TOPIC 3 Air pollution

Air Pollution ECW445

Learning Outcomes

At the end of this chapter, students should be able to:

• Identify various sources of air pollution, including both natural and anthropogenic origins.

• Explain the importance of air quality assessment and describe the tools used for measuring air quality.

• Discuss the diverse impacts of air pollution on the environment, economy, and human health.

What Is Air Pollution?

Definition: Air pollution refers to the alteration of the natural components of the atmosphere due to the presence of harmful chemical substances, particulate matter, or biological agents, which can negatively affect human health and the environment.

Atmosphere Layers

Composition of the Atmosphere:

• Nitrogen (N2): comprises approximately 75% of the atmosphere,

• Ozone layer: accounts for about 24% of the atmosphere, which plays a crucial role in shielding the Earth from harmful ultraviolet (UV) radiation.

Characteristics:

• The atmosphere exhibits cold temperatures with fewer molecules in the stratospheric layers.

• Large temperature fluctuations are expected between different atmospheric layers.

• Occasionally, molecules escape into outer space, a phenomenon more common in the higher strata of the atmosphere.

Gases Composition in Unpolluted Air

Gaseous Composition (Dry Basis):

• Nitrogen (N2): 780,000 ppm (80%)

• Oxygen (O2): 209,400 ppm (20%)

• Argon (Ar): 9,300 ppm (0.93%)

• Carbon Dioxide (CO2): 315 ppm (0.038%)

• Minute traces of other gases, including noble gases and water vapor, contribute to the overall composition.

Forms of Pollutants

Types of air pollutants can be segmented into the following categories:

• Gases: such as carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), and volatile organic compounds (VOCs).

• Liquids (Aerosols): tiny liquid droplets or particles suspended in the air that can include mist, fog, and spray from industrial processes.

• Solids (Particulate Matter): includes dust, soot, and smoke particles that can be inhaled and cause respiratory issues.

Sources of Air Pollution

Natural Sources:

• Dust arising from deserts and dry land areas can be lifted into the atmosphere and contribute to air quality issues.

• Methane emissions from livestock and wetlands can add to greenhouse gas concentrations.

• Smoke produced from forest fires can introduce significant air pollutants.

• Volcanic activity releases ash and gases that can drift over vast distances.

• Sandstorms can significantly affect air quality in arid regions.

• Natural events like lightning strikes can produce nitrogen oxides (NOx).

• Biological decay processes release various gases, including methane.

• Radioactivity of certain rocks can introduce elements like radon into the air.

• Pollen produced by plants can also contribute to seasonal air quality issues.

Anthropogenic Sources:

• Stationary sources: consist of smoke stacks from power plants and manufacturing facilities that emit a variety of pollutants into the atmosphere.

• Mobile sources: include emissions from motor vehicles, aircraft, and marine vessels that operate on roads, airways, and waterways, respectively.

• Controlled and open burning in agricultural practices can lead to harmful emissions.

Additional Anthropogenic Sources:

• Crop waste burning practices release smoke and particulates into the air.

• Fumes from paints, solvents, and aerosols can emit VOCs that contribute to air pollution.

• Landfills generate methane as organic waste decomposes, impacting local air quality.

• Military activities, such as the use of nuclear weapons and toxic gases, can introduce harmful pollutants.

Classification of Air Pollutants

• Primary Pollutants: These are pollutants that are directly emitted into the atmosphere. Examples include ash, carbon monoxide (CO), and sulfur dioxide (SO2).

• Secondary Pollutants: These pollutants form in the atmosphere through chemical reactions involving primary pollutants. Ground-level ozone (O3) is a prominent example.

Major Categories of Air Pollutants

Primary Pollutants:

1. Sulfur Oxides (SOx)

2. Nitrogen Oxides (NOx)

3. Carbon Monoxide (CO)

4. Carbon Dioxide (CO2)

5. Particulate Matter (PM)

6. Volatile Organic Compounds (VOCs)

7. Toxic Metals such as lead and mercury

8. Chlorofluorocarbons (CFCs) which contribute to ozone layer depletion.

9. Ammonia (NH3), which can lead to the formation of secondary particulate matter.

10. Odor emissions, such as those from waste disposal.

11. Radioactive pollutants, including radon from natural sources.

Secondary Pollutants:

• Particulate Matter (PM): that can originate from various primary pollutants.

• Ground-level Ozone (O3) created by photochemical reactions.

• Peroxyacetyl nitrate (PAN), a complex organic compound produced in urban smog.

Concluding Notes

This note synthesizes essential details surrounding air pollution including definitions, components, classifications, sources, and effects, providing a foundational understanding of the subject matter that will facilitate the learning of air quality assessment and the impacts associated with pollution. A thorough grasp of these concepts is crucial for developing effective strategies for managing and mitigating air pollution issues.