Elemental carbon atmosphere

Chemical composition data for CPM and FPM for a variety of locations are summarized in Table 5. These data illustrate several important points. First, the distributions of the PM q between CPM and FPM vary from about 0.4 to 0.7. Second, the ratio of PM q to TSP varies from 0.58 to 0.79. In general, both this ratio and the ratio of FPM to PM q tend to be higher at mral sites, but Bermuda, because of the large influence of sea salt in the CPM, is an exception. Sulfate (SO ), carbon (as organic carbon, OC, and elemental carbon, EC), and nitrate (NO3 ) compounds generally account for 70—80% of the FPM. In the eastern United States, compounds are the dominant species, although very Httie is emitted directiy into the atmosphere. Thus... 

Organic compounds are a major constituent of the FPM at all sites. The major sources of OC are combustion and atmospheric reactions involving gaseous VOCs. As is the case with VOCs, there are hundreds of different OC compounds in the atmosphere. A minor but ubiquitous aerosol constituent is elemental carbon. EC is the nonorganic, black constituent of soot. Combustion and pyrolysis are the only processes that produce EC, and diesel engines and wood burning are the most significant sources. 

Human interaction with the global cycle is most evident in the movement of the element carbon. The burning of biomass, coal, oil, and natural gas to generate heat and electricity has released carbon to the atmosphere and oceans in the forms of CO2 and carbonate. Because of the relatively slow... 

The subsequent fate of the assimilated carbon depends on which biomass constituent the atom enters. Leaves, twigs, and the like enter litterfall, and decompose and recycle the carbon to the atmosphere within a few years, whereas carbon in stemwood has a turnover time counted in decades. In a steady-state ecosystem the net primary production is balanced by the total heterotrophic respiration plus other outputs. Non-respiratory outputs to be considered are fires and transport of organic material to the oceans. Fires mobilize about 5 Pg C/yr (Baes et ai, 1976 Crutzen and Andreae, 1990), most of which is converted to CO2. Since bacterial het-erotrophs are unable to oxidize elemental carbon, the production rate of pyroligneous graphite, a product of incomplete combustion (like forest fires), is an interesting quantity to assess. The inability of the biota to degrade elemental carbon puts carbon into a reservoir that is effectively isolated from the atmosphere and oceans. Seiler and Crutzen (1980) estimate the production rate of graphite to be 1 Pg C/yr. 

Abstract. AGB stars, in particular those of carbon types, are excellent laboratories to constraint the theory of stellar structure, evolution and nucleosynthesis. Despite the uncertainties still existing in the chemical analysis of these stars, the determination of the abundances of several key species in their atmospheres (lithium, s-elements, carbon and magnesium isotopic ratios etc.) is an useful tool to test these theories and the mixing processes during the AGB phase. This contribution briefly review some recent advances on this subject. 

All of the above particulate investigations were based on mini-radiocarbon measurement techniques, with sample masses typically in the range of 5-10 mg-carbon. This constituted a major advantage, because it was practicable to select special samples (given region, source impact, sediment depth) and to further subject such samples to physical (size) or chemical separation before 14C measurement. This type of "serial selectivity" provides maximum information content about the samples and in fact it is essential when information is sought for the sources or atmospheric distributions of pure chemical species, such as methane or elemental carbon. 

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. 

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 ... 

Delumyea, R.G. Chu, L-C. Macias, E.S., Determination of Elemental Carbon Component of Soot in Ambient Aerosol Samples, Atmospheric Environment. 1980, 14, 647-652. 

Particulate carbon in the atmosphere exists predominantly in three forms elemental carbon (soot) with attached hydrocarbons organic compounds and carbonates. Carbonaceous urban fine particles are composed mainly of elemental and organic carbon. These particles can be emitted into the air directly in the particulate state or condense rapidly after Introduction into the atmosphere from an emission source (primary aerosol). Alternatively, they can be formed in the atmosphere by chemical reactions involving gaseous pollutant precursors (secondary aerosol). The rates of formation of secondary carbonaceous aerosol and the details of the formation mechanisms are not well understood. However, an even more fundamental controversy exists regarding... 

More recently Cass, Boone and Macias constructed a very detailed carbon inventory for Metropolitan Los Angeles in order to estimate the amount of primary elemental and organic carbon in this urban area ( ). Over 50 source types were included in this emission Inventory. A particulate lead emission inventory was also constructed and used as a tracer for primary automotive exhaust. They compared the ratio of organic carbon to elemental carbon and lead from the emission estimates to that measured in the atmosphere during winter mornings. In that study the sampling time and location were chosen in order to measure... 

Chang, S. G., R. Brodzinsky, L. A. Gundel, and T. Novakov, Chemical and Catalytic Properties of Elemental Carbon, in Particulate Carbon Atmospheric Life Cycle (G. T. Wolff and R. L. Klimsch, Eds.), pp. 159-181, Plenum, New York, 1982. 

Venkataraman, C., and S. K. Friedlander, Size Distributions of Polycyclic Aromatic Hydrocarbons and Elemental Carbon. 2. Ambient Measurements and Effects of Atmospheric Processes, Environ. Sci. Technol., 28, 563-572 (1994b). 

As discussed in Chapter 9.C, ambient particulate matter contains inorganic elements and ions, including trace metals, as well as graphitic (elemental) carbon and a wide variety of organic compounds and water. Techniques in common use to measure these species are discussed very briefly here. For further details of the principles behind these techniques, the reader should consult instrumental analysis texts (e.g., Skoog et al., 1998). Specific applications of various methods to particles in the atmosphere are described in the book edited by Spurny (1986) as well as the references at the end of this chapter. 

The separate determination of organic and elemental carbon in atmospheric particles has been addressed in a number of ways by many workers over a period of... 

Spectrum.5—The arc and spark spectra of tellurium have been investigated, the arc being produced in an atmosphere of carbon dioxide between tellurium electrodes or between carbon electrodes one of which carried pieces of tellurium in a small cavity. Fifteen distinctive lines between 3175 and 2081 A 6 and forty of wave-length less than 2080 A 7 have been measured. The most prominent lines are 2142-75, 2259-02, 2383-24, 2385-76, 2769-65 and 3175-13 A. The lines at 2769-65 and 3175-13 have been shown to be distinct from those of antimony (2769-94) and tin (3175-04) by photographing the spectra of mixtures of these elements with tellurium, when in each case the two separate lines were obtained.8... 

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