Acid rain

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Acid rain


  • formation of acid rain
  • effects and effects of acid rain
  •   acid rain mitigation
  • Society’s role in combating acid rain 

An analysis of ice cores from Greenland indicated that anthropogenic sulfate has dominated sulfur deposition since the early twentieth century and anthropogenic nitrate has dominated nitrogen deposition since about 1960.

Acid rain is an invisible environmental threat to society. The term acid rain was first coined by the British chemist Robert Angus Smith in 1852 to describe the high acidity of rain due to the presence of sulfuric acid due to fumes from the burning of coal in Liverpool, Glasgow and other British industrial centres. , Smith estimated the various effects of acid rain on trees and crops and the corrosion of metals. In the 1950s, Avril Gorham, a Canadian ecologist at Dalhousie University, came across Smith’s work and documented the effects of acid rain in English Lake and around the Inco nickel mining smelter located in Sudbury, Canada. The acid rain debate spread to the United States in 1974 when Likens and Borman’s work was published in the journal Science. The environmental problem of acid rain has become a very important pollution problem of the present time.


This rainfall is recognized as a global and a trans-boundary environmental problem. Areas most affected are areas with coal-fired power plants, smelters or factories, or major urban areas with large numbers of motor vehicles, e.g. Acidic emissions from industrial areas in Western Europe (particularly the United Kingdom and Germany) and Eastern Europe blew into Norway, Switzerland, Austria, Sweden, the Netherlands, and Finland.

The worst acid deposits are in Asia, especially China, which gets about 59 percent of its energy from burning coal. According to scientists’ estimates, by 2025, China will emit more sulfur dioxide and carbon dioxide than the United States, Canada and Japan combined.



Acid rain is the term for the atmospheric deposition of acidic substances. Acidic substances are deposited not only by rain and other types of moist air but also in the form of dry particles.

Precipitation is normally mildly acidic, with an average pH of 5.0. pH is the measurement for acidity, the lower the number, the more acidic the substance, with 7.0 being the divide between acidity and alkalinity.



formation of acid rain

Acid rain precursors originate from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily from emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) resulting from fossil fuel combustion. acid rain occurs

When these gases react with water, oxygen and other chemicals in the atmosphere

various acidic compounds. The result is a mild solution of sulfuric acid and nitric acid. When sulfur dioxide and nitrogen oxides are released from power plants and other sources, prevailing winds blow these compounds across state and national boundaries, sometimes hundreds of miles.



Wet deposition refers to acid rain, fog and snow. When acid chemicals in the air are blown over areas where the weather is wet, the acid can fall to the ground in the form of rain, snow, fog or mist. As this acidic water flows above and below the ground, it affects a wide variety of plants and animals. The strength of the effects depend on several factors, including how acidic the water is; the chemistry and buffering capacity of the soil involved; and fish, trees, and other living things that depend on water.



  dry freeze

In areas where the weather is dry, acid chemicals can become incorporated into dust or smoke and fall to the ground through dry deposition, sticking to the ground, buildings, houses, cars and trees. Dry deposited gases and particles can be washed from these surfaces by rainstorms, increasing runoff. This runoff water makes the resulting mixture more acidic. About half the acidity of the atmosphere falls back to the earth by dry deposition.

  effects of acid rain

effects on human health

Acid rain—sulphur dioxide (SO2) and nitrogen oxides (NOx) producing pollutants harm human health. These gases combine in the atmosphere to form microscopic sulfate and nitrate particles that can be carried by the wind over long distances and can be carried deep into people’s lungs. Fine particles can also enter indoors. There have been many scientific studies

identified an association between elevated levels of fine particulate matter and increased disease that contribute to human respiratory disease such as bronchitis and asthma. It can leach out toxic metals like lead and copper

, Drinking water from water pipes causes many diseases.


  effects on property and materials

Acid rain and the dry deposition of acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration of paint and stone (such as marble and limestone). These effects significantly reduce the social value of buildings, bridges, cultural objects (such as statues, monuments and tombs). For example, the Parthenon in Greece and the Taj Mahal in India have been affected by acid rain.



Effects on Aquatic Ecosystem

The ecological effects of acid rain are most clearly seen in aquatic, or water, environments, such as streams, lakes, and marshes. Acid rain flows into rivers, lakes and swamps after falling on forests, fields, buildings and roads. Acid rain also falls directly on aquatic habitats. Most lakes and streams have a pH between 6 and 8, although some lakes are naturally acidic even without the influence of acid rain. Acid rain mainly affects sensitive bodies of water, located in watersheds, which have a limited capacity to neutralize acidic compounds in the soil (called “buffering capacity”). Lakes and rivers become acidic (i.e., the pH value goes down) when the water itself and the soil around it are unable to buffer acid rain sufficiently to neutralize it. In areas where buffering capacity is low, acid rain releases aluminum from the soil into lakes and streams; Aluminum is highly toxic to many species of aquatic life. Acid rain causes a cascade of effects that harm or kill individual fish, decimate fish populations, eradicate fish species altogether, and reduce biodiversity. Makes it Some types of plants and animals are able to tolerate



Acidic water. Un

They are, however, sensitive to acid and will be lost as the pH drops. Generally, the young of most species are more sensitive to environmental conditions than the adults. At pH 5, most fish cannot spawn. At low pH levels, some adult fish die. Some acid lakes do not contain fish.



