Which of the following is not a primary pollutant?

Explanation

Primary pollutants: Emitted directly into the atmosphere from a source without significant chemical alteration.Secondary pollutants: Formed in the atmosphere through chemical reactions between primary pollutants or other atmospheric constituents.Although H₂SO₄ (sulfuric acid) contributes to acid rain, sulfuric acid doesn't directly enter the atmosphere from a source. It forms in the atmosphere through complex reactions involving sulfur dioxide (SO₂), a primary pollutant from volcanic eruptions and fossil fuel combustion, with water vapor and hydroxyl radicals (OH). Therefore, it's a secondary pollutant.Now we'll look at why other options are incorrect.(a) SO₃ (sulfur trioxide): This can be considered a primary pollutant as it's directly released during the combustion of sulfur-containing fuels like coal.(b) CO (carbon monoxide): Another primary pollutant, directly emitted from incomplete combustion processes like in vehicles, industrial activities, and biomass burning.(c) NO (nitrogen oxide): Primarily originates from high-temperature combustion in vehicles, power plants, and industrial processes. Hence, it's a primary pollutant.(Environmental chemistry,Components of Environment)