Acid Deposition

By Elliott Strait

Chemical Processes

C O2(g) + H2 O(l) -> H2 C O3(aq)
Carbon dioxide reacts with water to create carbonic acid. This compound slightly lowers the pH of water.
3 N O2(g) + H2 O(l) -> 2 H N O3(aq) + N O(g)
Nitrogen dioxide reacts with water to create nitric acid. This compound greatly lowers the pH of water.
S O2(g) + H2 O(l) -> H2 S O3(aq)
Sulfur dioxide reacts with water to create sulfurous acid. This compound is even more acidic than nitric acid, and will immensely lower the pH of water.
2 S O2(g) + O2(g) + H2 O(l) -> 2 H2 S O4(aq)
Sulfur dioxide reacts with water to create sulfuric acid. This is the most acidic of the compounds, and is the most effective to the acidity of water.

When acid enters water sources, it will harm the nutrition of fish, causing them to die. Also, when the acid rain enters soil, the nutrients in the soil will move to the bottom of water sources, taking up space, and giving less space to wildlife.

Natural Processes

Acid rain will be created naturally by combining with CO2, NO, and SO2 found in the troposphere. Out of all the gases, carbon dioxide has by far the highest concentration. Because of this, carbon dioxide is the cause to the majority of rain's acidity. Carbon dioxide is created from the decomposition of organic matter, however, its high concentration isn't that big of a problem. Plants need carbon dioxide to survive and create oxygen, making it a necessity for life.

Nitric oxide is created when lightning combines nitrogen gas and oxygen gas. The nitric oxide then mixes with oxygen gas to form nitrogen dioxide. Finally, nitrogen dioxide mixes with rain water to create nitric acid, which raises the acidity of water. As for sulfur oxides, they are made from volcanic gases. These gases then mix with water in order to form sulfurous acid, or water and oxygen in order to form sulfuric acid, both of which are highly acidic, greatly raising water's acidity.

Anthropogenic Processes

Though there are many ways in which acid deposition may occur naturally, there are many ways that humans can affect it as well. For example, humans can create carbon dioxide from the burning of fuel in machinery. However, that is the least worrisome of anthropogenic sources of acid deposition. Human cars also create nitric oxide, and factories create sulfur dioxides. Compared to carbon dioxide, nitrogen and especially sulfur have an immense effect on the acidity to rain, and humans are releasing them into the air at astonishing rates.

Though we may be the cause of a large amount of rain's acidity, there is still good we can do as well. Because we are the source of the pollutants, it is simple for us to avoiding their use, such as not driving a car. Also, machines have technology inside of them designed to lower the amounts of pollutants expelled into the air. An example of this would be three way catalytic converters. These mix carbon monoxide and nitrogen dioxide and create carbon dioxide and nitrogen gas, and nitrogen gas can no longer react with water to create nitric acid.

The Good and Bad of Acid Deposition

Acid deposition has many different effects on the environment. However, is it overall beneficial or harmful to the environment? There are several topics in which to cover in order to determine this judgement. These topics would be that acid deposition has effects on methane production and life found in water and on land. These aspects together will have both beneficial and harmful aspects, but one will surpass the other.

First of all, large concentrations of acidity in rain water can slightly lower concentrations of methane gases in wetlands. Wetlands are home to many organisms, two of which play a large part in how much methane is released into the atmosphere. There are methane producing microbes in wetlands that compete for survival with archaea who feed off of concentrations of sulfur. When sulfuric acid is brought down to the earth due to rainfall, these bacteria are able to dominate over the microbes that create large quantities of methane. However, this is hardly that much of a benefit, as acid deposition does so much damage to life, that decaying corpses that have died from the rain release plenty of methane of their own.

It doesn't take a genius to know that acid being added to water will obviously make it more acidic. Upon doing so, life in the water will have trouble surviving, as the fish will die off from living in too low of a pH. The reason for this is because aluminum ions in aluminum hydroxide will be released when reacting with the acidic hydrogen ions from the rain. These aluminum ions then enter the respiratory system of the fish, causing them to die from lack of oxygen. This isn't the only problem that life in water must face. Nitrate ions from the nitric acid in the rain allow plants to grow rapidly, these plants then take the oxygen from the water, leaving none for the fish.

Finally, acid deposition can be insanely harmful to both plant and animal life on land. The acidity of rain water reacts with elements found in soil, such as magnesium, calcium, and sodium, and washes them into water supplies. Not only do these water supplies get polluted with excessive nutrients, but plants can no longer feed off of nutrients originally found in the soil. Nutrients like magnesium are needed for plants to photosynthesize, when it's washed out, the plants starve. Also, the aluminum hydroxide mentioned in the previous paragraph will pass through the soil and damage the roots of plants. Worst of all, plants are the begging of the food chain, as they die off, so does the rest of life.

Acid deposition, though it may reduce methane production in some cases, causes insane damage to the environment. It is therefore by all means harmful to our environment. The human race should take any and all precautions necessary to end polluting. Acid deposition is only one of its many effects, there are still many other downsides to polluting, such as ozone depletion. Just because humans aren't the only source of acidity in the rain water, by no means does that mean that they cannot do something to help.

Extra Credit Video

What is acid rain? // Chemistry II


Casiday, Rachel, and Regina Fey. "Acid Rain." Department of Chemistry. Washington University, n.d. Web. 08 Dec. 2014.

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Brown, Catrin. Higher Level Chemistry: Developed Specifically for the IB Diploma. N.p.: Pearson, 2009. Print.

DIMY Barboza. "What Is Acid Rain? // Chemistry II." YouTube. YouTube, 09 June 2013. Web. 11 Dec. 2014.