Acid rain is a broad term that includes any precipitation which has acidic components like sulfuric or nitric acid that fall from the atmosphere to the ground in the form of rain, snow, fog, hail or even dust. The acid rain containing water is known as wet deposition, while the acid rain with dust or gasses is called dry deposition. Normal rainfall is acidic with a pH of 5, but acid rain usually has a pH between 4. 2 and 4.4.
Scottish chemist Robert Agnus Smith for the first time used the term “acid rain” in 1852 while examining the chemistry of rainwater near industrial cities of England and Scotland. He wrote a book named Air and Rain: The Beginnings of a Chemical Climatology where he elaborated on his findings of the 1852 study. Smith is referred to as the “father of acid rain.”
Sources of Acid Rain
Acid rain is mostly an outcome of human activities. The greatest source of acid rain includes coal-burning power plants, oil refineries, industrial units, and automobiles. Burning of fossil fuel emits sulfur dioxide (SO2) and nitrogen oxides (NOx) to the atmosphere. These pollutants react with water, oxygen, and other substances and produce floating sulfuric and nitric acid compounds, which may spread through the air across the atmosphere over hundreds and thousands of kilometers.
When these compounds reach earth via rain, they flow into the rivers and oceans and other water system and sinks into the soil. The exhaust of cars, buses, and trucks also release sulfur and nitrogen dioxide into the air. Besides, deforestation and erupting volcanoes lead to the release of some chemicals that cause acid rain.
Formation of Acid Rain
Acid rain is formed when the sulfur and nitrogen compounds get dissolved with water and get carried by the wind and eventually become part of rain, snow, hailstorm, or fog.
In the United States, the power plants produce 70 percent of sulfur dioxide and around 20 percent of nitric oxide. The vehicles constitute 60 percent of nitric oxide emission in the country. The emissions contain nitrogen oxides, sulfur dioxide, and sulfur trioxide which when mixed with water become sulfuric, sulfurous acid and nitric acids.
In the year 1950, the scientists of the United States studied the phenomenon, and during the 1960s and 1970s, it affected Western Europe and eastern North America. It became recognized as a regional environmental issue.
However, recent studies have revealed that acid rain is no longer a local environmental issue. Over 90 percent of Norway’s acid pollution came from other countries of which Britain contributed about 16 percent. Other European countries contributing to acid pollution are Germany, Poland, the UK, and Spain. These nations are emitting millions of tons of sulfur every year, which are getting carried to other countries by wind and causing acid rains over there. Thus, acid rain is no more looked upon as a local issue, but as a severe global environmental problem.
Splendid Solutions of Acid Rain
Sulfur dioxide and nitrogen oxides do not constitute primary greenhouse gasses that cause global warming and climate change. On the contrary, sulfur dioxide cools down the atmosphere. However, it is nitrogen oxides that create harmful pollutant of ground-level ozone. Both the gases together affect the environment and lead to health concerns via air pollution and acid rain.
Acid rain has adverse effects on both the ecology and human civilization. After acid rain became recognized as a serious global environmental menace, many countries are contemplating a reduction in their amount of sulfur and nitrogen emissions.
Fighting the acid rain problem is a significant challenge. However, it is not an impossible task provided there is consorted effort from all the countries of the world. The solutions can include the following measures:
- Reduction in emission
- Looking for alternative sources of energy
- Resource conservation
- Restoring damages of acid rain
Reduction in Emission
In the United States, the Clean Air Act of 1990 is aimed at acid rain and puts a limit on sulfur dioxide emission. It targeted to lower the emission by 88 percent between 1990 and 2017. The air-quality standard of the country has also led to 50 percent curtailment in the nitrogen dioxide emission during the same period.
For lowering emission from vehicles, appropriate emission control devices must be used to remove harmful chemicals from the exhausts of cars.
Looking for Alternative Sources of Energy
So long as fossil fuel remains the primary source of energy, the problem of acid rain cannot be tackled effectively. Therefore, for prevention of acid rain, the search for alternative energy must be emphasized. Two most promising alternative sources of energy that have enormous potential are hydel and nuclear power.
Governments need to invest in researching different sustainable methods of producing energy. There are different sources of energy, and each has its benefits and costs. It is essential to weight them concerning the requirements of energy and their usage.
Governments also need to spend money on pollution control measures which should not include raising the price of electricity. Rather, supplying electricity using alternative energy sources.
There must be incentives for the use of public transport to minimize the usage of private cars and lower the emission level. Awareness needs to be created for efficient use of power and saving energy through the use of energy-saving appliances and power-saving practices like switching the lights off when one leaves the room. Encouraging people to walk shorter distances and use bicycles for local traveling. It can reduce the air pollution level while sharing cars can lessen emission.
Restoring Damages of Acid Rain
There is also a need for restoring the damages caused by acid rain. Lakes and rivers should be treated to neutralize their water. This is known as “liming” where powdered limestone is added to the water of rivers and lakes. However, this process is expensive and has temporary effects. Unless the acid rain is stopped, such practices will not be of much help. Economically developed countries like Norway and Sweden have successfully implemented liming to clear their water system and restore their status.
Recovering from the damage from acid rain takes time. The red spruce forests in New England, USA, and their fish population have recovered from the acid rain damage to a great extent. On the other hand, soils in the northeastern U.S. and eastern Canada have started showing signs of stabilizing nutrients in recent years after years of efforts.
The developing countries pose a significant problem when it comes to controlling pollution and acid rain. The huge population and high level of poverty of these countries lead to overexploitation of natural resources and raise pollution level with indiscriminate use of resources and nonadherence to standards.
Cities like New Delhi, India are one of the top five most polluted cities with staggeringly high sulfur dioxide and nitric acid components in the air. Countries like China depend heavily on fossil fuel to generate electricity and produce steel. They have turned out to be crucial sulphuric and nitric acid gas emission countries. It has been found that acid rain has caused a deadly landslide in China in the year 2009. While China has implemented control over its sulfur dioxide emissions, emission in India has increased by almost half.