Primary Air Pollutants: Sources, Impacts, and Control

Posted on Oct 31, 2024 in Chemistry

Primary Air Pollutants

Sulfur Dioxide (SO2)

Properties: Colorless gas, reactive, soluble, and has a pungent odor at higher concentrations.

Sources:

  • Natural: Organic matter decomposition, volcanic eruptions.
  • Anthropogenic: Industrial processes (fossil fuel combustion, refining, chemical manufacturing).

Fate: Oxidizes to form SO3, leading to acid rain through dry and wet deposition.

Nitrogen Oxides (NOx)

Properties: NO (nitric oxide) is colorless, odorless, and non-flammable. NO2 (nitrogen dioxide) is a reddish-brown gas, slightly soluble, and toxic.

Sources:

  • Natural: Volcanic eruptions, lightning.
  • Anthropogenic: Combustion processes (vehicles, power plants, industrial furnaces).

Fate: Contributes to photochemical smog and acid rain formation.

Carbon Monoxide (CO)

Properties: Colorless, odorless, slightly soluble in water, less dense than air.

Sources:

  • Natural: Organic matter decomposition, oxidation of methane.
  • Anthropogenic: Incomplete combustion of fossil fuels (vehicles, industrial processes).

Fate: Oxidized to CO2 in the atmosphere.

Particulate Matter (PM)

Sources:

  • Natural: Volcanic eruptions, forest fires, sea spray.
  • Anthropogenic: Combustion processes, industrial activities.

Formation:

  • Primary Particles: Directly emitted into the atmosphere.
  • Secondary Particles: Formed through gas-to-particle conversion.

Particle Growth:

  • Nucleation: Condensation of gases into particles.
  • Homogeneous Nucleation: Condensation without a foreign element.
  • Heterogeneous Nucleation: Condensation with a foreign element.

Atmospheric Processes: Brownian motion, turbulent coagulation.

Atmospheric Oxidation Processes

  • Homogeneous Oxidation: Photooxidation, radical reactions.
  • Heterogeneous Oxidation: Reactions on particle surfaces, aqueous-phase oxidation.

Air Quality Monitoring

Surveillance Networks: Systems of monitoring stations that measure air pollutant concentrations.

Station Types: Manual and automatic.

Objectives: Assess air quality, protect public health, support research, inform the public.