Air pollutants are divided into primary pollutants and secondary pollutants. After being discharged into the atmosphere from the pollution source, direct air pollution is called primary pollutants, mainly including sulfur dioxide, carbon monoxide, nitrogen oxides, nitrogen dioxide, particulate matter (floating dust, falling dust, oil fume, etc.), nitrogen, oxygen-containing, nitrogen, chlorine, sulfur organic compounds and radioactive substances. Secondary pollutants are pollutants exposed to sunlight, The primary pollutants discharged into the environment change under the action of physical, chemical or biological factors, or react with other substances in the environment to form new pollutants with different physical and chemical properties from the primary pollutants.
According to the above definition, which of the followings does not mention secondary pollutants:
Sulfur dioxide emitted by volcanic eruptions combined with oxygen in the atmosphere will form sulfuric acid fog or sulfate aerosol, causing environmental acidification, which will also affect climate change through direct or indirect radiation forcing