Pollutants Sulfur Dioxide (SO2)

Description:
SO₂ belongs to a family of gases called sulfur oxides (SO_x). SO₂ is a colorless, non-flammable gas that is odorless at low concentrations, but at high concentrations can have a pungent and irritating smell. SO₂ can react with NOx and other chemicals in the air to form acid rain.

Source:
Roughly one-third of atmospheric sulfur compounds come from human-made sources. Of this one-third, 70% of annual SO₂ emissions come from electric power plants that burn coal. Burning fossil fuels such as oil, converting wood pulp to paper, and smelting copper, zinc, and lead are also contributors to SO₂ formation. Natural sources of SO₂ include volcanoes and hot springs.

Generally, the highest concentration of SO₂ is found near large industrial sources and power plants. The United States is the largest emitter of SO₂ in the world, emitting some 26 million tons a year.18 When SO₂ enters the atmosphere it is oxidized into SO₃ which then combines with water vapor in the atmosphere to form acid rain. Both wet and dry deposition have been sited as damaging to vegetation and the degradation of soils, building materials, and water bodies.