Short Answer

Acid rain is the precipitation (rain, snow, sleet, or fog) that has a higher acidity than normal, usually with a pH below 5.6. It forms when sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) react with water in the atmosphere, forming acids like sulfuric acid and nitric acid.

Acid rain can damage crops, forests, water bodies, and buildings, making it a serious environmental concern. Human activities such as burning fossil fuels are major contributors.

Detailed Explanation :

Definition of Acid Rain

Acid rain is a form of rainwater that contains dissolved acidic components, primarily sulfuric acid (H₂SO₄) and nitric acid (HNO₃). It can fall as:

• Rain
• Snow
• Sleet
• Fog or mist

Normal rain is slightly acidic (pH ≈ 5.6) due to dissolved carbon dioxide forming carbonic acid, but acid rain is more acidic (pH < 5.6).

1. Formation of Acid Rain

1. Emission of Pollutants
   • Sulfur dioxide (SO₂) and nitrogen oxides (NO, NO₂) are released from vehicles, power plants, and industrial factories.
2. Chemical Reactions in the Atmosphere
   • SO₂ reacts with oxygen and water:

1. • NOₓ reacts with water:

1. Deposition
   • The acids dissolve in rainwater and fall on land, water bodies, and structures, causing acid rain.

2. Types of Acid Rain

1. Wet Deposition
   • Acidic rain, snow, sleet, or fog that falls from the sky.
2. Dry Deposition
   • Acidic gases and particles that settle on surfaces in the absence of precipitation.

Both types contribute to soil acidification, water pollution, and material damage.

3. Causes of Acid Rain

1. Natural Sources
   • Volcanic eruptions release SO₂.
   • Lightning produces NOₓ naturally.
2. Human Activities
   • Burning fossil fuels (coal, oil, gas) in power plants, vehicles, and industries.
   • Industrial processes like metal smelting.

Human activities are the primary contributors to modern acid rain.

4. Effects of Acid Rain

1. Environmental Effects
   • Lakes and rivers: Acidic water harms fish and aquatic life.
   • Soil: Leaches nutrients and releases harmful metals.
   • Forests: Damages leaves, bark, and roots, reducing growth.
2. Material Damage
   • Corrodes buildings, monuments, and statues, especially made of limestone and marble.
3. Health Effects
   • Indirectly affects humans via contaminated water and food.
   • Causes respiratory problems due to acid-laden air pollutants.

5. Prevention and Control

1. Reducing SO₂ and NOₓ emissions
   • Use clean fuels, scrubbers, and catalytic converters.
2. Alternative Energy
   • Solar, wind, and hydroelectric power reduce fossil fuel use.
3. Liming of Soil and Water Bodies
   • Adding calcium carbonate neutralizes acidity in forests and lakes.
4. International Policies
   • Regulations like Clean Air Act and agreements between countries reduce emissions.

6. Summary

• Acid rain is caused by SO₂ and NOₓ reacting with water in the atmosphere.
• It falls as wet or dry deposition and is more acidic than normal rain.
• Major effects include environmental degradation, material corrosion, and health hazards.
• Prevention requires reducing emissions, using alternative energy, and neutralizing acidic soils and waters.

Conclusion

Acid rain is a serious environmental problem caused mainly by human activities that release sulfur and nitrogen compounds. Its acidic nature leads to damage to ecosystems, structures, and human health. Understanding its causes, effects, and control measures is crucial for sustainable development and environmental protection. Measures like reducing emissions and using cleaner energy can significantly minimize acid rain and its harmful impacts.