We explain what acid rain is, the causes of its formation and its various effects. Also, what are its features and solutions.
What is acid rain?
Acid rain is a type of precipitation that has higher acidity than normal. The acidity of substances is measured through the pH, which can vary between 0, for the most acidic substances, and 14 for the most basic substances. A substance with pH 7 is a neutral substance.
Common rain has a slightly acidic pH: 5.6. This pH value is due to the natural presence of carbon dioxide (CO2) in the atmosphere, which forms carbonic acid (H2CO3) in contact with air humidity.
For rain to be considered acidic, it must have a pH less than 5.. In some cases, precipitation has been observed that even reaches pH 3, a value well below normal parameters (it is, for example, the approximate pH of vinegar).
Although acid rain can occur as a consequence of natural phenomena, such as volcanic eruptions, in recent years atmospheric pollution has multiplied the presence of this type of rain in many places around the world.
- See also: Greenhouse effect
Causes of acid rain
Acid rain is caused by the presence of sulfur dioxide (SO2), sulfur trioxide (SO3) and oxides of nitrogen (NxEITHERand) in air humidity. Most of these substances come from human activities that use fossil fuels, such as thermal energy generation, industry and transportation.
Forest fires can contribute to the formation of acid rain. When forests burn, large quantities of gases such as carbon dioxide, carbon monoxide, nitrogen oxide, sulfur and other volatile organic compounds are emitted.
Once these gases are released into the atmosphere, they can react with other atmospheric pollutants such as nitrogen oxide or sulfur dioxide to form sulfuric acid and nitric acid, which then precipitate to the surface as acid rain.
On the other hand, acid rain can occur, to a lesser extent, by natural sources such as volcanic eruptions. During a volcanic eruption, large quantities of sulfur dioxide, nitrogen oxides, hydrochloric acid and hydrofluoric acid, among other gases and particles, are released.
Sulfur dioxide released in a volcanic eruption reacts with water vapor in the atmosphere to form sulfuric acid, while nitrogen oxides can react with other atmospheric compounds to form nitric acid. These acids can then fall to earth in the form of acid rain.
How is acid rain formed?
Acid rain forms when nitrogen oxides, sulfur dioxide, and sulfur trioxide mix and react with water in the atmosphere to form nitric acid (HNO).3) and sulfuric acid (H2SW4).
These acids mix with the moisture contained in the atmosphere in the form of water vapor and then precipitate mixed with rainwater.
Primary pollutants are substances that are emitted directly into the atmosphere such as sulfur dioxide, nitrogen oxides and volatile organic compounds, among others. These pollutants can react with other compounds in the atmosphere such as water, oxygen and other gases, to form secondary pollutants, such as sulfuric acid and nitric acid, which are the main components of acid rain.
Sulfur dioxide, carbon dioxide and nitrogen oxides come into contact with air humidity, atmospheric oxidants and sunlight. Then, chemical reactions occur between these components that generate sulfuric acid and nitric acid, which are the chemical compounds that make up acid rain.
Some of the chemical reactions involved in the formation of acid rain are:
Formation of sulfur dioxide (SO2)
By reaction of sulfur (S) and molecular oxygen (O2). Sulfur can be generated from emissions of dimethyl sulfide (CH3)2S or hydrogen sulfide (H2S).
- S+O2 → OS2
Formation of sulfurous acid (H2SW3)
From sulfur dioxide (SO2) and water (H2EITHER).
- SW2 +H2O → H2SW3
Formation of sulfur trioxide (SO3)
From the reaction between sulfur dioxide (SO2) and molecular oxygen (O2).
- 2SO2 +S2 → 2SO3
Formation of sulfuric acid (H2SW4)
From sulfur trioxide (SO3) and water (H2EITHER).
- SW3 + h2EITHER → h2SW4
Formation of nitric acid (HNO3)
From the reaction between nitrogen dioxide (NO2) and water (H2EITHER).
- 3NO2 + h2EITHER → 2HNO3 + NO
What regions are affected by acid rain?
The main regions of the world that suffer the effects of acid rain are those that have the highest emissions of polluting gases.
- Central and Eastern Europe. It has suffered the effects of acid rain since the 1960s due to sulfur and nitrogen emissions from the burning of coal and oil in power plants. Germany, Poland and Romania are some of the most affected countries.
