Air pollution

Acid Rain

  • Definition: Acid rain is defined as rain water containing excessive acids, namely 60-70% sulfuric acid (H2SO4) and 30-40% nitric acid (HNO3). This forms through photochemical reactions involving nitrogen oxides (NOx) and sulfur oxides (SOx) in the atmosphere.

  • Formation Process:

    • The combustion of fuels (coal, fuelwood, petroleum) releases oxides of nitrogen and sulfur into the atmosphere.

    • These oxides undergo photochemical reactions, producing H2SO4 and HNO3, which then mix with hydrochloric acid (HCl) to precipitate as acid rain.

    • Key Reactions:

      • NO2 + light -> NO + O3

      • 2NO + light -> 2NO2

      • SO2 + 1/2 O2 -> SO3 (with catalyst)

Consequences of Acid Rain

  1. Environmental Impact:

    • Increases soil acidity, harming human and aquatic life, destroying forests and crops, thus reducing agricultural productivity.

  2. Corrosion:

    • Corrodes buildings, monuments, and infrastructure.

  3. Health Hazard:

    • Contaminates air and drinking water, potentially leading to neurological diseases.

  4. Biological Effects:

    • Leads to the decline of fish populations and disrupts aquatic ecosystems.

    • Heavy metals, such as cadmium, are more easily absorbed by plants due to acidifying conditions.

  5. Mineral Depletion:

    • Harms the mineral wealth present in soils, stripping essential nutrients.

Ozone Formation and Depletion

Formation of Ozone

  • Location: The stratosphere (15-60 km above the Earth's surface).

  • Role of Ozone:

    • Absorbs ultraviolet (UV) radiation, protecting living organisms from harmful effects.

  • Formation Process:

    • Ozone is formed through photochemical reactions involving oxygen (O2) and UV light:

      • 3O2 + UV light -> 2O3

Ozone Depletion

  • Significance: The ozone layer protects against UV radiation.

  • Ozone Hole: First identified in 1985 over Antarctica due to depletion by ozone-depleting substances (ODS) such as chlorofluorocarbons (CFCs).

  • Causes of Depletion:

    • CFCs release chlorine in the stratosphere, which catalyzes ozone destruction:

      • CFC + UV -> Cl + other products

  • Consequences:

    1. Increased UV radiation leads to higher skin cancer rates and other health issues.

    2. Damages ecosystems, including sensitive marine life.

Photochemical Smog

  • Definition: Hazy, brownish air pollution primarily caused by sunlight interacting with pollutants from vehicle exhaust.

  • Characteristics:

    • Causes irritation to eyes and respiratory organs and damages vegetation.

    • First identified as