ± 9% of the total carbonaceous aerosol absorption at 365 nm, while organic aerosol accounts for 9 ± 9%. The majority of brown carbon aerosol mass is associated with biomass burning, with smaller contributions from biogenically derived secondary organic aerosol.

Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets

“…Site description and instruments involved during the SOAS campaign are detailed elsewhere (8,(16)(17)(18). Ambient air was continuously drawn with mechanical pumps through two inlets.…”

Light absorption of brown carbon aerosol in the PRD region of China

“…at 365 and 405 nm, and contribute approximately 10 % at midvisible wavelengths, e.g. at 532 nm (Bahadur et al, 2012;Lack et al, 2012b;Washenfelder et al, 2015;Nakayama et al, 2014). During an agricultural waste burning event, BrC aerosol could contribute more than 65 % of light absorption at 370 nm and 15 % at a mid-wavelength (Favez et al, 2009).…”

Relative importance of black carbon, brown carbon, and absorption enhancement from clear coatings in biomass burning emissions

“…Potential sources of BrC include emissions from biomass burning (Kirchstetter et al, 2004;Moosmüller et al, 2009;Chen and Bond, 2010;Lack et al, 2012a;Saleh et al, 2014;Washenfelder et al, 2015); incomplete combustion of fossil fuels, especially coal (Bond, 2001;Yang et al, 2009;Olson et al, 2015); and secondary organic aerosols (Saleh et al, 2013;Zhang et al, 2013;Lin et al, 2015). There exists significant uncertainty concerning the relative contribution of each of these source types to total BrC concentrations, but several studies have identified biomass burning as a potentially significant source (Washenfelder et al, 2015;McMeeking et al, 2014;Lack et al, 2012a).…”

“…There exists significant uncertainty concerning the relative contribution of each of these source types to total BrC concentrations, but several studies have identified biomass burning as a potentially significant source (Washenfelder et al, 2015;McMeeking et al, 2014;Lack et al, 2012a). Open biomass burning (BB) is one of the largest global sources of BC and organic carbon (OC), and biomass burning emissions have a significant direct effect on the Earth's radiative balance (Bond et al, 2013).…”

“…Laboratory measurements of absorption enhancement in biomass burning aerosols show significant variation with values greater than 2 observed at 405 nm in some samples and values ranging from 1.2 to 1.5 at 532 and 781 nm (McMeeking et al, 2014). There are a number of studies that estimate the absorption due to BrC in the blue and ultraviolet wavelengths (Yuan et al, 2016;Washenfelder et al, 2015;Guo et al, 2014;Lack et al, 2012a;Cappa et al, 2012;Bahadur et al, 2012;Flowers et al, 2010;Wang et al, 2016;Stockwell et al, 2016). Results from these studies show large variations in the estimated percentage of absorption attributable to BrC.…”