Aerosol constituents

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. 

Figure 9. Plots of aerosol constituents in St. Louis, winter 1980 (a) Br vs. Pb (b) elemental C vj. Pb (c) total C vs. Pb and (d) elemental C vs. total C for particulate samples collected during the day (D), during the night (N), and from 3 to...

Van Vaeck, L K. Van Cauwenberghe, and J. Janssens, The Gas-Particle Distribution of Organic Aerosol Constituents Measurement of the Volatilization Artifact in Hi-Vol Cascade Impactor Sampling, Atmos. Environ., 18, 417-430 (1984). 

The mechanisms suggested for PN formation by reactions with aerosol constituents imply that the degree of HN03 retention on previously collected particulate matter would be greatly reduced if coarse particles were excluded from the sampler, and that the extent of HN03 retention with inert prefilters should generally decrease with decreased sampling volume. 

Sulfuric acid may be determined in the presence of other acidic aerosol constituents, but no method for the separation and determination of bisulfate, the most common acidic species in atmospheric aerosols, has been successfully developed. 

A further complication is the basic assumption of the statistical methods that source profiles neither change during air transport nor with time. Therefore they cannot be applied strictly to secondary aerosol constituents formed in the atmosphere by gas-to-particle conversion processes. Still, the secondary aerosol constituents tend to be grouped into one source group since they have a common source , i.e. formation in air triggered by solar irradiation. 

PuxBAUM H, Quintana E and Pimminger M (1985) Spatial distributions of atmospheric aerosol constituents in Linz (Austria) Fresenius Z Anal Chem 322 205-212. 

The behavior in these two different regimes is depicted in Figure 10.23. The transition occurs at approximately 3.5 pgm3. At very low ammonia concentrations, sulfuric acid and bisulfate constitute the aerosol composition. As ammonia increases ammonium nitrate becomes a significant aerosol constituent. The aerosol liquid water content responds nonlincarly to these changes, reaching a minimum close to the transition between the two regimes. 

Arimoto R, Duce RA, Savoie DL et al (1996) Relationships among aerosol constituents Irom Asia and the North Pacific during PEM-West A. J Geophys Res 10 2011-2023 Bacardit M, Camarero L (2009) Fluxes of Al, Fe, Ti, Mn, Pb, Cd, Zn, Ni, Cu, and As in monthly bulk deposition over the Pyrenees (SW Europe) the influence of meteorology on the atmospheric component of trace element cycles and its implications for high mountain lakes. J Geophys Res. doi 10.1029/2008jg000732... 

The proper evaluation of the importance of atmospheric transformation of PAH will require a better understanding of the physical and chemical factors, which influence the reactivity of aerosol constituents during gas-particle interactions, e.g. particle size and specific surface, catalysis of the particle matrix. Thus, more elaborated kinetic and product identification studies are needed. These should not be limited to simplified model systems, but also include the direct exposure of combustion related particles in a reaction chamber to ambient levels of gaseous pollutants. 

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