Behind the Forecast: Why acid rain is not just a problem near volcanoes

Science Behind the Forecast: Acid Rain

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL? at 7:45 a.m.

LOUISVILLE, KY (WAVE) - Acid rain or acid deposition is an imminent threat for those in Hawaii dealing with emissions from the Kilauea volcano, but it is also something that should concern all of us.

Air pollution, such as from our cars, factories and volcanoes, mixes with precipitation creating acid deposition. Acid rain occurs when sulfur dioxide and nitrogen oxides in the atmosphere interact with water, oxygen and other chemicals to create nitric and sulfuric acids. Winds can blow sulfur dioxide and nitrogen oxides a long distance away from their initial sources making it a problem for those significantly downwind.

This precipitation does not have to be just rain; snow, fog, hail and even dust can become acidic.

Dry deposition, such as with acidic dust, occurs when acidic particles and gases accumulate without moisture in the atmosphere. These collect on buildings, plants and even bodies of water reacting with other particles and becoming larger and more harmful to our health.

Acid deposition can cause vegetation kills, fish kills, erosion and health issues. Areas with the greatest acid precipitation issues are usually near or downstream from high air pollution centers.

Acidity and alkalinity are measured on a pH scale where 7.0 is neutral. If a substance has a pH less than 7 then it is acidic; if the pH is higher than 7 it is a base. Rain typically has a pH of 5.6. According to the EPA, acid rain has a pH between 4.2 and 4.4.

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