3.2 Environment - Atmospheric Chemistry (Learning Guide)

Module Overview

  • Course: Chemistry of the Environment

  • Faculty: University of Santo Tomas, Manila, Philippines

  • Subject: Atmospheric Chemistry

Intended Learning Outcomes (ILOs)

  • Explain the composition of the atmosphere.

  • Discuss major air pollutants and their sources.

  • Discuss greenhouse gases and the greenhouse effect.

Importance of Atmospheric Chemistry for Engineers

  • Air Pollution Control: Engineers must understand chemical reactions for designing pollution reduction systems.

  • Climate Change Mitigation: Engineers contribute to technology development to address climate change by studying the greenhouse effect.

  • Material Science and Corrosion: Engineers should consider atmospheric conditions' effects on material durability in product design.

  • Environmental Impact Assessment: Assessing project impacts requires understanding emissions effects on air quality and climate.

Composition of Earth’s Atmosphere

  • By Volume:

    • Nitrogen: 78.08%

    • Oxygen: 20.95%

    • Argon: 0.93%

    • Trace gases: Approx. 0.04% including greenhouse gases like CO2, CH4, N2O, and O3.

    • Water Vapor: Concentration varies with temperature.

Detailed Composition of Earth's Atmosphere

Major Gases

  • Nitrogen (N2): 78.084%

  • Oxygen (O2): 20.946%

  • Argon (Ar): 0.934%

  • Carbon Dioxide (CO2): 0.042%

  • Other Trace Gases:

    • Methane (CH4): 1.92 ppm

    • Nitrous Oxide (N2O): 0.33 ppm

    • Ozone (O3): 0.07 ppm

Layers of the Atmosphere

  1. Troposphere

    • Closest to Earth's surface, where weather occurs.

    • Contains most of the atmosphere's mass.

    • Temperature decreases with altitude.

  2. Stratosphere

    • Contains the ozone layer, which absorbs UV radiation.

    • Temperature increases with altitude due to ozone.

  3. Mesosphere

    • Temperature decreases with altitude.

    • Meteors burn up in this layer.

  4. Thermosphere

    • Temperature increases with altitude, hosting the ISS.

    • Locations of auroras.

  5. Exosphere

    • Outermost layer, gradually merging into space.

    • Satellites orbit here.

Air Pollution

Types of Air Pollutants

  • Gaseous Pollutants:

    • Sulfur Dioxide (SO2)

    • Nitrogen Oxides (NOx)

    • Carbon Monoxide (CO)

    • Ozone (O3)

    • Volatile Organic Compounds (VOCs)

  • Particulate Matter (PM): Solid or liquid particles less than 10 micrometers in diameter.

Primary vs. Secondary Pollutants

  • Primary Pollutants: Emitted directly into the air (e.g., PM, SO2, CO).

  • Secondary Pollutants: Formed from reactions between primary pollutants (e.g., tropospheric ozone).

Sources of Air Pollution

  • Natural Sources: Volcanoes, wildfires.

  • Human Activities:

    • Transportation: Cars, trucks, planes.

    • Industrial activities: Power plants, manufacturing.

Criteria Pollutants

  1. Particulate Matter (PM): Respiratory issues, categorized by size (PM10 and PM2.5).

  2. Ground-level Ozone: Formed from reactions between pollutants in sunlight, damaging lungs.

  3. Carbon Monoxide: Limits oxygen supply to the body.

  4. : Strong odor, contributes to acid rain.

  5. Nitrogen Dioxide: Irritant to respiratory system, contributes to smog.

  6. Lead: Heavy metal impacting the nervous system.

Acid Rain

  • Formed by emissions of SO2 and NOx reacting with water to create sulfuric and nitric acids.

  • Major sources include fossil fuel combustion in power generation and vehicles.

Greenhouse Effect

  • Natural greenhouse gases include CO2, CH4, N2O, and fluorinated gases.

  • Enhanced greenhouse effect enhances warming by trapping more heat.

Greenhouse Gas Sources

  • Carbon Dioxide (CO2): From natural gas systems, fossil fuel combustion, vehicles.

  • Methane (CH4): From landfills and agricultural practices.

  • Nitrous Oxide (N2O): From fossil fuel combustion and agricultural activities.

References and Resources

  • Various sources provided for further reading on atmospheric chemistry, pollution, and impacts on environment and health.