Follow this link to see a overview video on Black Carbon by Dr Tony Hansen the original developer of the Aethalometer
Answers to questions frequently asked regarding Black Carbon may be found in the following links and the references therein:
What is Black Carbon?
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 550nm
- 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
Why measure Black Carbon?
Black carbon in the atmosphere is recognised to play a role in anthropogenic climate change and contribute to pollution related health risks therefore monitoring and source apportionment of ambient black carbon is receiving increasing interest.
The role of Black Carbon in climate change was the subject of a comprehensive assessment conducted by a collaboration of several prominant climate research organisation (Bond et al 2013). Black Carbon influences on climate change included in the assessment were direct absorbtion of sunlight reducing reflectance by the surface of the earth, modification of the processes in ice and liquid clouds changing precipitation, atmospheric temperature structure and cloud distribution and by deposition in snow and ice changing the surface reflectance properties.
WHO published a review of the health effects of Black Carbon in 2001, Short term studies reviewed indicated that Black Carbon, rather than particulate mass (PM10 or PM2.5), is a better indicator of substances posing a health risk from combustion sources (especially traffic). The authors cite a lack of studies to draw strong conclusions on qualitative or quantitave impacts of Black Carbon versus particulate mass or the mechanism of action they postulated based on the evidence reviewed that Black Carbon likely served as a vector for other harmful species to enter the body via the lungs.