Most people have heard the words "acid rain" before, but few can give an explanation of this destructive phenomenon. Read on to discover the causes, chemistry, and effects of acid rain!
At its most basic, acid rain is a form of precipitation that is abnormally acidic, as its name suggests. While normal rain has a pH of 5 or 6, acid rain is usually around 4 and has even been recorded with an incredibly low pH of 2. Because of its low pH, it possesses more hydrogen atoms than normal rain does. Acid rain was discovered in 1872 in Sweden, and U.S. scientists began to study it further in the 1950s, but it wasn't widely discussed among the public until as recently as the 1980s.
Acid rain is caused by industrial emissions of certain gasses, namely sulfur dioxide and nitrogen oxide. One interesting thing about this atmospheric phenomenon is that it is both a manmade and natural phenomenon. It occurs naturally when nitrogen oxides are produced during thunderstorms due to lightning heating up the air, and also when sulfur oxides are produced via decomposing vegetation and volcanic eruptions.
However, more focus tends to be placed on the manmade causes of acid rain since these have been increasing throughout the past few centuries. Nitrogen oxide and sulfur dioxide are emitted when fossil fuels like coal and oil are burned, and once they are in the atmosphere, they begin to react with water, oxygen, carbon dioxide, and sunlight to form acids - sulfuric acid and nitric acid. Once the acids then fall to the ground in the form of rain, snow, or hail, they cause negative changes in the chemical environment.
While it was once hailed a widespread threat, acid rain is not talked about much anymore. However, it is still affecting humans and the environment. Science has shown that acid rain has a horrible effect on forests, especially in areas with soils that are not naturally alkaline. This is because the extra acid leeches important minerals from the soil, robbing the trees of what they need to grow strong and healthy.
Acid rain is also devastating for animals and plants that live in lakes. Even if it doesn't fall directly into the lake, the acids from the rain can arrive from rivers and streams. When enough acid rain makes the lake too acidic, some of the lake's life begins to die. A healthy lake has a pH of 6.5 while a few fish can survive in lakes with a pH of 5, but if it reaches a pH of 4, a lake is officially declared "dead." Lakes that appear crystal clear are often those that are devastated by acid rain; they're so clear because hardly anything can live in them anymore.
And it's not just nature that must worry about acid rain. The acid eats away at manmade buildings over time, including buildings made of metal and stone. While this might seem like it doesn't matter, it's not just modern, fixable buildings that suffer damage; it's also famous and culturally significant monuments, such as New York's Statue of Liberty, that have to be painstakingly restored after the effects of acid rain.
Human health is put at risk as well by this threat from the sky. Acidic water moving through pipes causes lead and copper to leech into the water, polluting water supplies for those who don't rely on public water (which filters these out) for their drinking water. Acidic fog, since it can be inhaled easily, is particularly dangerous for the elderly and people with weak immune systems or chronic respiratory conditions.
The bad news for some and good news for others is that acid rain doesn't necessarily fall around industrial sites where sulfur dioxide and nitrogen oxide are emitted. Because of wind patterns and air currents, pollution can end up a long way from where it was produced, making acid rain a concern even for those who live far away from large centers of fossil fuel burning. This underscores the need for states and countries to work together on reducing the pollution that causes acid rain, for the good of everyone.