Sulfur Dioxide

Sulfur dioxide is another pollutant with both natural and anthropogenic origins. Sulfur dioxide is emitted into the atmosphere when coal, oil, and other sulfur containing fuels are burned. Major sources of sulfur dioxide are petroleum refineries, power plants, paper mills and smelters. Volcanic activity also releases around 10⁹ kg of sulfur per year in the form of SO₂. Sulfur dioxide can oxidize to form sulfur trioxide (SO₃) and can react with moisture in the air to form sulfuric acid (H₂SO₄). Sulfuric acid in the atmosphere can also cause respiratory problems such as bronchitis and emphysema. Sulfuric acid is also deposited in the form of acid rain which can damage plant life, destroy man-made monuments and structures, and devalue personal property.

The graphic at the right shows sources of SO2 for the United States. The majority of SO2 emissions come from electrical utilities, especially in the eastern part of the United States. Pulp and paper mills also contribute a fairly significant amount to the total SO2 emissions per year. Indeed, driving past a paper mill will quickly convince you that sulfur products are being emitted, assuming your sense of smell is functional!

Graphic from US EPA

The graphic at the left (click on graphic to see full-sized) shows SO2 emissions in the United States by county. This data comes from the US EPA National Air Quality Standards report. It is relatively clear that there is an abundance of high emissions counties in the eastern United States, especially throughout the Ohio Valley and up into the northeastern United States.