- When the rainwater has a pH below 5, it becomes acidic
- Acid rains are formed when acid-producing gases react with water in the atmosphere
- Acid rains can happen in nature because of lightning strikes, forest fires and volcanic eruptions
- Human activity also causes acid rains to happen – due to emissions from factories, burning of fossil fuels, exhaust from transport and releasing chemical waste into the soil and water
- Acid rains are a serious problem and are frequent in Western Europe, North America and some regions of Asia
- Acid rains cause death of animals and plants in the seas, rivers, on land and in the soil
- They also cause significant damage to human health
- One can prevent acid rains by using cleaner energy sources, means of transport and improved methods of waste disposal
Anyone who has ever skimmed the Bible has probably read about the terrifying rains, sent as a punishment from the heavens. In these stories, fire was falling from the heavens, together with liquids that could dissolve anything. This picture seems to be something from a dystopian fantasy – yet such dangerous rains were a reality in our deep past. Moreover, they are a modern problem as well.
As you may know, one of the important chemical characteristics is pH. pH means the quantity of H+ protons in a substance. The pH of pure water without additives is 7. A substance that has low pH, from 7 to zero, is called acidic. For example, a strong acid such as hydrochloric acid has a pH around 1. If the pH is more than 7, the solution is alkaline. For example, bleach has a very high pH, around 13,5.
The rain that falls on our heads is not really pure water. It is slightly acidic and has a pH of 6.0-5.3 because of various substances that the rain takes up. But sometimes the pH of the rain shifts dramatically.
This phenomenon was first discovered by a Scottish chemist named Robert Angus Smith in the year 1852. He has discovered that the rain that falls in the area of Manchester, a big industrial town, has significantly lower pH than normal. He has coined the term “acid rain”. At this time, factories actively used coal, and there was smoke everywhere. This smoke pollution caused fogs and people had difficulty breathing. And, as Smith has discovered, it probably was also causing acid rains, too.
Times have changed. Coal became less widespread, but our plants and factories began using fossil fuels such as oil and gas instead. People have invented cars that run on gasoline. And around 1970s, the scientists confirmed that acid rains were still a reality. Moreover, they became a very serious ecological problem, damaging buildings, making people ill and bringing destruction to seas and forests. Acid rains became a topic of active research, and scientists have found out that there are many causes of it. Unfortunately, those causes are usually human-related.
Natural causes of acid rain
1. Volcanic eruptions.
When volcanoes erupt, they release multiple things: magma, hot coals and gases. These gases are acid-producing. They rise up into the atmosphere, become part of the water vapor clouds and then condensate, forming acid rain.
Sometimes, extreme heat or a lightning strike causes a forest fire to erupt. Large territories can be affected, and the smoke rises to the skies. This smoke also produces acids and can contribute to acid rainfalls
3. Lightning strikes
The temperatures in the area where lightning strikes are very high. These increase in temperature causes the nitrogen and oxygen atoms to react, forming nitric oxide (NO). The oxide, in turn, reacts with water, producing nitric acid. And this acid also can fall in the rain form to the earth.
Thankfully, it is not a concern at present, but many millions years ago, asteroids were a huge problem for life on our home planet. The fall of the asteroids caused great changes in the environment. Their speed and weight used to hit the land so strongly that huge clouds of dust particles rose and stayed in the atmosphere for a long time. According to the paleontologists, the acid rains formed as a result were so dangerous that they could literally melt stones. No wonder asteroids were major causes of extinctions in course of evolutionary history.
As you can see, most natural causes of acid rains are not very frequent. Volcanic eruptions, for instance, are quite rare. Yet acid rains were detected in many places and are presently a significant problem in North America and Western Europe. And the reason for this is the human activity.
Why Human Activity Causes Acid Rains?
Since Industrial Revolution in the middle of 19th century, humans have been using a lot of fossil fuels to produce multiple things. Multiple new materials were invented, such as plastic and various cleaning powders. Cars, trains, airplanes and ships running on various fossil fuels started crossing the world. But all this activity produces a lot of waste. The emissions of carbon dioxide, sulfur dioxide and nitrogen dioxide are steadily released into the atmosphere from vehicles and factories. These substances react in the atmosphere with water, producing acids that fall as rain. Another danger is the fact that many industries release their waste into the rivers and the seas. This poisoned water evaporates and returns to us in form of rain, too. As a result, depositions of acid are found in Western Europe, around North America and even in some parts of Asia.
Acid rains are extremely dangerous. Let us look at possible consequences:
1. Danger to the marine and freshwater ecosystems
When acids get into the water, they change its pH. Most fish are used to a certain pH. If it changes, they get sick and their eggs cannot hatch. Algae and small invertebrates also can die in acidic environments. If the acidity increases too much, all life in a pond or a lake can completely die. In the seas, the increased concentration of acids can cause the death of corals, fish and other creatures.
2. Poisoning the soil
If acidic rainwater gets into the soil, it can wreak havoc there. It changes the environment for soil bacteria that fix nitrogen for plants and decompose dead matter. It can kill multiple microscopic organisms living in the soil. Plants that are forced to grow in such acidic soil, begin to fall ill. In extreme cases, the land becomes dead and infertile.
3. Damage to the plants and animals
Contact with acids can directly injure plants and animals. It can cause illnesses in plants, burns and breathing problems in animals.
4. Damage to the human health
In humans, acid rains can cause damage to the skin, allergic reactions, damage to the lungs and overall well-being. If people eat plants covered with acid, they can get severely ill as well. Another danger is destruction of wild plants, crops and cattle, as well as extinction of freshwater fish.
5. Damage to the buildings
Acid is corrosive. It destructs metal and can even cause erosion in rocks. Consequently, acid rains not only damage living beings – they also destroy buildings made by humans.
Can We Prevent Acid Rains From Happening?
We can, a least in part! The first step in our fight against acid rains is done – people have acknowledged the problem. Acid rains are not a myth, but a present-day danger. We can decrease the appearance of acid rains if we:
1. Use alternative sources of energy
Experiments in Scandinavia and Germany have proven that it is quite possible to generate electricity with the help of alternative sources of energy: sun batteries, wind electrical stations and water energy. Such sources do not generate carbon dioxide or other kinds of acid-producing toxic wastes.
2. Use better means of transport
At present, there are cars that have good filters that do not produce as much exhaust. Many people also begin actively using electric cars. And bikes are also becoming increasingly popular. They are helping people become stronger and healthier, too!
3. Use filters at the plants factories
Presently, there are powerful filters that prevent toxic substances from going up with the smoke. They can greatly reduce the quantity of acid-producing gases.
4. Invent new method of waste disposal
Burning garbage is the worst way to dispose of it. Previously, the garbage just smelled bad and made you uncomfortable. By burning it, you are potentially poisoning yourself, your neighbors and all the animals and plants around. Thankfully, there are better methods being developed, using bacteria, plants and even earthworms. Hopefully, there would be new, better and safer methods of garbage destruction in the near future. And hopefully new laws would prevent the chemical factories just pour their waste in our rivers and seas.
It is possible that you will never encounter an acid rain in your area. But by being mindful of the environment, you can make your own contribution to preventing acid rains.
Links and further reading:
[1.] What Is Acid Rain? (n.d.) Conserve Energy Future. https://www.conserve-energy-future.com/causes-and-effects-of-acid-rain.php