Black carbon absorption enhancement in the atmosphere determined by particle mixing state

Dantong Liu, James Whitehead, Mohammedrami Alfarra, Ernesto Reyes Villegas, Dominick Spracklen, Carly L. Reddington, Shaofei Kong, Paul Williams, Yu-Chieh Ting, Sophie Haslett, J. W. Taylor, Michael Flynn, William Morgan, Gordon Mcfiggans, Hugh Coe, James Allan

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    Atmospheric black carbon makes an important but poorly quantified contribution to the warming of the global atmosphere. Laboratory and modelling studies have shown that the addition of non-black carbon materials to black carbon particles may enhance the particles’ light absorption by 50 to 60% by refracting and reflecting light. Real world experimental evidence for this ‘lensing’ effect is scant and conflicting, showing that absorption enhancements can be less than 5% or as large as 140%. Here we present simultaneous quantifications of the composition and optical properties of individual atmospheric black carbon particles. We show that particles with a mass ratio of non-black carbon to black carbon of less than 1.5, which is typical of fresh traffic sources, are best represented as having no absorption enhancement. In contrast, black carbon particles with a ratio greater than 3, which is typical of biomass burning emissions, are best described assuming optical lensing leading to an absorption enhancement. We introduce a generalised hybrid model approach for estimating scattering and absorption enhancements based on laboratory and atmospheric observations. We conclude that the occurrence of the absorption enhancement of black carbon particles is determined by the particles’ mass ratio of non-black carbon to black carbon.
    Original languageEnglish
    Pages (from-to)184–188
    JournalNature Geoscience
    Early online date27 Feb 2017
    Publication statusPublished - 27 Feb 2017


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