Atmospheric secondary pollutants Atmospheric pollutants are divided into primary pollutants and secondary pollutants, *** there are more than 100 kinds. From the source of pollution into the atmosphere, direct pollution of the air is called primary pollutants, mainly sulfur dioxide, carbon monoxide, nitrogen oxides, nitrogen dioxide, particulate matter (dust, dustfall, soot, etc.), ammonia, and organic compounds containing oxygen, nitrogen, chlorine, sulfur, as well as radioactive substances. Secondary pollutants is due to sunlight irradiation pollutants, pollutants between each other chemical reaction, pollutants and atmospheric components of the chemical reaction generated harmful substances, photochemical smog is a secondary pollutants. Primary pollutants interact with each other in the air or with normal components of the air to generate new pollutants generated by chemical reactions or photochemical reactions, known as secondary pollutants. Generally, their toxicity is enhanced compared to primary pollutants. A variety of primary pollutants discharged directly from the source of pollution, itself produces a chemical change, transformed into a greater toxicity than the primary pollutants of chemical substances, such as S02 into sulfuric acid fog, NO2 into nitric acid fog, as well as hydrocarbons and N02 into a photochemical smoke, etc., the latter are greater than the former toxicity. Secondary pollutants (secondarypollutant), also known as secondary pollutants, is discharged into the environment of the primary pollutants in the atmospheric environment by physical, chemical or biological factors under the action of changes or other substances in the environment to react, the transformation of the formation of a pollutant with a physical, chemical properties of different new pollutants. For example, sulfur dioxide is oxidized into sulfate aerosols in the atmosphere, and ozone and peroxyacetyl nitrate are generated by photochemical reactions of nitric oxide and hydrocarbons in automobile exhaust. The formation mechanism of secondary pollutants is often very complex, secondary pollutants are generally more toxic than primary pollutants, and their harm to organisms and human beings is more serious. Can be known by the definition