FRQ UNIT 7 Basics

What are some main pollutants?

  • PM

  • VOCs

  • NOx

  • SOx

  • COx

Sources of Main Pollutants

  1. PM (Particulate Matter):

    • Soot and smoke from burning fossil fuels (coal, oil, gas)

    • Dust from construction sites and unpaved roads

    • Combustion from vehicles

  2. VOCs (Volatile Organic Compounds):

    • Emissions from vehicle exhaust

    • Industrial processes (e.g., paint, corrosion prevention)

    • Household products (cleaners, paints, and solvents)

  3. NOx (Nitrogen Oxides):

    • Combustion processes in vehicles and power plants

    • Industrial sources

    • Natural sources (lightning, wildfires)

  4. SOx (Sulfur Oxides):

    • Combustion of fossil fuels (especially coal) in power plants

    • Refining of oil

    • Natural sources (volcanoes, oceanic sources)

  5. COx (Carbon Oxides):

    • Incomplete combustion of carbon-containing fuels (e.g., gas, coal)

    • Vehicle emissions

    • Natural sources (wildfires, volcanic activity)

Methods to Reduce Air Pollutants

  1. Electrostatic Precipitators:

    • Devices used in industrial processes to remove particulate matter (PM) from exhaust gases by using electrical charges.

  2. Catalytic Converters:

    • Installed in vehicles to reduce nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons by chemically converting them into less harmful substances before they are emitted.

  3. Scrubbers:

    • Systems that use liquid to remove pollutants from industrial gases, particularly effective for sulfur oxides (SOx).

  4. Cleaner Production Technologies:

    • Implementing processes that avoid or reduce the creation of pollutants at the source, particularly in manufacturing industries.

  5. Promoting Electric Vehicles:

    • Reducing reliance on fossil fuel-powered vehicles decreases emissions of various pollutants (NOx, COx).

  6. Improving Fuel Quality:

    • Using cleaner burning fuels, such as low-sulfur fuel, can significantly reduce SOx emissions and particulate matter.

  7. Enhancing Public Transport:

    • Encouraging public transportation usage decreases the overall number of vehicles on the road, thus reducing vehicle emissions.

  8. Tree Planting and Green Spaces:

    • Increasing vegetation can help absorb pollutants and improve air quality.

In a catalytic converter, the main inputs are harmful pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons. The catalytic converter processes these substances, and the outputs are less harmful emissions: nitrogen (N2), carbon dioxide (CO2), and water vapor (H2O). This process helps to reduce harmful pollutants from the exhaust gases of vehicles.


In the context of electrostatic precipitators, they use electrical charges to remove particulate matter (PM) from exhaust gases. The process involves applying a high voltage to create a charge on the particles, allowing them to be collected from the gas stream. This method is crucial in reducing air pollution by effectively capturing harmful particles before they are released into the atmosphere.

Scrubbers are systems used to remove pollutants from industrial gases. They work primarily by using a liquid, typically water or a chemical solution, to capture and neutralize harmful substances in the gas stream. As the gases pass through the scrubber, they come into contact with the liquid, which absorbs or reacts with the pollutants, particularly effective for sulfur oxides (SOx). The cleaned gas is then released into the atmosphere with significantly reduced pollutant levels.

Effects of Main Pollutants

  1. Particulate Matter (PM):

    • Health Effects: Can lead to respiratory issues, cardiovascular diseases, and even premature death.

    • Environmental Effects: Contributes to haze, reduces visibility, and can harm wildlife and ecosystems by settling on land and water.

  2. Sulfur Oxides (SOx):

    • Health Effects: Causes respiratory problems, aggravates asthma, and can lead to lung damage.

    • Environmental Effects: Contributes to acid rain, which can harm forests, soils, and water bodies, leading to ecological damage.

  3. Carbon Oxides (COx):

    • Health Effects: Carbon monoxide (CO) is particularly dangerous as it can cause poisoning by preventing oxygen from entering the body.

    • Environmental Effects: Carbon dioxide (CO2) is a greenhouse gas that contributes to climate change, affecting global weather patterns and ecosystems.

  4. Nitrogen Oxides (NOx):

    • Health Effects: Can lead to lung irritation, reduced lung function, and can exacerbate respiratory diseases like asthma.

    • Environmental Effects: Contributes to the formation of ground-level ozone and fine particulate matter, both of which can harm air quality and ecosystems.

Volatile Organic Compounds (VOCs):

  • Sources: Emissions from vehicle exhaust, industrial processes (e.g., paint, corrosion prevention), and household products (cleaners, paints, solvents).

  • Health Effects: Can cause respiratory problems, headaches, and other health issues due to inhalation.

  • Environmental Effects: Contributes to air pollution and the formation of ground-level ozone, which can harm ecosystems and human health.