  Effects on Soil and Plants

Rain in the forest washes the leaves and falls through the trees to the forest floor below. Some water drips onto the ground and runs into streams, rivers, or lakes, and some seeps into the soil. Soil can neutralize some or all of the acidity of acidic rainwater. This capacity is called the buffering capacity and without it the soil becomes more acidic. Differences in the buffering capacity of soils are an important reason why some areas that receive acid rain show much damage, while other areas that receive roughly the same amount of acid rain show no damage at all.


The ability of a forest to resist or buffer soil acidity depends on the thickness and composition of the soil as well as the type of rock beneath the forest floor. Acid rain usually does not kill trees directly. Instead, trees are more likely to be weakened by damage to their leaves, by limiting the nutrients available to them, or by exposure to toxic substances that are slowly released from the soil. Often, these effects of acid rain in combination with one or more additional hazards result in tree injury or death.

Research shows that acidic water dissolves nutrients and helpful minerals in the soil and then washes them away before trees and other plants can grow. At the same time, acid rain causes the release of substances that are toxic to trees and plants, such as aluminum, into the soil. Scientists believe that this combination of soil nutrient loss and an increase of toxic aluminum may be one way acid rain damages trees. Such substances are also washed away in runoff and carried into streams, rivers and lakes. When the rain is more acidic, more of these substances are released from the soil.

However, trees can be damaged by acid rain even if the soil is well buffered. Forests in high mountain regions are often exposed to higher amounts of acid than other forests because they are surrounded by acidic clouds and fog which are more acidic than rain. It is believed that when the leaves are repeatedly bathed in this acidic fog, their leaves and needles are stripped of essential nutrients. This loss of nutrients in their foliage makes the trees more vulnerable to damage from other environmental factors, especially cold.

Acid rain can harm other plants in the same way that it harms trees. Although damaged by other air pollutants such as ground-level ozone, food crops are usually not severely affected because farmers often add fertilizer to the soil to prevent nutrients from being washed out. They can also add crushed limestone to the soil. Limestone is an alkaline material and enhances the soil’s ability to act as a buffer against acidity.



Acid rain control measures

The control of acid deposition is a regional problem and a complex political problem for three basic reasons:

First, populations and ecosystems are affected by aci

The rain is at a distance from the areas that are really causing the problem.

Secondly, countries with large reserves of coal (such as China, India, Russia and the United States etc.) are keen to use coal as the main energy resource.

Third, the owners of thermal power plants and industries are of the opinion that the cost of adding equipment to reduce air pollution, using low-sulphur coal, or removing sulfur from coal is too high which in turn increases the cost of electricity. Will increase consumer.

The best solutions are preventive approaches to reduce or eliminate emissions of SO2, NOx and particulates

  1. Reduce the use of coal and other fossil fuels: Reducing the use of coal and other fossil fuels is the most effective way to reduce sulfur and nitrogen dioxide released into the air.
  2. Reduce air pollution by improving energy efficiency: Using energy efficient sources of energy can reduce air pollutants in the air, thereby reducing the gases that cause acid rain.
  3. The use of natural gas will have to be increased: The use of natural gas for power generation will have to be increased as an alternative to coal in thermal power plants, the main consumers of coal.
  4. Renewable energy sources should be given priority: Use renewable energy



Resources like solar energy, wind energy etc. can reduce the pollution load in the atmosphere.

  1. Burn low sulfur coal: Most of the sulfur dioxide produced, which leads to acid rain, is due to the burning of sulfur-rich coal. Before burning the coal, it can be washed. On the other hand, low sulfur coal can be replaced with high sulfur coal.
  2. Remove SO2, NOx and particulates from stack flue gases: Such equipment

scrubbers that can be installed in tall stacks or chimneys

furnaces to prevent SO2, NOx from entering the air.

  1. Remove NOX from exhaust gases of vehicles etc.
  2. The effects of acid rain can be reduced by using large quantities of limestone and lime to neutralize acidic lakes or soils.




Acid rain is a result of natural processes that occur due to chemical reactions taking place in the atmosphere. Anthropogenic activities have changed the concentrations of NOx and SO2 in the atmosphere, leading to an increase in global environmental problems.

The damage of acid rain is widespread and is known to cause extensive environmental damage to the aquatic environment, flora and fauna, human health, and buildings, structures made of stone and metal.

The best way to reduce the formation of acid rain is to reduce the emissions of SO2 and NO and this can only be done by burning less fossil fuels and adopting cleaner energy alternatives.






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