What causes acid rain?
(Lansing State Journal, July 12, 1995)
There are a number of sources of sulfur dioxide. A natural source is volcanic eruptions. Many metals in nature are in a combined form with sulfur. When these ores are refined by smelting or roasting, the sulfur in the metal combines with oxygen to form sulfur dioxide. The biggest source of sulfur dioxide is from burning fossil fuels in industry and in homes. Coal contains .5 percent to 5 percent sulfur. Sulfur dioxide released into the air often combines with oxygen to form sulfur trioxide.
Acid rain can be very harmful to stone statues and buildings, forests and aquatic life.