Source-Specific Mass Absorption Efficiencies of Char-EC and Soot-EC Improve Accuracy in Black Carbon Radiative Effect Estimation

Abstract

Optical properties of elemental carbon (EC) are critical for climate modeling due to its strong light absorption. Elemental carbon consists of char-EC and soot-EC, which differ in mass absorption efficiency (MAE). However, the MAEs of these forms remain underexplored primarily due to the limited methods available for measurement, limiting the accuracy of EC climate impact assessments and leading distortions of EC radiative effect in the temporal and spatial distribution. In this study, we derived MAEs for char-EC and soot-EC using combined modeling methods based on observational data, revealing key differences. Soot-EC generally has higher MAEs than char-EC, except from biomass burning. Meteorological factors, such as relative humidity, also influence the MAEs of char-EC and soot-EC differently. The differences in sources and aging process lead to changes in the mass concentration and MAE of char-EC and soot-EC over time. Ignoring these differences can lead to discrepancies in the radiative effect from −9.1% to 18.7%. This study underscores the importance of considering the char-EC and soot-EC in accurate EC radiative effect estimates, and implies that optimizing the management of different black carbon emission sources would mitigate global warming to varying extents due to the divergence of the char/soot emission ratio and their MAE.