Which of the following is a criteria pollutant and a greenhouse gas but is not directly emitted in the ambient atmosphere?

Correct option is C

Explanation:
Ozone (O₃) is a unique greenhouse gas and a criteria pollutant that is not directly emitted into the atmosphere. Instead, it forms through a photochemical reaction involving volatile organic compounds (VOCs), nitrogen oxides (NOx), and sunlight. This process typically occurs in the lower atmosphere (troposphere) and contributes to smog formation.
Key points about ozone:
1. Tropospheric Ozone is harmful to human health and vegetation.
2. Formation Mechanism: It is produced via secondary reactions, not direct emissions.
3. Criteria Pollutant: Recognized by the EPA (Environmental Protection Agency) as one of the six primary pollutants.
4. Greenhouse Gas: Contributes to warming by trapping heat in the atmosphere.
5. Stratospheric Ozone: Exists naturally in the upper atmosphere, forming the ozone layer that protects Earth from harmful UV radiation.
Information Booster:
1. Carbon Dioxide (CO₂):
· Directly emitted by burning fossil fuels, deforestation, and other processes.
· Major greenhouse gas but not classified as a criteria pollutant by the EPA.
2. Nitrous Oxide (N₂O):
· Produced from agricultural activities, fossil fuel combustion, and industrial processes.
· A potent greenhouse gas but not a criteria pollutant.
3. Nitrogen Dioxide (NO₂):
· Directly emitted during combustion in vehicles, power plants, and industrial processes.
· A criteria pollutant but not considered a greenhouse gas.
Additional Knowledge:
· Criteria Pollutants are regulated under the Clean Air Act and include:
1. Ozone (O₃)
2. Particulate Matter (PM10, PM2.5)
3. Carbon Monoxide (CO)
4. Nitrogen Dioxide (NO₂)
5. Sulfur Dioxide (SO₂)
6. Lead (Pb)
· Greenhouse Gases (GHGs) that contribute to climate change include:
1. Carbon Dioxide (CO₂)
2. Methane (CH₄)
3. Nitrous Oxide (N₂O)
4. Ozone (O₃)
5. Fluorinated Gases (HFCs, PFCs, SF₆)