What is Black Carbon?

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USEPA report to congress on Black Carbon (2012) defined Black Carbon as: A solid form of mostly pure carbon that absorbs solar radiation (light) at all wavelengths.  Black carbon (BC) is the most strongly light-absorbing component of particulate matter (PM) and is formed by the incomplete combustion of fossil fuels, biofuels, and biomass.

Black Carbon was further defined, by Bond et al 2013, as ambient aerosol matter with the following characteristics:

  • Strongly absorbs visible light with absorbtion cross section of at least 5m2g-1 at 550mm
  • Refractory (stable at high temperatures) with vaporization temperatures near 4000k
  • insoluble in water and orgainc solvents and other components of atmospheric aerosol
  • Is an aggredate of small carbon spherules

Sources of the majority of black carbon rich emissions can be broadly categorised into diesel engines, industry, residential solid fuel buring (coal and biomass) and open burning.  


The following are further common nomenclature used when discussing Black Carbon as defined by the USEPA (USEPA report to congress on Black Carbon 2012).

Elemental Carbon - A descriptive term for carbonaceous particles that is based on chemical composition rather than light-absorbing characteristics.

Biomass - In the context of energy, the term biomass is often used to refer to organic materials, such as wood and agricultural wastes, which can be burned to produce energy or converted into a gas and used for fuel.

Brown Carbon - A class of particulate organic carbon compounds that absorb ultraviolet and visible solar radiation. Brown Carbon can be directly emitted as a product of incomplete combustion, or it can be formed in the atmosphere as pollutants age.

Organic Carbon - The mix of compounds containing carbon bound with other elements; e.g., hydrogen and oxygen. Organic carbon may be a product of incomplete combustion, or formed through the oxidation of VOCs in the atmosphere. Both primary and secondary organic carbon possess radiative properties that fall along a continuum from light-absorbing to light-scattering.

Carbon Mass Ratio - The ratio of the mass of different components of carbonaceous particles (e.g., the ratio of organic carbon to black carbon, or the ratio of black carbon to total particulate matter).

Bond et al 2013 Journal of Geophysical Reserach:Atmospheres 118 (11) 5380–5552