Is sulfur trioxide a primary or secondary pollutant?

Answer 1

Coal and oli contain sulphur. When either one burns, it produces sulphur dioxide. The sulphur dioxide gradually turns into sulphur trioxide which mixes with rain and becomes acid rain. It is easy to remove the sulphur in refineries or power plants.

Answer 2

Sulfur trioxide is a secondary pollutant formed when sulfur dioxide reacts with oxygen in the presence of certain catalysts, like nitrogen dioxide or particulate matter. It is not directly emitted into the atmosphere but is produced through atmospheric reactions involving other pollutants.