Secondary inorganic aerosol

FORMATION OF SECONDARY INORGANIC AEROSOLS IN PHOTOCHEMICAL SYSTEMS... 

Sulphates (SO42 ), ammonium (NH4+) and nitrates (NO3 ) are the main secondary inorganic aerosol ions as they account for about two thirds of the total ionic mass in PMj and for about 50% in PM10 in Athens [21], These ions represent two different major source categories fuel combustion and vehicular circulation. Theodosi et al. [21] studied the spatial variability of these ions in 2 sites within GAA Lykovrisi (LYK) and Goudi (GOU). LYK is a moderately populated municipality, in the northern part of the GAA, 10 km from the city centre GOU is located... 

The chemical composition of PM10 shows a considerable conformity in these countries. Always, secondary inorganic aerosols (SIA) are the major constituent ( 40%) followed by the carbonaceous compounds ( 25%). Contributions of sea salt and mineral dust vary between 10% and 15% depending on presence and distance of respective sources. The unidentified mass is some 15% indicating that the composition of PM10 in this region is fairly well known. 

Weijers EP, Sahan E, Ten Brink HM, Schaap M, Matthijsen J, Otjes RP, Van Arkel F (2010) Contribution of secondary inorganic aerosols to PM10 and PM2.5 in the Netherlands measurements and modelling results. PBL Report 500099006, Bilthoven, the Netherlands... 

Fig. 6a Abundance plots constructed for the 4 classes of particles identified by EPXMA analysis for summer (left) and winter (right) airborne particulate matter collected at the Alhambra museum. Aerodynamic diameter (dj size fractions between 0.25 and 16 pm correspond to the stages of the May impactor. For each size fraction in the abundance plot, the total number of analysed particles (N) is indicated on top of the corresponding column. SIA indicates secondary inorganic aerosol particles.

The specific chemicals in particulate matter, an air pollutant, depend on the source and the geographic location. They include inorganic compounds such as sulfate, nitrate, and ammonia organic compounds formed by the incomplete burning of wood, gasoline, and diesel fuels and secondary organic aerosols, new compounds formed when pollutants combine. 

Gas-to-particle conversion is an important secondary source of aerosol surfactants. Inorganic aerosols may acquire an organic component via in situ interactions with volatile organic compounds (VOCs), a family of processes... 

The secondary component results from atmospheric chemical reactions that produce inorganic ionic species of which the most important are NH. and NOJ. Organic vapors also react in the atmosphere to form condensable products. For example, cyclic olefins react with ozone to form less volatile dicarboxyiic acids. The secondary chemical species nomially reported in studies ofaliiiospheric aerosol composition are relatively stable reaction products they have usually survived in the atmosphere and on filter or impactor... 

Water is a major component of the accumulation mode aerosol in amounts that depend on the relative humidity. The uptake of water is driven by the strongly hygroscopic nature of the secondary aerosol components, especially the ainmoniuin sulfates and nitrate. The water content depends in a complex way on both the inorganic and organic components. The resulting aerosol phase solutions are likely to be highly concentrated compared with fog droplets, for example. 

Peterson RE, Tyler BJ (2002) Analysis of organic and inorganic species on the surface of atmospheric aerosol using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Atmos Environ 36 6041-6049... 

Inorganic and organic aerosols that are directly emitted into the atmosphere are known as primary aerosols, for example, aerosols from ocean spray, volcanic eruptions or combustion. Those aerosols that are formed in the atmosphere through a sequence of chemical reactions are referred to as secondary aerosols, and they account for a major component of tropospheric particulates. 

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