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Sulfur Dioxide

Sulfur Dioxide


Sulfur dioxide (SO2) is an air pollutant known primarily for its role in acid rain. SO2 is emitted naturally from volcanoes. Anthropogenic emissions arise largely from the production of electricity, particularly coal-fired power plants (65%). The sulfur in the coal reacts with oxygen during combustion, converting it to SO2. Scrubbers, using a slurry of limestone and water, are used to extract the SO2 before it exits the stack.

Once in the atmosphere, SO2 is converted to other compounds such as sulfuric acid (H2SO4), the primary contributor to acid rain. SO2 also reacts to form sulfate aerosols. These tiny airborne particles are the major cause of haze in U.S. national parks.

Both SO2 gas and sulfate aerosols cause breathing problems, particularly for people with existing respiratory illnesses such as asthma. For health reasons, to reduce acid rain, and to improve visibility, SO2 emissions are regulated by a market-based allowance trading system established by the U.S. Environmental Protection Agency (EPA).

see also Acid Rain; Coal; Electric Power; Scrubbers.

Bibliography

Turco, Richard P. (1997). Earth under Siege: From Air Pollution to Global Change. New York: Oxford University Press.


internet resource

Agency for Toxic Substances and Disease Registry (ATSDR). "ToxFAQ for Sulfur Dioxide." Available from http://www.atsdr.cdc.gov/tfacts116.html.

U.S. Environmental Protection Agency Web site. Available from http://epa.gov.

Marin Sands Robinson

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sulfur dioxide

sulfur dioxide, chemical compound, SO2, a colorless gas with a pungent, suffocating odor. It is readily soluble in cold water, sparingly soluble in hot water, and soluble in alcohol, acetic acid, and sulfuric acid. It is corrosive to organic materials and dissolves in water to form sulfurous acid, H2SO3. Sulfur dioxide is used in bleaching and in chemical manufacture and as a refrigerant and a food preservative, e.g., for fumigating fruit. It may be produced by reaction of sulfur with oxygen, e.g., by burning sulfur in air, and it is often produced during the roasting of sulfide ores, e.g., in zinc smelting. Sulfur dioxide is a dangerous air pollutant because of its corrosive properties; it irritates the eyes, nose, and lungs. It is produced by combustion of coal, fuel oil, and gasoline, since these fuels contain sulfur. The sulfur content of a fuel can be reduced by refining, so that less sulfur dioxide is emitted when the fuel is burned.

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sulfur dioxide

sul·fur di·ox·ide • n. Chem. a colorless pungent toxic gas, SO2, formed by burning sulfur in air.

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