Chemistry of the Atmosphere

Chapter 1: Introduction to the Chemistry of the Atmosphere

• Overview of topics: layers of the atmosphere, air pressure, air pollution, and pollution control.

• Major gases in the atmosphere:

  • Comprises 99.999% of gases like nitrogen (79%), oxygen (21%), argon, carbon dioxide, and trace gases (neon, helium, krypton, sulfur dioxide, methane, hydrogen).

Layers of the Atmosphere

• Homosphere: Chemically uniform layer up to 100-120 km above Earth.

• Heterosphere: Located above the homosphere; composition varies with altitude.

• Layers subdivided into:

  • Troposphere:

    • Closest to Earth’s surface.

    • Contains nitrogen, oxygen, and carbon dioxide.

  • Stratosphere:

    • Home to the ozone layer that absorbs UV radiation.

    • Temperature increases with height.

  • Mesosphere:

    • Temperature decreases with height.

  • Thermosphere:

    • Temperature increases with height, characterized by fewer particles.

Air Pressure

• Density of atmospheric molecules decreases with altitude.

• 50% of atmospheric mass is within the first 18,000 feet above sea level.

• Air pressure is temperature-dependent and measured in various units:

  • Atmospheres, psi (pounds per square inch), inches of mercury, pascals.

• Combined Gas Law: Describes relationship between pressure, volume, and temperature of gas.

Air Pollution

• Defined as the presence of substances in air at harmful concentrations.

• Sources of air pollution include:

  • Industrial emissions (SO₂, CO₂, NOx from combustion).

  • Natural sources (volcanic eruptions, forest fires).

• Historical examples of pollution events and their impacts on health and the environment.

Chapter 2: Sources of Pollution

• Pollution is characterized by the presence of harmful substances like dust, smoke, and gases.

• Major environmental factors contributing to pollution:

  • Meteorological Conditions: Affect movement and concentration of pollutants.

  • Sources of Pollution:

    • Natural Sources: Volcanic eruptions, forest fires.

    • Anthropogenic Sources: Industrial activities (automobile emissions, waste treatment).

Chapter 3: Types of Pollutants

• Particulate Pollutants:

  • Includes dust, mist, fly ash, smoke, and soot.

• Gaseous Pollutants:

  • Includes SO₂, NOx, CO, and volatile organic compounds.

• Effects of pollutants:

  • Harmful health effects (respiratory issues, cancer).

  • Environmental damage (acid rain, toxic effects on flora and fauna).

Chapter 4: Sampling Air

• Techniques for air sampling include:

  • Sedimentation: Collecting particles through settling.

  • Impaction: Collecting particles by impacting on a surface.

  • Filtration: Using filters to capture microorganisms and particulate matter.

Chapter 5: Control of Air Pollution

• Control techniques include:

  • Settling Chambers: Utilize gravity to remove large particles.

  • Cyclones: Remove larger particulates via inertial separation.

  • Electrostatic Precipitators: Use electrical forces to remove fine particles.

  • Fabric Filters: Capture particulates from gas streams with high efficiency.

  • Scrubbers: Effective for gaseous pollutants; can produce wastewater as a byproduct.

Chapter 6: Conclusion

• Methods for controlling gaseous pollutants:

  • Absorption: Taking in gas into liquids (commonly water).

  • Adsorption: Contaminants adhere to the surfaces of solid materials (e.g., activated carbon).

  • Condensation: Converting gas to a liquid by cooling or pressurization.

  • Incineration: Combustion of pollutants to reduce emissions.

• Regulatory frameworks, such as RA 8747 in the Philippines, promote air quality management and pollution control.