The causes of acid deposition are the quantities of sulfur oxides (Figure 7.19) and nitrogen oxides emitted from fossil-fuel combustion. Figure 7.20 shows how sulfate levels increased in European precipitation between the 1950s and 1970s. Two main factors contributed to the increasing seriousness of the problem at the time. One was the replacement of coal by oil and natural gas. The second, paradoxically, was a result of the implementation of air pollution control measures (particularly increasing the height of smokestacks and installing particle precipitators). These appear to have transformed a local ‘soot problem’ into a regional ‘acid rain problem’. Coal burning produced a great deal of 1860 1880 1900 1920 1940 1960 1980 1990
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