Acid rain is any precipitate formed when gaseous anhydride substances react with and dissolve in water and oxygen in the atmosphere.
This article discusses acid rain meaning, formation and occurrence; as outlined below;
Acid Rain Meaning: 5 Ways to Define Acid Rain
Acid rain refers to precipitation (rainfall, snow), that is formed by the dissolution and assimilation of certain acidic gases by water as it condenses and falls to the earth.
The above is a basic outline the mechanism by which acid rain forms. Some gases that are involved in acid rain formation are mentioned in the alternative acid rain meaning below;
Acid rain is any hydrogen ion-rich stream of falling droplets from atmospheric condensation, that contains gaseous anhydrides like sulfuric oxide, carbon dioxide, and nitrous oxide; dissolved from the atmosphere .
Above, the term ‘hydrogen ion-rich’ is used to signify the acidity of this type of precipitation. A clearer outline of its characteristics is provided in the acid rain meaning below;
Acid rain is precipitation that has a high hydrogen ion concentration, an average pH range of about 3.5-5.0; and acidic characteristics; and which is formed by the dissolution of anhydrous gases in the atmosphere are water droplets fall toward the Earth’s surface .
Although an average pH value can be used to describe acid rain, all atmospheric precipitates with pH less than 7.0 may be placed within this category.
Below is yet another acid rain meaning that mentions some causes of acid rain;
Acid rain is a hazardous type of atmospheric precipitation, which usually has corrosive properties, and is caused by toxin and greenhouse gas emissions from mining, gas flaring, electricity generation, manufacturing, and waste management processes, among others.
The final acid rain meaning given below, further clarifies the term ‘hazardous’ used in the preceding definition, by mentioning some effects of acid rain;
Acid rain is any low-pH, hydrogen-rich, and corrosive precipitation formed by dissolution of anhydrous gases in the atmosphere, and which could lead to environmental degradation and economic losses in the form of building damage, soil leaching, ocean acidification, loss of biodiversity and productivity in the ecosystem .
Formation of Acid Rain
Acid rain formation occurs by the emission, dispersion, and reaction of anhydrous gases like sulfuric and nitrous oxides, with oxygen and water in the atmosphere. Each of the three steps involved in the formation of acid rain, is discussed briefly below;
1). Anhydride Emission (as one of the Steps in the Formation of Acid Rain)
The first step in the formation of acid rain is anhydrous gas emission.
Anhydrous gases include all gaseous substances which produce an acidic solution when they react with, and dissolve in, water.
Examples of these gases include nitrous oxide (NO2), carbon dioxide (CO2), and sulfuric oxide (SO2). In water they may react to form nitric, carbonic and sulfuric acids respectively.
Anhydrous gases that form acid rain are generally produced from human activities and facilities, including fuel combustion in power plants, gasoline cars, electric generators, mining equipment, and biorefineries.
2). Anhydride Dispersion
Anhydride dispersion is the spread of anhydrous gases in the atmosphere, so that they reach the upper sections where condensation and precipitate formation occur, and are able to react with rainwater or snow as these condense and fall toward the ground.
Wind energy plays a major role in the dispersion and dilution of anhydrous gases.
3). Dissolution and Acidification Reactions (as one of the Steps in the Formation of Acid Rain)
Chemical reactions occur at the final stage in the formation of acid rain.
The reactions which occur are namely; oxidation, dissolution and acidification. These processes enable gaseous anhydrides to be dissolved and assimilated by rainwater or snow, to form what is known as acid rain.
Below are the reactions for acid rain formation involving sulfuric oxide (SO2), nitrous oxide (NO2), and carbon dioxide (CO2) respectively;
-Sulfuric oxide acid rain formation reactions;
2SO2 + O2 > 2SO3 —-(1)
2SO3 + H2O > H2SO4 —-(2)
-Nitrous oxide acid rain formation reactions;
2NO + O2 > 2NO2 —-(3)
2NO2 + H2O > HNO3 + HNO2 —-(4)
-Carbon dioxide acid rain formation reactions;
CO2 + H 2O ⇌ H 2CO 3 —-(5]
Where Acid Rain Occurs
Acid rain occurs in all parts of the world where significant amounts of gaseous anhydride are found in the atmosphere; including semi-urban and urban areas with high levels of large-scale industrialization. Europe, North America and Asia are among the continents where acid rain occurs most; although notable cases occur in Australia and parts of Africa as well.
Places where acid rain occurs have one or more of these characteristics;
1). High industrialization rates
2). High population density
3). Significant presence of mines, oil rigs, power plants, or other energy-related facilities
4). Large deposits of carbonate rocks
Acid rain is any precipitate that forms when anhydrous gases like CO2, NO2 and SO2 react with water and oxygen in the atmosphere.
The formation of acid rain involves three steps, which are;
1. Anhydride Emission
2. Anhydride Dispersion
3. Dissolution and Acidification Reactions
Acid rain occurs in locations characterized by industrial activities or natural resources that are rich in anhydrous gas components.
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3). Singh, A.; Agrawal, M. (2008). “Acid rain and its ecological consequences.” Journal of Environmental Biology 29(1):15-24. Available at: https://www.researchgate.net/publication/23295957_Acid_rain_and_its_ecological_consequences. (Accessed 7 November 2022).