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. 2024 Nov 28;15:10326. doi: 10.1038/s41467-024-54506-5

Fig. 2. Refractive index, carbon chemical bonding, and molecular composition of solid-state strongly absorptive brown carbon.

Fig. 2

Mean (a) real part (n) and (b) imaginary part (k) of RIs against wavelength for solid S-BrC particles from this study and literature7,10,12–18. Shaded areas represent uncertainties. c Averaged STXM/NEXAFS spectra of individual solid S-BrC particles (left y-axis) and the averaged relative abundances of seven functional groups (C=C, C=O, -CH, -NH(C=O), -COOH, -C-OH, and -CO3 (right y-axis)). STXM spectra for solid S-BrC show high -C=C, -COOH, and C-OH contributions. The shaded area in (a–c) represents measurement uncertainties as one standard deviation. d Double bond equivalent (DBE) as a function of the oxygen to nitrogen ratio (O/N) for organonitrate molecular formulae (CHNO compounds) from September 5, 2017, wildfire smoke samples analyzed by 21-T FT-ICR MS. The shaded area represents organonitrates, including nitrophenols, that account for 98% of all detected CHNO molecular formulae.