Light carbon particles

Fig. 10-8. Single particle scattering to mass ratio for particles of four different compositions. Carbon particles are also very efficient absorbers of light. Source U.S. Environmental Protection Agency, "Protecting Visibility," EPA-450/5-79-008, Office of Air Quality Planning Standards, Research Triangle Park, NC, 1979.

Light-absorbing Carbon carbon particles in the atmosphere that absorb light. Black carbon. 

When a composite propellant composed of ammonium perchlorate (AP) and a hydrocarbon polymer burns in a rocket motor, HCl, CO2, H2O, and N2 are the major combustion products and small amounts of radicals such as OH, H, and CH are also formed. These products are smokeless in nature and the formation of carbon particles is not seen. The exhaust plume emits weak visible light, but no afterburning occurs because AP composite propellants are stoichiometrically balanced mixtures and, in general, no diffusional flames are generated. 

The caramelized liquid is sent by railroad tank cars to the cola syrup formulators, who then test the solution for quality. If it is too light in color—penalty if it has too many carbon particles per unit volume, then the whole tank car is rejected. There is thus a delicate balance between underreacting and overreacting. 

Graphitic carbon particles are thought to be the most abundant light-absorbing aerosol species in the atmosphere (2,). Comparison of elemental carbon concentrations from the present study to measurements of b. is presented in Figure 5. A regression line drawn through those data has the equation ... 

An upper limit to the absorption efficiency of the elemental carbon particles sampled can be obtained if it is assumed that all aerosol light absorption is due to elemental carbon. In that case the specific absorption from the slope of the line in Figure 5 is about 11.9 0.9 m g. That value is higher than would be... 

Light Dispersion. The idea of different tints being seen as a scattering spectrum as a result of different carbon particle sizes is intellectually attractive. A word on the general principles involved is in order. 

Carbon particles in the size range we are considering can both absorb and scatter light. Light absorption and conversion to heat (consumptive absorption) are considered below. A further possibility is absorption and re-emission (fluorescence or phosphorescence) which are not explicitly considered here and seem unlikely. Scattering can also result in dispersion of the scattered light, and this is the possibility under consideration. 

The light output of electric lighting gradually decreases due to stain buildup on lamps and covers during operation. Roadway, and especially tunnel lighting, experiences a large amount of contamination due to dust, carbon particles found in vehicle engine exhausts and other airborne contaminants,... 

Figure 22 (Bockhorn, 1994) clearly summarizes the evolution from light molecules to heavy aromatic structures and finally to carbon particles and aggregates. The transition of the species in the gas phase to aerosols and solid particles is possibly the least understood process.

---