Operationally defined species and aerosols based on the measurement of light absorption and chemical reactivity and/or thermal stability. It is sometimes referred to as soot. BC is mostly produced by incomplete combustion fossil fuels,  biofuels  a biomass , but also occurs naturally. In the atmosphere only a few days or weeks remain. It is the most strongly light-absorbing component of particulate matter (PM) and has a warming effect by absorbing heat into the atmosphere and reducing albedo. when is deposited on snow or ice.

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