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A lack of information on the radiative effects of refractory black carbon (rBC) emitted from biomass burning is a significant gap in our understanding of climate change. A custom-made combustion chamber was used to simulate the open burning of crop residues and investigate the impacts of rBC size and mixing state on the particles’ optical properties. Average rBC mass median diameters ranged from 141 to 162 nm for the rBC produced from different types of crop residues. The number fraction of thickly-coated rBC varied from 53 to 64%, suggesting that a majority of the freshly emitted rBC were internally mixed. By comparing the result of observed mass absorption cross-section to that calculated with Mie theory, large light absorption enhancement factors (1.7–1.9) were found for coated particles relative to uncoated cores. These effects were strongly positively correlated with the percentage of coated particles but independent of rBC core size. We suggest that rBC from open biomass burning may have strong impact on air pollution and radiative forcing immediately after their production.

© 2018 Elsevier Ltd. All rights reserved.

Appear in Atomspheric Environment

Authors: Qiyuan Wang, Junji Caoa, Yongming Hana, Jie Ti, and Yue Zhang, Siwatt Pongpiachan, Yonggan Zhang, Li Li, Xinyi Niu,Zhenxing Shen, Zhuzi Zhao, Danai Tipmanee, Suratta Bunsomboonsakul, Yang Cheng, Jian Sund

Highlights
• Insignificant correlations were found between rBC MMDs and combustion conditions.
• The fraction of thickly-coated rBC was anti-correlated with combustion conditions.
• Large absorption enhancements were found in fresh biomass-burning emissions.

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