“…BrC refers to organic matter in atmospheric particles that absorb light with a strong wavelength dependence (Andreae and Gelencsér, 2006;Alexander et al, 2008;Moise et al, 2015). It exists in various forms, such as soil-derived humic materials, humic-like substances (HULIS), organic materials from combustion processes, bioaerosols (Andreae and Gelencsér, 2006;Salma et al, 2010) and secondary formation in the atmosphere (Laskin et al, 2015;Zarzana et al, 2012;Nguyen et al, 2013;Powelson et al, 2014). Although the chemical composition of BrC is highly complex, light absorption by BrC in the ultraviolet-visible region, quantified by the mass absorption coefficient (MAC) (typically in the range of 0.001-0.1 m 2 g −1 at 500 nm of wavelength , is ascribed to the π -π * and n-π * bond transitions of electrons in the chemicals present.…”