Define primary and secondary pollutant?

Primary pollutants are pollutants that are directly emitted into the atmosphere from a specific source, such as vehicles, factories, or power plants. Examples of primary pollutants include carbon monoxide, sulfur dioxide, and nitrogen oxides.

Secondary pollutants are pollutants that are formed in the atmosphere through chemical reactions involving primary pollutants. These pollutants are not directly emitted into the atmosphere but are formed as a result of interactions between primary pollutants and other substances in the atmosphere. Examples of secondary pollutants include ozone, particulate matter, and acid rain.

Primary Pollutants

- Emitted directly into the atmosphere from a specific source
- Do not undergo chemical reactions in the atmosphere before reaching receptors

Examples:

- Carbon monoxide (CO)
- Nitrogen oxides (NOx)
- Sulfur dioxide (SO2)
- Particulate matter (PM)
- Volatile organic compounds (VOCs)

Secondary Pollutants

- Formed in the atmosphere through chemical reactions involving primary pollutants
- May be transported long distances before reaching receptors

Examples:

- Ozone (O3)
- Peroxyacetyl nitrate (PAN)
- Nitrate aerosols (NO3-)
- Sulfate aerosols (SO42-)
- Photochemical smog