Brown carbon absorption linked to organic mass tracers in biomass burning particles

Lack, D. A.; Bahreini, R.; Langridge, J. M.; Gilman, J. B.; Middlebrook, A. M.

Traditional gas and particle phase chemical markers used to identify the presence of biomass burning (BB) emissions were measured for a large forest fire near Boulder, Colorado. Correlation of the organic matter mass spectroscopic m/ z 60 with measured particle light absorption properties found no link at 532 nm, and a strong correlation at 404 nm. Non-black carbon absorption at 404 nm was well correlated to the ratio of the mass fractions of particulate organic matter (POM) that was m/ z 60 ( f60) to m/ z 44 ( f44). The f60 to f44 ratio did not fully explain the variability in non-BC absorption, due to contributions of brown carbon (BrC) absorption and absorption due to internal mixing of POM with black carbon (BC). The absorption Ångstrom exponent ( ÅAbs) showed a good correlation to f60/ f44; however the best correlation resulted from the mass absorption efficiency (MAE) of BrC at 404 nm (MAE POM-404 nm) and f60/ f44. This result indicates that the absorption of POM at low visible and UV wavelengths is linked to emissions of organic matter that contribute to the m/ z 60 mass fragment, although they do not contribute to 532 nm absorption. m/ z 60 is often attributed to levoglucosan and related compounds. The linear relationship between MAE POM-404 nm and f60/ f44 suggests that the strength of BrC absorption for this fire can be predicted by emissions of f60-related organic matter.



Lack, D. A. / Bahreini, R. / Langridge, J. M. / et al: Brown carbon absorption linked to organic mass tracers in biomass burning particles. 2013. Copernicus Publications.


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