Typical Particle Concentrations in the Atmosphere

Given the complexity of particle size distributions in the atmosphere (see Chapter 9.A), as well as the large number of chemical components (Chapter 9.C) that are not distributed equally throughout the various sizes, characterizing a typical collection of particles in the atmosphere is not possible. However, some indication of particle levels in the atmosphere is provided by mass measurements of PMm (i.e., total mass less than 10 gm in diameter), for which extensive measurements have been made for regulatory purposes. 

Concentrations of PMI() in urban areas around the world as high as 300 /rg m 3 have been reported (e.g., Reponen et al., 1996 Kasparian et al., 1998 Morawaska et al., 1998 Lam et al., 1999). In extreme situations such as the fires in Indonesia, 24-h average concentrations of PMI() as high as 900 ggm 3 were 

Concentrations in remote areas are, of course, generally much smaller, as indicated by the much higher visual range in these areas (see Chapter 9). 

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. 

Colorimetry. Colorimetric methods, that is, wet chemical methods in which reagents are added to generate a light-absorbing species whose absorbance can 

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