Acid Deposition and Energy Use
JAN WILLEM ERISMAN
Energy Research Centre of the Netherlands Petten, The Netherlands
1. Introduction
2. Acid Deposition, Its Effects, and Critical Loads
3. Processes in the Causal Chain: Emission, Transport, and Deposition
4. Emissions from Energy Use
5. Abatement and Trends in Emission
6. Acid Deposition
7. Benefits and Recovery of Ecosystems
8. Future Abatement
9. Conclusion
Glossary
acid deposition The removal of acidic or acidifying components from the atmosphere by precipitation (rain, cloud droplets, fog, snow, or hail); also known as acid rain or acid precipitation.
acidification The generation of more hydrogen ions (H +) than hydroxide ions (OH-) so that the pH becomes less than 7.
critical level The maximum pollutant concentration a part of the environment can be exposed to without significant harmful effects.
critical load The maximum amount of pollutant deposition a part of the environment can tolerate without significant harmful effects.
deposition Can be either wet or dry. In dry deposition, material is removed from the atmosphere by contact with a surface. In wet deposition, material is removed from the atmosphere by precipitation.
emissions The release of primary pollutants directly to the atmosphere by processes such as combustion and also by natural processes.
eutrophication An increase of the amount of nutrients in waters or soils.
nitrification The conversion of ammonium ions (NH4) to nitrate (NO-).
nonlinearity The observed nonlinear relationship between reductions in primary emissions and in pollutant deposition.
pollutant Any substance in the wrong place at the wrong time is a pollutant. Atmospheric pollution may be defined as the presence of substances in the atmosphere, resulting from man-made activities or from natural processes, causing effects to man and the environment.
Acid deposition originates largely from man-made emissions of three gases: sulfur dioxide (SO2), nitrogen oxides (NOx), and ammonia (NH3). It damages acid-sensitive freshwater systems, forests, soils, and natural ecosystems in large areas of Europe, the United States, and Asia. Effects include defoliation and reduced vitality of trees; declining fish stocks and decreasing diversity of other aquatic animals in acid-sensitive lakes, rivers, and streams; and changes in soil chemistry. Cultural heritage is also damaged, such as limestone and marble buildings, monuments, and stained-glass windows. Deposition of nitrogen compounds also causes eutrophication effects in terrestrial and marine ecosystems. The combination of acidification and eutrophication increases the acidification effects. Energy contributes approximately 82, 59, and 0.1% to the global emissions of SO2, NOx, and NH3, respectively. Measures to reduce acid deposition have led to controls of emissions in the United States and Europe. Sulfur emissions were reduced 18% between 1990 and 1998 in the United States and 41% in Europe during the same period. At the same time, emissions in Asia increased 43%. In areas of the world in which emissions have decreased, the effects have decreased; most notably, lake acidity has decreased due to a decrease in sulfur emissions, resulting in lower sulfate and acid concentrations. However, systems with a long response time have not seen improvement yet and very limited recovery has also been observed. Emissions should therefore be further reduced and sustainable levels should be maintained to decrease the effects and to see recovery. This will require drastic changes in our
energy consumption and the switch to sustainable energy sources. Before renewable energy sources can fulfill a large part of our energy needs, the use of zero-emission fossil fuels must be implemented. This should be done in such a way that different environmental impacts are addressed at the same time. The most cost-effective way is to reduce CO2 emissions because this will result in decreases in SO2 and NOx emissions. When starting with SO2 and NOx emissions, an energy penalty compensates for the emission reductions.
