Acid Rain


Introduction of Acid Rain:

Rain or any other type of precipitation with an extremely high concentration of hydrogen ions (low pH) refers to as acid rain. The neutral pH of most water, including drinking water, is between 6.5 and 8.5; acid rain, on the other hand, typically has a pH between 4-5. The pH of acid rain decreases with increasing acidity. Infrastructure, marine life, and plants can all suffer from acid rain’s negative impacts. Emissions of nitrogen oxide and sulphur dioxide combine with atmospheric water molecules to form acids, which is what causes acid rain.

It has been demonstrate that acid rain negatively affects freshwater ecosystems, soils, microorganisms, insects, and aquatic life forms. Persistent acid rain weakens the resilience of tree bark in ecosystems, making plants more vulnerable to environmental stresses including pest infestation, heat waves, and drought. Additionally, acid rain can harm the composition of soil by depleting it of elements like calcium and magnesium, which are essential for plant growth and the upkeep of healthy soil. Acid rain affects human health in addition to causing paint to peel, steel structures like bridges to corrode, stone buildings and sculptures to weather, and other aspects of human infrastructure.


  • Acid rain refers to any precipitation (rain, fog, mist, snow) that is more acidic than normal (pH of less than 5.6. pH below 7 is acidic).
  • Acid rain cause by atmospheric pollution from acidic gases such as sulphur dioxideand oxides of nitrogen emit from the burning of fossil fuels.
  • It’s also recognize that acidic smog, fog, mist, move out of the atmosphere and settle on dust particles which in turn accumulate on vegetation as acid depositions.
  • When rain falls, the acid from these depositions leak and form acid dew


  • A solution’s acidity or basicity (alkaline) can be determining using the pH scale.
  • The range is 0 to 14. where 7 is the neutral pH
  • An acidic pH is less than 7, and a basic pH is larger than 7.
  • Its foundation is the concentration of hydrogen ions in an aqueous solution.
  • As hydrogen ion levels rise, pH values fall.
  • A pH 4 solution has ten times the acidity of a pH 5 solution and one hundred times the acidity of a pH 6 solution.
  • Although the pH range typically state as 0 to 14, it’s theoretically feasible to have lower or higher values.

Types of Acid Rain Deposition

  • “Acid rain” is a broad term referring to a mixture of wet and dry deposition (a form of deposition material) from the atmosphere.

Wet Deposition

  • Rain, snow, fog, or mist some of the ways that the acid chemicals in the air can descend to the ground if they blown into moist weather conditions.
  • This acidic water impacts a wide range of plants and animals as it percolates through and across the earth.

Dry Deposition

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


  • Surface waters and aquatic animals- Fish and other aquatic species may suffer harm from the lower pH and increased aluminium concentrations in surface water brought on by acid rain. Most fish eggs won’t hatch at a pH of less than 5, and lower pH can even kill adult fish. The amount of biodiversity decreases as rivers and lakes becoming more acidic. However, depending on the features of the surrounding watershed, acid rain’s direct or indirect contribution to the acidity of lakes and rivers through catchment runoff varies. 
  • Soils- Acid rain can cause significant harm to the biology and chemistry of soil. Certain microorganisms die when their pH drops because they can’t survive the change. The acid denatures (modifies the form of) these microorganisms’ enzymes, rendering them inactive. In addition to mobilizing pollutants like aluminium, acid rain’s hydronium ions also steal vital nutrients and minerals like magnesium.
  • Soil Acidification- Acidic water seeps into the plant, dissolving and carrying away vital plant minerals until the plant dies from a shortage of minerals for nourishment. The loss of vital minerals happens in major cases, which are more severe, in a manner similar to that of minor cases but much more quickly. Similarly, acid rain that falls on soil and leaves dries off the waxy cuticles on leaves, which leads to a rapid loss of water from the plant to the atmosphere and ultimately to the plant’s death. It’s possible to determine whether a plant is impacts by soil acidity by thoroughly examining its leaves. If the leaves appear healthy and green, the pH of the soil is normal, which is suitable for plant growth. However, if there is yellowing between the veins on the leaves, the plant is ill and experiencing acidity.
  • Forests and other vegetation- Adverse effects may be indirectly related to acid rain, like the acid’s effects on soil (see above) or high concentration of gaseous precursors to acid rain. High altitude forests especially vulnerable as they are often surrounding by clouds and fog which more acidic than rain.
  • Ocean Acidification- Globally, acid rain is far less hazardous to oceans than it is to coastal waters, where its effects are compounded in shallower seas. Acid rain can lead to ocean acidification, a decrease in the pH of the water that makes it more difficult for some coastal animals to form the exoskeletons necessary for survival. As a component of the ocean’s food chain, these coastal species are interconnected, and more marine life will perish if they are not a source for other marine species to eat. Because calcium carbonate, a vital component of the limestone skeleton, dissolves in acidic (low pH) solutions, coral’s limestone skeleton is especially vulnerable to pH drops.
  • Human health effects- Human health is not directly impacted by acid. Rainwater has too little acid to be harmful directly. There are negative effects associated with the particulates that cause acid rain, specifically nitrogen oxides and sulphur dioxide. When these particles combine and react in the atmosphere, fine sulphate and nitrate particles are created.  High exposure to these particles, especially over an extended length of time, can lead to skin and eye irritation, increased lung fluid, and erosion and damage to teeth. Airborne fine particulate matter concentrations that are too high are linked to respiratory and cardiac issues, such as asthma and bronchitis. These specific impacts on the heart and lungs can change how they operate, and in those who are more susceptible to heart disease and other heart disorders, a heart attack can be fatal.

Sources- THE HINDU, NCERT, Wikipedia