Strong acids, atmospheric definitions

There are numerous hypotheses-but few definitive results-as to what physicochemical characteristics of atmospheric particles are responsible for adverse health effects (Samet 2000 Schlesinger 2000). Hypotheses include general properties such as mass, surface area, or size, as well as more specific chemical properties such as acidity or elevated concentrations of transition metals (Dreher et al. 1997 Samet 2000). For example, it has been suggested that particulate iron is toxic due to its ability to generate the strongly oxidizing hydroxyl radical through the Fenton reaction (Ohio et al. 1996 Smith and Aust 1997 Donaldson et al. 1998 van Maanen et al. 1999) ... 

Whereas the atmosphere is uniform laterally and varies in stracture only with altitude, the hydrosphere consists of many distinct reservoirs of differing size. These are the seas and oceans, with a limited range of variation in composition and a definite vertical stracture lakes, with a wide range of chemical variation and also vertical stratification rivers, with highly variable composition but little stracture precipitation (rain, snow, fog, mist), whose only important compositional variable is pH (degree of acidity) and groundwater, whose composition depends strongly the character of the soils or minerals with which it is in contact. 

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