Analysis of Brown Carbon Content and Evolution in Smokes from Siberian Forest Fires Using AERONET Measurements

Abstract

The content and evolution of brown carbon (BrC) in smokes from Siberian forest fires were analyzed using measurements of the aerosol absorption optical depth (AAOD) at three Russian AERONET stations located in Tomsk, Zvenigorod, and Yekaterinburg. Estimates are obtained of the relative contribution of BrC in fine aerosol particles to the absorption of solar radiation at a wavelength of 440 nm (ηBrC) and, in particular, for an anomalous episode of long-range transport of smokes from Siberia to the European part of Russia in summer 2016. A considerable BrC content is found in smokes in Tomsk and Zvenigorod (where ηBrC is estimated to be 15 and 18% on average). It is noteworthy that no significant ηBrC values were revealed during passage of smokes from Siberian fires over Yekaterinburg. The ηBrC values were found to decrease with aerosol aging under sunlit conditions on the characteristic timescale of about 30 h. At the same time, the measurements in Zvenigorod indicate that the absorption properties of the organic component of smoke aerosol increase during a much longer evolution.