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Acid Rain

What is this?

What is Acid Rain?

Pure rain is a slightly acidic, naturally-occurring substance formed when carbon dioxide mixes with the water vapor in earth’s atmosphere. The new vapor droplets gather together and create clouds. When those droplets become too heavy, gravity pulls them down as rain.

Acid rain is a problematic environmental issue produced from various sources of air pollution. Sulfur dioxide and nitrogen oxide are pollutants emitted from transportation vehicles, use of solvents, and fires, but their primary source comes from industrial processes such as burning fossil fuels and generating electricity. It is the absorption of these pollutants into the air that creates the matter which descends as acid deposition (1), falling as dry particles or wet matter like rain, snow, and sleet. The pollutants mix with rain, acidic levels rise, and acid precipitation is born.

What impact does it have?

What impact does Acid Rain have?

The effects of acid rain are numerous. It upsets natural elements like lakes and streams, aquatic life, and forests, as well as affecting human-made artifacts like buildings and other outdoor structures, statues, and automobiles. Acid rain also puts human health at risk and reduces visibility.

Oceans, lakes, and streams have a normal pH (2) range of 6.0-8.0. However, unlike an ocean whose calcium carbonate offsets acidic compounds, when acid rain falls on the water and soil of lakes and streams, the limited buffering capacity (3) cannot neutralize the acid. Acid rain harms aquatic life by increasing aluminum levels in the water as the pH decreases. Aluminum is toxic to many water animals and plants. Though it is not an instant ailment, over time acid rain will kill the plants and animals, stunt their growth, and prevent the hatching of babies.

Acid rain, in combination with other factors such as air pollutants, insects, and extreme weather, causes the most damage to trees and forests. Soil buffering capacity differs depending on the amount and composition of soil and bedrock under the forest ground; therefore some areas barely show a sign of acid precipitation while others are destroyed by it. As with its effects on water, acid rain is not an instant threat to trees. In areas with a low buffering capacity, trees grow slowly and fragilely because of the decreased nutrients in acidic soil. Acid also eats at leaves, causing them to brown and fall off during seasons when they should be green and luscious.

Rugged materials like metal, paint, and stone, found in the outer surfaces of buildings, statues, bridges, and automobiles, erode when in contact with acid rain and acidic dry deposition. Monuments, tombstones, and other important societal or cultural structures are often damaged, lost by the dangerous pollutant.

Humans are not hurt by direct contact with acid rain; rather it is the sulfur dioxide and nitrogen oxide particles that cause harm to them. As these particles float through the air, they are breathed in to the human body, leading to heart and lung diseases. Also, eyes strain to see clearly through the haze created by acid deposition.


What has been done about it?

What has been done about Acid Rain?

There are a number of solutions to acid rain. Environmental organizations have worked hard to inform the public of the causes and effects of acid rain. People need to know what it is and why it occurs in order to begin resolution. Individuals can go green by turning off lights, televisions, and computers when not using them. They carpool or walk when possible, leave the household thermostat set steadily, and use energy-efficient appliances.

Small groups attempt outdoor clean-up activities. Lime, a natural basic compound, is added to lakes and streams to reverse the damage done to the ecosystem by acid deposition.

Industrial plants also go green by taking small (and large) steps to reduce pollutants from leaving their chimneys. Coal is washed before use to decrease surface pollutants, and some factories commit to using only coal with low sulfur content. Alternative energy sources, like hydropower, wind, and solar energy, are established to run pollution-free. Also, scrubbers4 are set up to remove sulfur compounds from coal combustion.

Is this action working?

Are Acid Rain reduction actions working?

Individual actions do help reduce acid rain-causing pollutants. Every little deed goes toward the big picture. If each person followed these simple green living steps, larger amounts of air pollutants would avoid entering the atmosphere.

Small groups or environmental organizations often go out into an affected area to clean up the pollution. Since acid deposition is invisible in its dry form and unnoticeable when wet, it is impossible to really clean it up. Only after careful examination, continuous studies, and a long wait time can the effects of acid rain be declared. However, it is known that acid deposition changes the chemistry of soil and water, so that it will take up to several years for things to return to normal. In Europe, specifically Sweden and Norway, lime is added to lakes and streams to neutralize acidic compounds, and they have had success in doing so. In the United States, on the other hand, liming is considered a short-term solution and is not usually carried out because it does not address effects of acid deposition on things other than lakes and streams, it does not readjust the soil and water chemistry, and it must be performed continuously to prevent acidity from returning.

Over the past decade, sulfur emissions from industrial plants have been reduced from the efforts taken by these factories. Using coal with low sulfur content logically produces less sulfur emissions, but it does not create the amount of heat that burning standard coal does. As a result, more coal will be collected for combustion purposes. Washing coal prior to use will rid the coal of its pyritic surfactants, but the chemically-imbedded sulfur will still be present. The use of scrubbers (4) has positive and negative effects. Though they do capture most, if not all, of the sulfur compounds, they leave a waste product, in powder or paste form, which must then be disposed of. The by-product can sometimes be recycled as drywall or other such products, but if it cannot, the waste is either stored or buried in a landfill. How much can be stored and how earth-safe the product is remain of great concern. Alternative energy is wonderful because it offers pollution-free, renewable sources, but these methods have not been established on a large enough scale to really be used successfully and cost-efficiently by all large energy producers.

Should it continue? On one side, there are those who are against

Should Acid Rain reduction actions continue?

As with most environmental issues, there is great debate in the worthwhileness of acid rain reduction efforts. All in all, efforts are circling around.

The actions taken by individual citizens to help lower the amount of air pollution emissions which lead to acid rain are very small-scale compared to the solutions large, industrialized plants have to offer. Nonetheless, green living is important in showing that even baby steps can take you where you want to be, and most people agree.

Liming river, lakes, and streams in attempts to decrease acidity, at least for the United States, has not proven beneficial. Though it does help, it becomes a very time-consuming process, and since it must be constantly repeated, it also becomes quite costly. Government organizations feel that money can be better budgeted towards other efforts.

Unfortunately, the process of planning, licensing, and producing devices and control systems to slow the release of acid rain-causing pollutants can take years and unimaginable amounts of money. Some people feel that any reduction in emissions is worth whatever it takes, while others feel this strong effort is then only good for the 30 or so years a factory remains open.

Industrial plants have tested various solutions, but so far, nothing is full proof. In an ironic twist, past studies showed that, as the sulfur emissions were cut, there was a decrease in alkaline particles, which help to balance acidic emissions in the air. This creates the need for more pollution reduction efforts and circles back to the starting line.

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  • National Acid Precipitation Assessment Program Report to Congress (2005):
  • Acid Rain – Why It is a Concern (2004):


(1) Acid deposition is the deposit of gases and particles onto the earth’s surface in a wet or dry form. (2) pH refers to the basicity or acidity of a substance. On the pH scale, 7.0 is considered neutral. Anything higher is a base, and anything lower is acidic. (3) Buffering capacity is to the ability to counterbalance acidic compounds using other present elements so to stabilize the normal pH level. (4) Scrubbers are devices that chemically and physically remove sulfur compounds from coal combustion before they reach the atmosphere. These devices spray a limestone substance onto the burned coal. Lime, which is a neutralizing agent, encapsulates the sulfur particles so that they can be scooped away as a paste or powder product.
Submitted by Marisa on Jul 29, 2008