Global scale pollution

Problems of air pollution exist on all scales from extremely local to global. These are divided in this chapter into five different scales local, urban, regional, continental, and global. The local scale includes up to about 5 km. The urban scale extends to the order of 50 km. The regional scale is from 50 to 500 km. Continental scales are from 500 to several thousand km. Of course, the global scale extends worldwide. 

The harmful effects of air pollutants on human beings have been the major reason for efforts to understand and control their sources. During the past two decades, research on acidic deposition on water-based ecosystems has helped to reemphasize the importance of air pollutants in other receptors, such as soil-based ecosystems (1). When discussing the impact of air pollutants on ecosystems, the matter of scale becomes important. We will discuss three examples of elements which interact with air, water, and soil media on different geographic scales. These are the carbon cycle on a global scale, the sulfur cycle on a regional scale, and the fluoride cycle on a local scale. 

The SO2 in the atmosphere is derived from two sources. Firstly, from the aerial oxidation of H2S produced naturally (see later) and secondly from the combustion of sulphur-containing fuels. In industrialised countries the second source predominates, but on a global scale only about one-fifth of the total sulphur pollution is derived from human activity. In 1969, the total sulphur emission, expressed in terms of SO2, from burnt fuel in the UK was 6-06 X 10 tons. In densely populated countries sulphur pollution levels arc very much related to the domestic heating cycle, and in the UK maximum... 

One of the most significant Indices of air pollution potential Is provided by statistics on motor vehicle use. On a global scale the number of vehicles continues to rise although the rate of growth has slowed In North America and Europe as a whole, where vehicle densities are the highest In the world. Since 1979, the most rapid growth has occurred In Asia and South America where vehicle ownership has more than doubled (11). In the developing countries, as well as many others, these vehicles are not equipped with emission control devices. 

If hydrogen is produced via solar photovoltaic (PV)-powered water electrolysis, it would be possible, in principle, to provide energy on a global scale, with essentially no greenhouse gas emission and veiy low local pollution. 

As discussed in Chapter 1, much of our understanding of the chemistry of our atmosphere is based on early studies of air pollution these are often treated in the context of an overall system. This approach starts with the various sources of anthropogenic and natural emissions and tracks the resulting pollutants through their atmospheric transport, transformations, and ambient concentrations—on local, regional, and global scales—to their ultimate chemical and physical fates, including their impacts on our health and environment. 

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