Air-Acid Rain

Rain has a pH value between 5.0 to 5.5, which is slightly acidic because the reaction of carbon dioxide in the atmosphere with rainwater produces H+ ions.

H2O (l) + CO2 (g) ⇆ H2CO3 (aq) 

H2CO3 (aq) ⇆ H+(aq) + HCO–3 (aq)

But due to pollution caused by the burning of fossils, which releases oxides of sulphur and nitrogen in the atmosphere, it reacts with water to form(Sulphuric acid ) H2SO4 and HNO3 (Nitric acid). The polluted air usually contains particles of catalysts for oxidation.

2SO2 (g) + O2 (g) + 2H2O (l) → 2H2SO4 (aq)

4NO2 (g) + O2 (g)+ 2H2O (l) → 4HNO3 (aq)

Acid Rain

Acid rain is a phenomenon caused due to pollution occurring through burning fossil fuels like coal, petrol, and diesel, which contain sulphur and nitrogenous matter. After burning, these materials release sulphur and nitrogen oxides in the atmosphere, which further mix with rainwater, snow, and fog to form wet deposition or solid particles settling down as dry deposition. 

There are two types of depositions in which acid rain falls on the surface of the earth:

• Dry deposition 
• Wet deposition

Dry Deposition

Dry deposition happens when the sulphur and nitrogen oxides do not mix with the precipitation, and then these particles stick to the ground, vegetation or any other surface. Dry deposition contributes to 20% – 60% of total acid deposition. 

Dry deposition is expected in dry areas like desserts with little to no rainfall and low humidity.

Wet Deposition

Wet deposition occurs mainly through rain, snow or any other form of precipitation that gets contaminated through oxides of nitrogen and sulphur oxides present in the atmosphere.

Causes

Natural Causes

The major part of acid rain caused due to natural causes is because of emissions from volcanoes. For example, fumes from Poás Volcano release extreme amounts of acid rain and fog, with acidity up to pH 2. Acid rain destroys plant life near it and respiratory ailments in nearby settlements.

Humans

The primary cause of acid rain is sulphur oxides and nitrogen oxides produced by human activities. It is the burning of fossil fuels to generate electricity, factories, and motor vehicles. Industrial acid rain is a serious issue in China, Russia and other countries with a large population and big industry that depends on the burning of fossil fuels for their functioning.

Effects on the Environment

Aquatic life

When acid rain falls and deposits on the grounds, it starts seeping down through soils, reaches underground water sources, and then gets rivers and other aquatic bodies, or acid rain directly falls on large water bodies like oceans and lakes. 

It affects the marine life inside these aquatic bodies. It makes the water toxic for crayfish, clams, fish and other aquatic animals; fish eggs do not hatch if the pH is less than 5, and pH lower than that can kill adult fishes. Acid rain has led to the extinction of many species of insects and fish.

Acidification of soil

When acidic rain falls on the soil, it washes away the nutrient from the ground and which in most cases is not fatal for the plant life, but the plants eventually die due to the acidic water lowering the plant’s natural pH. When the pH of acid raindrops to a potent level and the rain falls on the leaves of the plant, it causes drying of the waxy leaf cuticle, which leads to a rapid water loss in the plant and eventually leads to the death of the plant. 

To observe the effects of soil acidification in plants, we can observe the plant’s leaves. If the leaves look green and healthy, this means the pH of the soil is at a sustainable level, but if there is yellowing in the beans of the leaves, then it means that the plant is suffering from acidification.

Effects on forest and other plant life

Often, forests at high altitudes are vulnerable to acid rain because of the cloud and fog in the surroundings, which are more acidic than the rain.

Crops can also be heavily damaged by acid rain, but to minimise this effect, line and other fertilisers are used to replenish the nutrients in the crop soil.

Acidification in oceans

Acidification of oceans happens mainly in the coastal areas. Disturbance in the growth of coastal species disturbs the whole food chain of marine life.

This acidification makes it difficult for many coastal species to form exoskeletons that they need to survive. The Exoskeletons of many species of corals are sensitive to the pH of the water since it is made out of limestone, which dissolves in acidic solutions.

Human life

Acid rain doesn’t have any direct effect on human life. Still, it increases the amount of particulate matter found in dry deposition, Resulting in many types of Respiratory disorders like asthma and bronchitis and other respiratory diseases like asthma and bronchitis.

Infrastructure

Acid rain reacts with many materials used to construct monuments and buildings. Statues, buildings and monuments made of materials like limestone marble start creating flakes of gypsum when they come into contact with acid rain; this results in disfiguration and declaration.

Infrastructure that uses heavy metals like iron and steel is often affected by acid rain because it increases its corrosion speed.

Conclusion

As we have learned that acid rain is harmful to the environment and is a serious issue that concerns everyone, it affects life on earth through different means. It happens when oxides of sulphur and nitrogen contaminate precipitation. Acid rain harms the infrastructure created by humans and humans, wildlife, vegetative life, and aquatic life around us directly or indirectly.