Carbonaceous particles sources

Engines. Vehicular petrol engines are potential ignition sources by means of the spark-ignition system, dynamo or battery, or hot exhaust pipe. Non-flameproof diesel engines are potential ignition sources due to a hot exhaust pipe or carbonaceous particles or flames from the exhaust. 

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. 

Characterization of Their Sources by Low-Level Radiocarbon Counting and Pyrolysis/Gas Chromatography/Mass Spectrometry, Conference on Carbonaceous Particles in the Atmosphere, T. Novakov, ed., University of California, Berkeley, p. 36, 1978. 

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. 

In Fig. 4 an overview of the chemical composition , already grouped according to source processes, of PM10 in Germany is shown. The unaccounted PM mass in these mass closures is frequently around 10-20% which can reasonably be assigned to particle bound water and analytical uncertainties. Higher unaccounted mass fractions in most cases also comprise the mineral dust fraction since analyses of silicon and aluminium are scarcely done in routine. In some studies only the main ionic PM constituents were analysed, and the unaccounted mass then became the major fraction and comprises carbonaceous particles as well. 

The main source of elemental carbon is the (incomplete) combustion of fossil fuels. Wild land fires are occasional sources of vast amounts of carbonaceous particles. Though wild land fires may seem natural, the vast majority of present-day fires are due to human behaviour. Hence, elemental carbon is almost exclusively anthropogenic. 

Primary carbonaceous particles are produced by combustion (pyrogenic), chemical (commercial products), geologic (fossil fuels), and natural (biogenic) sources. Rogge et al. 

Fe-containing particles. Actually, it was found that many Fe-containing particles contain carbon, however, these particles were classihed as Fe-containing. Here, the particles classihed as carbonaceous are mostly composed of carbon, nitrogen, and oxygen without iron. These carbonaceous particles might be from outdoor sources, since it is well known that anthropogenic carbonaceous particles are one of the major chemical species in urban atmosphere. 

A critical requirement for the success of receptor models for atmospheric particles Is that the compositions of particles from all major sources in an area be accurately known. Chemical element balances (CEBs) of 130 samples taken In Washington, D.C. and analyzed for 40 elements yielded nearly the same source strengths when 28 elements are used In the least-squares fit as when only nine carefully chosen elements are used. Certain elements are important to the stability of CEB fits (Na, Ca, V, Mn, As and Pb) and should be measured carefully In particles from sources. For three of the nine elements (Al, Fe and Zn), other elements can serve as surrogates (many lithophlles for Al and Fe, Sb and Cd for Zn). Measurements on many more sources of each Important type should be done In order that trends can be observed that will allow one to predict compositions of particles from unmeasured sources. Instack measurements should Include collections of at least two size fractions of particles plus vapor-phase species. Measurements of at least 20 elements plus some classes of carbonaceous material should be made. 

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... 

Road traffic emissions consist of particulate (PM) and gaseous emissions, with active carbonaceous products present in both phases. Particles contain potentially toxic components, such as polycyclic aromatic compounds (PAHs) and trace metallic elements [4-6], which are related to acute and chronic cardiovascular and respiratory diseases [7]. Some studies suggest that especially diesel exhaust emissions are responsible for cardiac hospital admissions [8] and for asthma and chronic bronchitis development in children [9] in densely populated cities. Also fine and coarse particles from non-exhaust sources have been associated with short-term mortality and morbidity [10-13]. 

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