The alarm regarding the increasing acidification of precipitation in Europe and eastern North America was first sounded in the 1960s. Since then, most attention has focused on acid rain’s effects, established and suspected, on lakes and streams, with their populations of aquatic life, and on forests, although the list of concerns is far broader: It includes contamination of groundwater, corrosion of manmade structures, and, recently, deterioration of coastal waters.
The processes that convert the gases into acid and wash them from the atmosphere began operating long before humans started to burn large quantities of fossil fuels. Sulfur and nitrogen compounds are also released by natural processes such as volcanism and the activity of soil bacteria. However, human economic activity has made the reactions vastly more important. They are triggered by sunlight and depend on the atmosphere’s abundant supply of oxygen and water.
Wood was the first source for energy production. Wood was used for the preparation of food and for heating. After the discovery of fossil fuels in the form of coal as a source of energy, it was used for heating purposes. During the industrial revolution, coal, followed by crude oil and later natural gas, provided a large source of energy that stimulated technological development, resulting in the replacement of animals and people in the production of goods, increased possibilities for mobility, and the enabling of industries to process raw materials into a large variety of products. When the possibilities of energy production and use became apparent, the use of fossil fuels grew exponentially. Figure 1 provides an overview of the worldwide use of fossil fuels since 1900. It shows that the total global energy consumption is closely linked to the growth of the world’s population. The share of oil and gas as energy
FIGURE 1 The worldwide use of fossil fuels in millions of tons per year. Adapted from Smil (2000).
sources has increased and has become higher than the share of coal.
The first environmental consequences of the use of fossil fuels were the problems of smoke in houses and urban air quality. Human health was affected by the use of coal with high sulfur content, producing sulfur dioxide and carbon monoxide. The history of London clearly shows the ever-increasing problems related to coal use and the struggle to abate this pollution, culminating in the famous London smog in 1952, from which thousands of people died. In the 1950s and 1960s, air pollution became an important issue but was mainly considered on the local scale. One of the abatement options was to increase the stack height in order to take advantage of atmospheric dispersion, leading to dilution of pollutant concentrations before humans could be exposed. This formed the basis of the transboundary nature of acid deposition as we know it today and increased the scale from local to regional and even continental. The use of fossil fuels increased, and the pollutants were transported to remote areas, which had very clean air until that time.
Acid rain was first recognized as a serious environmental problem by Robert Angus Smith, an alkali inspector based in Manchester. He started a monitoring network with approximately 12 sites at which rainfall was collected and analyzed. In 1852, he wrote about the correlation between coal burning and acid pollution in and around the industrial center of Manchester. He identified three types of air: ‘‘that with carbonate of ammonia in the fields at a distance... that with sulphate of ammonia in the suburbs, ... and that with sulphuric acid, or acid sulphate, in the town.’’ In 1872, he wrote the famous book, Air and Rain: The Beginnings of a Chemical Climatology. He referred to the acidity of rain and air and its effect on humans and buildings. This was the beginning of acidification research, although this was recognized only much later.
Acid deposition is one of the oldest transboundary environmental problems. Several components and thus emission sources contribute to acid deposition, making it a complex problem and difficult to abate. It is one of the most studied environmental problems and there is a large body of literature. This article gives an overview of the state of knowledge of energy production and use and acid deposition. First, an overview is given of acid deposition, the consequences of acid deposition, and the processes involved. The contribution of energy is discussed next, and an estimate of the progress made to decrease the emissions from energy sources is given. Finally, future options to decrease acid deposition and the options for decreasing energy emissions are discussed.