When the topic of acid rain appears in newspaper headlines or on broadcast news, people who do not understand what it is can react with fear. The term sounds like a phenomenon in a sci-fi thriller that could eat through your clothing or burn your skin. While that isn’t true, the pollution that causes the rain and the chemicals it carries are a danger to the earth.
What is Acid Rain?
Wikipedia defines it as “rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions and low pH.” Particles are also deposited on surfaces without moisture in a process called “dry deposition.” Then, when rain washes the pollutants into a stream, a marsh or other water environment, they become harmful to plants and wildlife. Acid rain is called “wet deposition.”
What Causes the Rain?
When sulphur dioxide, SO2, and nitrogen oxides, NOx, are released into the atmosphere they can be carried for great distances by air currents and wind. They react with water, oxygen and other chemicals to form nitric and sulphuric acids. These compounds mix with water and other contaminants before falling as rain.
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Natural sources like erupting volcanoes generate some of this, but most of the rain is caused by burning fossil fuels. Generation of electricity accounts for roughly two-thirds of the sulphur dioxide in the rain and a fourth of the nitrogen oxides. Vehicles and heavy equipment emit much of the pollution along with manufacturing, in particular oil refining. Normal rain has a pH of about 5.6 percent. The polluted rain has a pH level of 4.2 to 4.4 percent; the power the percentage, the more acidic it is.
How Does the Rain Affect the Earth?
It isn’t dangerous to walk in, but acid rain does affect the health of humans. According to the EPA website, the more acid rain an area receives, the more aluminum is released into the environment. That increased level has been linked to heart and lung problems like asthma and bronchitis.
The ecosystem suffers because of the rain as well. The damage is seen in a domino effect: if one species is stressed or destroyed, it is reflected in the entire system of plants and animals. For instance, a frog may tolerate relatively high levels of pollutants in its system, but the flies upon which it feeds may not have any tolerance. Without the flies, the frogs die. Dead fish in streams are often the first sign of pollution by acid rain. The pollutants damage the young of plant and animal species first.
What is Being Done to Combat the Rain?
The government and environmental agencies in Canada, the continental United States, Alaska, Hawaii and the U.S. Virgin Islands rely upon the 250 collection sites of the National Trends Network of the National Atmospheric Deposition Program to inform them about wet deposition levels. The EPA has pushed through legislation that monitors and caps pollution levels, regulates automobile emissions and limits manufacturing emissions of SO2 and NOx through compliance monitoring and incentive programs. Since acid rin is carried aloft across vast distances, though, it is an environmental danger the whole globe must face.
