Carbonaceous aerosols

Receptor models are powerful tools for source apportionment of particulates because a vast amount of particulate species characterization data have been collected at many sampling sites worldwide, and because many aerosol species are primary pollutants. Most of the information available is for elemental concentrations, eg, lead, nickel, and alurninum, although more recent measurements have provided data on concentrations of ionic species and carbonaceous compounds. At a sampling (or receptor) site, the aerosol mass concentration of each species i is... 

Atmospheric particulates (sea salt, carbonaceous soot, and sulfuric acid aerosols) are known to provide a condensed phase for conq>lex heterogeneous chemistry to occur. Although the presence of atmospheric particulates are known to alter trace gas concentrations, details of the specific chemical mechanisms for condensed phase chemistry have not been identified. 

An important example of the first type is the oil smoke pot which is powered by a slow burning, gassy pyrotechnic mixt such as amm nitrate and amm chloride with a small amount of carbonaceous fuel. The resulting gas jet pulls a stream of oil from a reservoir and injects it into a venturi where the formation of the aerosol takes place... 

Isotopic and chemical patterns are given for an ambient sample (downtown Portland) and four sources of carbonaceous particles. The source C contributions (Ct) are expressed as percent of total aerosol mass, and the subscripts refer to Vegetation (slash burning), Road dust, Oil (residual and distillate), and Auto exhaust. Units for the ordinate are also percent of total aerosol mass, except for, 4C which is expressed as dpm/g-aerosol. Abscissa points for each pattern are ordered as l4C, C, Si, Ni, and Pb. 

For example, studies of the morphology of a number of flame-generated aggregates (different carbonaceous soots, A1203 aerosols, etc.) [203] by both TEM and ALS procedures resulted in D2 = 1.7 0.15, while analysis of silhouettes of computer models of seven proteins [211] gave a value of D2 = 1.120 0.025, etc. 

Some work [5] has been performed on the photochemical reaction between sulfur dioxide and hydrocarbons, both paraffins and olefins. In all cases, mists were found, and these mists settled out in the reaction vessels as oils with the characteristics of sulfuric acids. Because of the small amounts of materials formed, great problems arise in elucidating particular steps. When NO and 02 are added to this system, the situation is most complex. Bulfalini [3] sums up the status in this way The aerosol formed from mixtures of the lower hydrocarbons with NO and S02 is predominantly sulfuric acid, whereas the higher olefin hydrocarbons appear to produce carbonaceous aerosols also, possibly organic acids, sulfonic or sulfuric acids, nitrate-esters, etc. ... 

Nenes, A. Asa-Awuku, A. Padro, E. T. Characterizing the Interactions of Water Vapor with Carbonaceous Aerosol. Proceedings of the 233rd American Chemical Society National Meeting, Chicago, IE, March 25-29, 2007. 

Smoke An aerosol of carbon or soot particles less than 0.1pm in diameter that results from the incomplete combustion of carbonaceous materials such as coal or oil. Smoke generally contains droplets as well as dry particles. 

When sources are studied, several things should be done to provide data needed for receptor-model applications. First, particles should be collected In at least two different size fractions corresponding to the division at about 2.5-ym dlam now used In many studies of ambient aerosols. In some cases. It may be desirable to have more size cuts. As noted above, compositions of particles from coal combustion change dramatically below about 0.5-pm dlam (44, 46). Above we Identified a minimum of about twenty elements that should be measured. Also, In order to develop adequate markers for sources that emit carbonaceous particles, measurements of organic compounds and other properties related to carbonaceous particles should be made. 

Table 3 summarizes the 1979 annual average particle extinction coefficient and the mass concentrations of the fine aerosol chemical species estimated by statistical analysis of the 61 filter samples. Organics and sulfates dominated the chemically determined fine aerosol mass at China Lake in 1979. A linear least squares fit between molar concentrations of NHt and SO gave a zero intercept, a slope of 1.87 and a correlation coefficient of 0.98. It is therefore assumed that the fine sulfate aerosol was in the form of ammonium sulfate. The mass concentration of carbonaceous and sulfate aerosols were, on the average, comparable in magnitude. 

The quality of statistically inferred species extinction balances can be enhanced with proper aerosol sampling. Due to its important role in light scattering, only the fine aerosol should be sampled. A mass balance should account for all major fine particle species. Ideally the particle scattering coefficient should be measured directly at the location where aerosol is sampled by the filters. The importance of soot and other carbonaceous aerosol contributions to light extinction in arid regions should not be overlooked. 

An Automated Thermal-Optical Method for the Analysis of Carbonaceous Aerosol... 

Appel, B.R. Colodny, P. Wesolowski, J.J. "Analysis of carbonaceous materials in Southern California aerosols". Environ. Sci. Technol.. 1976, W, 359-363. 

Johnson, R.L. Huntzlcker, J.J. "Analysis of volatilizable and elemental carbon in ambient aerosols", in "Proceedings Carbonaceous Particles in the Atmosphere", T. Novakov, Ed., Lawrence Berkeley Laboratory, Berkeley, California, June 1979, 10-13. 

Dod, R.L. Rosen, H. Novakov, T. "Optico-thermal analysis of the carbonaceous fraction of aerosol particles", in "Atmospheric Aerosol Research Annual Report 1977-78", Lawrence Berkeley Laboratory, Berkeley, California LBL-8696, pp.2 10. 

Huntzicker, J.J. Johnson, R.L. Shah, J.J. "Carbonaceous aerosol in the vicinity of a Lurgi gasifier", presented at the Second Chemical Congress of the North American Continent, Las Vegas, Nevada, August 1980. 

Aerosol carbon concentrations have been measured at two sites in the Los Angeles basin. Samples were analyzed for total carbon content and for elemental carbon content by the Gamma Ray Analysis of Light Elements technique and by several optical methods. Elemental carbon was shown to constitute a substantial fraction of total carbonaceous aerosol mass in the wintertime in Los Angeles. 

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