D

c = Polar fraction

Fig. 36

Mass concentration of all aerosol particles (P) and of organic particles at different sampling sites according to Ketseridis et al. (1976). E: ether extractable organic material; N: neutral organic compounds; A : organic acids; B: organic bases. (By courtesy of Atmospheric Environment) Note : The majority of the mass of all particles under marine conditions is sea salt (see Fig. 34). The numbers behind the names of the sampling locations give the number of samples analyzed

14 Woodcock's classical studies demonstrated (Woodcock, 1953) that the number of giant sea salt particles decreases rapidly with increasing height over the ocean.

the direct chemical bulk analyses of Winkler (1975) also clearly indicate that the main component of the aerosol in the Aitken size range is sulfur under oceanic background conditions.

It is believed that this huge amount of smaller sulfur (sulfate) particles come into being by the chemical and physical transformations discussed in Subsections 3.6.3 and 4.2.2. This assumption is strongly indicated by the greater prevalence of ammonium sulfate particles near the equator, where conditions are very favourable for the initiation of photochemical and thermal reactions.

The organic fraction of atmospheric particulate matter was investigated by Ketseridis et al. (1976) at several locations, including remote oceanic areas. These authors collected particles on glass fiber filters and determined the total mass of suspended particles by weighing the filters before and after the sampling. They extracted ether soluble materials from the samples and were able to identify chemically organic acids and phenols, organic bases, aliphatic hydrocarbons, aromatic hydrocarbons and neutral compounds. The results obtained are summarized in Fig. 36. The data labelled 'Meteor' refer to samplings carried out on board the German research vessel Meteor in 1973 over the North Atlantic. It is to be noted that during Part II of this expedition as well as during sampling in Cape Verde an advection of Sahara dust was observed. One can see that, except in more polluted atmospheres, the concentration of organic material extractable in ether is practically constant at about 1 /¿g m ~3 STP. The fraction of different components is also independent of sampling location. At Jungfraujoch and over the Atlantic Ocean (without dust advection) about 5-10 % of the aerosol particle mass is composed of organics. Ketseridis et al. (1976) speculated that this constant concentration of organic particulate matter in tropospheric background is either due to particle advection from highly populated areas or to a constant production

Table 22

Chemical composition of aerosol particles in the upper troposphere over the Philippine Islands on November 19, 1969, from the aircraft measurements of

Cadle (1973)

Table 22

Chemical composition of aerosol particles in the upper troposphere over the Philippine Islands on November 19, 1969, from the aircraft measurements of

Cadle (1973)

Latitude

Longitude

Height

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