Acid rain, also known as acid precipitation or acid deposition, is the precipitation with a pH of 5.2 or below that is mostly caused by human activities such as the combustion of fossil fuels, which emit sulfur dioxide (SO2) and nitrogen oxides. Acid deposition can impair biodiversity and lower the pH of surface waters in acid-sensitive areas. It weakens trees and makes them more vulnerable to other stressors such as drought, extreme cold and pests.
What is acidity?
The concentration of hydrogen ions (H+) in a solution is defined as acidity. The pH scale determines how acidic or basic a solution is. Below the pH of 7, substances are considered acidic, and each unit of pH below 7 is 10 times more acidic, or contains 10 times more H+ than the one above it. Rainfall with a pH of 5, for example, has 10 micro-equivalents of hydrogen per liter, whereas rainwater with a pH of 4 contains 100 micro-equivalents of hydrogen per liter.
Is normal rain acidic?
Because of the absorption of carbon dioxide (CO2) from the atmosphere, normal rainfall is slightly acidic. In addition, depending on the emissions associated with individual volcanoes, volcanic activity can produce sulfuric acid (H2SO4), nitric acid (HNO3) and hydrochloric acid (HCl). The creation of nitrogen oxides from the conversion of air molecular nitrogen (N2) by lightning and the conversion of organic nitrogen by wildfires are two more natural sources of acidity.
What is Acid Rain?
Acid rain or acid deposition, is a general phrase that refers to any type of precipitation that contains acidic components, such as sulfuric or nitric acid, and falls to the ground in wet or dry form, from the atmosphere. This can include acidic rain, snow, fog, hail, or even dust.
Causes of acid rain
Acid rain is caused by the pollution in the atmosphere. When sulfur dioxide and nitrogen oxides are released into the atmosphere and carried by wind and air currents, acid rain occurs. Sulfuric and nitric acids are formed when SO2 and NOX combine with water, oxygen and other molecules. After mixing with water and other things, they fall to the earth. This explains formation of acid rain.
While some of the SO2 and NOX that create acid rain come from natural sources like volcanoes, the majority of it comes from the combustion of fossil fuels. When any form of fuel is burned, a variety of chemicals are released. Smoke from a fire or fumes from a car exhaust contain more than just the obvious sooty grey particles. They also contain a variety of unseen gases that can be far more detrimental to our environment.
Because power plants, industry, and automobiles all consume fossil fuels, they all emit damaging gases. Sulphuric and nitric acids are formed when some of these gases combine with the tiny droplets of water in clouds. The rain that falls from these clouds is very weak acid, which is why it is called acid rain.
Here are the principal sources of SO2 and NOX in the atmosphere:
- To generate power, fossil fuels are burned. Electric power generators are responsible for two-thirds of SO2 and one-fourth of NOX in the environment.
- Vehicles and heavy machinery
- Manufacturing, oil refineries, and other industries are just a few examples.
Acid rain is an issue for everyone, not just those who live near these sources, because wind may carry SO2 and NOX across great distances and across borders.
Forms of Acid rain
Acid rain is most typically associated with wet deposition. Sulfuric and nitric acids generated in the sky mix with rain, snow, fog or hail to fall to the ground.
In the absence of moisture, acidic particles and gases can settle as dry deposition from the atmosphere. Acidic particles and gases may swiftly settle on surfaces or react with larger particles in the atmosphere, posing a threat to human health. When stored acids are washed off a surface by the next rain, acidic water pours over and through the ground, harming plants and wildlife including insects and fish.
The quantity of acidity in the atmosphere that falls to earth as a result of dry deposition is determined by the amount of rain that falls in a given area. Desert locations have a larger ratio of dry to wet deposition than areas that receive several inches of rain each year.
Acidity of acid rain
The pH scale is used to determine how acidic something is. This scale ranges from 0 to 14, with 0 being the lowest and 14 being the highest. The most acidic is 0 while the most alkaline is 14. We call something with a pH of 7 neutral, which indicates it is neither acidic nor alkaline.
What are the effects of acid rain?
Acid rain has a wide range of biological consequences, particularly for lakes, streams, wetlands, and other aquatic ecosystems. Acid rain increases the acidity of such waterways, causing more aluminum to be absorbed by the soil and transferred into lakes and streams. Crayfish, clams, fish, and other aquatic species are poisoned by this combination. Forests and fish are dying all across the world. There are dead lakes in Scandinavia that are crystal clean and devoid of any live organisms or plant life. As a result, fish-eating birds and animals are also affected. Forests, particularly those at higher elevations, are also harmed by acid rain and fog. Acid deposits deplete essential nutrients like calcium and cause aluminum to be released into the soil, making it difficult for trees to absorb water. Acids also injure the leaves and needles of trees.
Acid rain can travel long distances in the atmosphere, not only across countries but also between continents. Snow, mists and dry dusts are all examples of acid. Rain can fall many miles from the source of pollution, but it can have a significant impact on soil, plants, and buildings and water wherever it lands.
Acid rain depletes soil of key plant nutrients and buffers, such as calcium and magnesium. It causes the degradation of limestone and marble buildings and monuments by contributing to the corrosion of surfaces exposed to air pollution. It is a common name for the more technical term acid deposition, which refers to the various ways acidity can travel from the atmosphere to the Earth’s surface. Acid rain, as well as other types of acidic wet deposition such snow, sleet, hail and fog are examples of acid deposition. Dry deposition of acidic particles and gases, which can impact landscapes during dry periods, is also referred to as acid deposition. As a result, even when there is no precipitation, acid deposition can have an impact on landscapes and the living beings that inhabit them.
Why is acid rain harmful?
If really strong acids come into contact with your flesh, they will burn you and can even destroy metals. Acid rain is a lot weaker than this, and it will never burn your flesh. Because it combines with naturally occurring oxides in the air, rain is usually slightly acidic. The pH of unpolluted rain would be between 5 and 6. However, the acidity of the air can rise to a pH of 4 when it is polluted with nitrogen oxides and sulphur dioxide. Some rain has even been found to have a pH of 2. Lemon juice has a pH of 2.3, while vinegar has a pH of 2.2. Even the most acidic acid rain ever recorded is just approximately as acidic as lemon juice or vinegar, and we know that neither of these are harmful to us, so we should not be concerned about acid rain. But one should not feel completely relaxed from it, as it can destroy trees, forests, lakes and underwater animals.
How to prevent acid rain?
The only approach to combat acid rain is to reduce the amount of pollutants released into the atmosphere. This entails using fewer fossil fuels and establishing air-quality guidelines.
- The government should provide more incentives to public transportation to encourage people to use it instead of driving.
- Everyone can help save energy by turning off lights when they are not in use and using energy-efficient equipment; when less electricity is used, pollution from power plants is reduced.
- Walking, cycling, and carpooling all help to reduce vehicular pollution.
- Liming is the process of adding powdered limestone to lakes and rivers to neutralize the water. Liming is costly and has only a brief impact; it must be repeated until the acid rain ceases. Liming has been employed successfully by the people of Norway and Sweden to help restore lakes and streams in their respective countries. Wales is currently undergoing a large liming effort.