What Is Acid Rain

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‘What is acid rain?’ is a question that many people have on their minds as pollution grows worse in many major cities. Most people imagine rain that is so caustic that it literally burns through metal as it falls, but the truth is a little more slow working.

Acid rain is actually a broad term that refers to a mixture of wet and dry deposited material(deposition) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. The chemical forerunners of acid rain formation result from volcanoes and decaying vegetation(natural sources) and emissions of sulfur dioxide and nitrogen oxides resulting from fossil fuel combustion(man-made sources). In the most industrialized nations these emissions mainly come from electric power generation that relies on burning coal. Acid rain occurs when these gases react with water, oxygen, and other chemicals in the atmosphere to form various acidic compounds, which result is a mild solution of sulfuric acid and nitric acid.

Wet deposition refers to acidic rain, fog, and snow. When the acid chemicals in the air are blown into areas where the weather is wet, the acids can fall to the ground in the form of rain, snow, fog, or mist. As this acidic water falls, then flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depends on several factors: how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of flora and fauna involved.

On the other hand, in areas that are arid, the acid chemicals may become part of the dust or smoke and fall to the ground. These chemicals will stick to the ground, buildings, homes, cars, and trees. Dry deposited gases and particles can be washed from these surfaces by rainstorms, leading to increased runoff. This runoff water makes the resulting mixture more acidic. This accounts for about half of the acidity that falls back to Earth.

Knowing what is acid rain is the first step towards doing your part to eliminate it. Doing a little more search will help you to know the steps that need to be taken to lower your carbon footprint.

We have written many articles about acid rain for Universe Today. Here’s an article about air pollution, and here’s an article about the causes of air pollution.

If you’d like more info on air pollution, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:
http://www.epa.gov/acidrain/what/
http://environment.nationalgeographic.com/environment/global-warming/acid-rain-overview/
http://en.wikipedia.org/wiki/Acid_rain

Tagged as: acid rain, air pollution, atmosphere