Super Eco

Acid rain is the result of sulfur dioxide (SO₂) and nitrogen oxides(NOx) reacting in the atmosphere with water to create an acid, and returning to earth as rain, fog, or snow. Acid rain can also refer to the dry deposition of these acids as particles of dust downwind from the source of the SO₂ and the NOx. The United States Environmental Protection Agency says that acid rain is a serious environmental problem that affects large parts of North America. Acid rain damages lakes, streams, and forests and the plants and animals that live in them.

SO₂ is largely the product of fossil fuel combustion by power-production companies and other heavy industry. The combustion releases sulfur into the air that combines with oxygen to form sulfur dioxide. NOx is produced by automobile exhaust. From these gases, airborne sulfuric acid (H₂SO₄) and nitric acid (HNO₃) often form and dissolve in the water vapor in the air. Acid rain "fallout" affects the environment for hundreds of miles downwind of the pollution source.

In the United States and around the world, there has been a growing awareness that pollution and acid rain are accelerating the deterioration of buildings and monuments. In Philadelphia the marble pillars of the First Bank of the United States (built in the late 1700s) have been seriously eroded by acid. In Athens, Greece, significant deterioration of the Parthenon and surrounding sculptures is attributed to acid rain caused by human activity.

In general, acid rain is a human-related phenomenon. Reducing the use of fossil fuels, including the use of electricity generated by coal- and oil-fired power plants, helps reduce acid rain-causing emissions. The US EPA reports success in reducing emissions through the Acid Rain Program, a cap and trade emissions market authorized by the 1990 Amendments to the Clean Air Act.

 (Photo Credit: Michael Gray, Flickr)