Black carbon (BC) or elemental carbon (EC) is considered the second most important climate
warming agent after CO2. BC is one of the components of ambient particulate matter (PM). The high
absorption efficiency of BC is due to its electronic structure and composition that allows BC particles
to absorb electromagnetic radiation over a wide range of wavelengths. The mass absorption crosssection
(MAC) represents the efficiency that a BC particle has for absorbing light at a given
wavelength and it is related to EC via eq. 1. Photochemical ageing of BC due to mixing with nonabsorbing
(or less absorbing) particles, such as sulfate or organic aerosols, can increase the
apparent MAC of BC above that of an uncoated BC particle.Peer reviewe
