Decades ago, acid rain became one of the rallying points for those concerned about the environment. While other issues such as global warming have taken center stage in recent years, the problem still persists although some gains have been made.
The phrase “acid rain” was coined in the 19th century by Robert Angus Smith, but the problem became a widespread issue in the United States in the 1960s when scientists began studying the effects of pollutants ejected into the atmosphere on the environment. The issue was pushed into the limelight in the 1970s by the New York Times, which reported on the effects of acid rain in the Hubbard Brook Experimental Forest in New Hampshire.
By 1980, Congress had passed the Acid Deposition Act, and subsequent legislation (including amendments to the Clean Air Act) sought to control emissions of corrosive sulfur dioxide and nitrogen oxides into the air. Recent studies show some of the areas most impacted by acid rain – New York, Vermont, New Hampshire and Maine – are still enduring the effects, but there are early signs of recovery, according to sciencemag.org.
What Is Acid Rain?
Generally speaking, acid rain is any type of precipitation – rain, snow, fog – that contains a high level of nitric or sulfuric acids. Some of this can be caused by natural phenomenon such as volcanic eruptions and even gases emitted by large amounts of rotting vegetation. However, most acid rain comes from human activities, according to National Geographic.
The primary cause is the burning of fossil fuels. This process releases sulfur dioxide and nitrogen oxides into the atmosphere. When these chemical interact with water and oxygen, the reaction forms a solution of sulfuric and nitric acids that falls back to Earth.
These chemicals then move over the planet’s surface along with rain water, sometimes flowing into water systems and also seeping into the soil.
And while the term acid rain is best known, about half of these chemicals come back to Earth as “dry deposition” via dust or smoke, according to the Environmental Protection Agency (EPA). In this form, the chemicals stick to places such as buildings, cars and homes, and eventually get washed off by falling rain, which turns it more acidic.