All rain is acidic to some degree. When rainwater is combined with carbon dioxide that is dissolved, it produces a very weak acid called carbonic acid. This combination is no real threat to our environment but the sulfuric and nitric acid that comes from pollution and distributed through the rainwater does cause harmful effects to the environment and to all living things.
To find out how acid rain is produced, you can examine pieces of coal that contain sulfur. You will find yellow, powdery streaks, which is the sulfur.
When burned, the coal combines with oxygen to form sulfur dioxide, which is then oxidized in our atmosphere to sulfur trioxide and when this gas mixes with the rain, dilute sulfuric acid is then formed.
In our air, nitrogen is present and makes up about 79% of the dry air, and is usually a non-reactive gas. In a car’s internal combustion engine, the conditions are perfect for nitrogen and oxygen to mix which forms nitrogen oxides.
Many different oxides of nitrogen exist, the term Nox gases are used, which then dissolve in the rainwater and form nitric acid.
A major source of emissions of nitrogen oxides in the air is from vehicles and other places where fossil fuels are burned. Forest fires that are often started by humans are other sources of pollution.
Naturally occurring events, such as volcanic activity, lightning, or organic decay also cause an increase in the atmospheric pollutants and over 90% of sulfur dioxide emissions and 95% of nitrogen oxides that are released into our atmosphere are from humans.
Acid rain was first noticed in the seventeenth century, when people started noticing the effects of industrialization on plants and animals. As far back as 1872, Angus Robert Smith, a Scottish chemist wrote a book called “Air and Rain: The beginnings of Chemical Climatology”, (Smith, 1872) and he used the term “Acid Rain”, and the name has been used ever since that time.
The problems of rain have severe since the 1960’s when fisherman started noticing a huge reduction in the amount of fish present in the North American and European lakes.
The emissions may travel over long distances and for many days, and the wind and climatic conditions are very important and determines where the acid rain will then fall.
Acid rain affects crops, such as natural vegetation. The roots are damaged by the acid rainfall, and it causes the plant growth damage, where the plant is stunted or even killed. The acidity causes the nutrients in the soil to be destroyed.
Micro organisms, which release from decaying organic matter, into the soil are destroyed and result in fewer nutrients that are available for the plants. The acid rain that falls on the plants then mars the waxy layer on the leaves and the plant is then susceptible to disease. Even if the plant survives, it will remain extremely weak and will be unable to live through poor weather conditions, such as heavy rainfall, strong winds or short dry periods.
Plant germination and reproduction is also inhibited by the bad effects of acid rain.
Plants, animals, humans and even buildings and other structures are affected by acid rain. Paint from building, in the cities has peeled away and the color on automobiles has faded due to acid rain.
In some parts of Poland, trains must run slowly because the train tracks are so severely damaged due to acid rain.
“Acid Rain”, a book by Steve Elsworth, (Elsworth, 1984) tells us that “there are many things that we can do to limit acid rain. “ Environmental regulations have been enacted to limit the emissions released in the atmosphere, to try and end some of the high acid consistence in the rain, as a form of prevention.
There are several industries who have added scrubbers to their smoke stacks to limit the amount of sulfur dioxide in the atmosphere. Catalytic converters that are specially designed to make sure that the gases released from exhaust pipes are harmless are being used, which is very helpful. Many industries that use coal as fuel are starting to wash the coal before use, to reduce the amount of sulfur in the coal.
There are many descriptions of acid rain and the one that is offered in Dictionary.com, tells us that acid rain is precipitation, as rain, snow, or sleet, containing relatively high concentrations of acid-forming chemicals, as the pollutants from coal smoke, chemical manufacturing, and smelting, that have been released into the atmosphere and combined with water vapor: harmful to the environment.
With all the harmful effects of acid rain on the environment, it is pretty surprising that acid rain can actually be considered beneficial. Sulfates in the upper atmosphere reflect some sunlight out into space, and tend to slow down global warming.
Scientists believe that acid pollution may have delayed the onset of warming by several decades in the middle of the twentieth century.
College of Agricultural Sciences, (News Release Archive, 1999), showed that in the past 20 years for which records are available, Pennsylvania received some of the most acidic rain in North America. As a result, our forests have changed profoundly, says a forest hydrologist in Penn State’s College of Agricultural Sciences.
“Acid rain is a problem that is both severe and widespread in Pennsylvania,” says professor of forest hydrology. “Available long-term soils and fisheries data are evidence that the problem is a huge concern.”
Sharp believes a recent decline in two economically important trees–the northern red oak in Laurel Hill and the sugar maple in the Allegheny National Forest and the Susquehannock State Forest–is caused by soil acidification that results from the acid in the rain.
Trees are harmed by acid rain in many ways. When the waxy leaves on the trees, just like the plants, the nutrients are lost, and it makes the trees more susceptible to frost, fungi and insects. Root growth is then slowed down and as a result, fewer nutrients are taken up. Toxic ions are mobilized in the soil, while vulnerable minerals are leached away and bound to aluminum or iron compounds, or to clay.
The toxic ions that are released, due to acid rain form the greatest threat to humans. Mobilized copper has been implicated in outbreaks, causing illness in children and it is questioned whether it has contaminated the water supplies and may cause Alzheimer’s disease.
Erosion can also be caused by acid rain, on old and very valuable structures, such as statures and has caused damage to the structures. The sulfuric acid in the rain chemically reacts with the calcium in the stones and creates gypsum, which flakes off. It is commonly seen on old gravestones, as well, because the acid rain caused the inscriptions to become unreadable.
“Acid Rain”, (Gay, 1983), a book written by Kathlyn Gay talks about some of the harmful effects of acid rain on our environment.
Acid rain can also cause harmful effects to books. The acidic gases in the air break down the cellulose and cause the paper to become fragile and after time, it will crumble to dust. This problem means that the world’s greatest libraries must protect their rare books, which costs a great amount of money to preserve them.
There are many studies being done, in order to reduce the amount of acid in our rainwater.
It is extremely important that we all do our part in controlling the acid in our rainwater and it is important that we make sure big industries continue to take measures which reduce sulfur into our atmosphere.
Smith, Angus Robert. Air and Rain. London, Longmans, Green and C. 1872.
Elsworth, Steve. Acid Rain. London: Pluto Press. 1984
Dictionary.com. Unabridged, Volume 1.1. Random House. 2006
Gay, Kathlyn. Acid Rain. New York: Watts. 1983
News Release Archive. College of Agricultural Sciences. New Books From Penn State
Present Findings on Acid Rain. 199