- Northeast North America. The Great Lakes region in the United States and southern Canada also suffer the consequences of acid rain as a result of the polluting industries installed in the region.
- East Asia. China, Taiwan, South Korea and Japan have experienced a significant increase in acid rain events in recent decades due to their rapid industrialization.
- Areas near volcanoes. Some countries such as Indonesia, the Philippines and Mexico have experienced acid rain events as a result of eruptions of the Merapi (Indonesia), Pinatubo (Philippines) and Colima (Mexico) volcanoes, among others.
Consequences of acid rain
Effects on aquatic ecosystems
In China, pollution is very significant because 70% of electrical energy is obtained from burning coal.
The other countries most affected are those located further north in the northern hemisphere: Holland and other Nordic European countriesUnited Kingdom, United States and Canada.
Effects on aquatic animals
Acid rain lowers the pH of water in lakes, rivers and oceans.which can have negative effects on the organisms that live in these aquatic ecosystems. Lower pH can damage fish gillsand this can cause breathing difficulties and other alterations in your organic functioning.
Additionally, acidification can decrease the water's ability to store oxygen, which can also lead to the death of fish and other aquatic organisms.
Acid rain can also harm plants and invertebrates that live in water. Plants can suffer damage to their leaves, due to the difficulty in carrying out photosynthesis.. For their part, invertebrates (such as snails and aquatic insects) are also affected by the decrease in water pH, which generates negative effects on their growth and reproduction.
- It may help you: Water pollution
Effects on humans
Acid rain can have negative effects on human health. When you breathe the acids that this type of rain brings, These pollutants can reach the lungs and cause respiratory problems. Prolonged exposure to these gases can also increase the risk of developing heart disease.
Furthermore, humans can consume foods, both of plant and animal origin, that contain toxic substances absorbed through soil or water and this can also represent a risk to their health.
The same happens with the consumption of water contaminated by acid rain gaseswhich can cause gastrointestinal diseases and kidney damage
Effects on soil and plants
Soil acidification causes the release of toxic metals that make it difficult for plants to absorb nutrients. In addition, acid rain can affect the microorganisms present in the soil and dissolve its nutrients, which impoverishes its quality and fertility.
Finally, it can damage leaves and plant tissues, weakening them and making them more susceptible to diseases and pests.
- It may help you: Soil pollution
Effects on the economy
Various sectors of the economy are affected by the consequences of acid rain.
The most affected sector is agriculture. This activity may see its production decreased, since Without the necessary nutrients in the soil, plants do not achieve the necessary growth.which can significantly reduce production and profit margins. In addition, the reduction in the production of some agricultural raw materials can impact the increase in food prices.
Another sector directly affected is fishing and fish farms, since the effects on the reproduction of specimens and water quality reduce production and profit margins.
Effects on architecture
In addition to being a danger to living beings, Acid rain causes corrosion in the materials of buildings, bridges and pipes.
For example, monuments or buildings made of limestone or marble are especially vulnerable to the corrosive effects of acid rain. The acids in these rains dissolve calcium carbonates, leaving monuments and buildings with a rough surface and a discolored appearance.
Possible solutions for acid rain
One of the solutions that some governments and states are implementing is the application of new protocols to reduce the emission of sulfur dioxide and nitrogen oxide from various industries.
Vehicle emissions are also a major source of nitrogen oxides.. For this reason, the governments of many countries are implementing policies to control vehicle emissions and promoting the use of more sustainable transport units.
- ecological footprint
- Environmental impact
- Drought
- Volcanoes
- Natural disasters
References
- Juste, I (2022). Acid rain: definition, causes and consequences. Green ecology. https://www.ecologiaverde.com/
- Montalvo, F. and Escobar, D (2011). Acid rain of volcanic origin. National Territorial Studies Service.
- National Geographic (2023). What is acid rain and why does it occur? https://www.nationalgeographic.es/
- Granados Sánchez, D. López Ríos, GF and Hernández García, M. Á (2010). Acid rain and ecosystems forestales. Chapingo Magazine forestry and environmental sciences series. On-line version ISSN 2007-4018. Printed version ISSN 2007-3828
