For example, according to its chemical characteristics, air pollution can be divided into two types, what are the main pollutants of each type and what are the weather conditions?

① Reduced type (coal type): The main pollutants are SO2, CO and particulate matter. Under the conditions of low temperature, high humidity, cloudy day, small wind and inversion, the pollutants are blocked over the city under the influence of local topographic conditions, causing great harm to human health and causing thousands of deaths. There have been many similar incidents, the most typical of which was the SO2 smog poisoning incident in London, the capital of England, in December 1952.

② oxidation type (automobile exhaust type): pollutants mainly come from automobile exhaust, oil-fired boilers and petrochemical production. The primary pollutants are mainly NOx and HC, and the secondary pollutants are O3, aldehydes, ketones and peroxyacetyl nitrate. It occurs in tropical and subtropical areas with strong light (subtropical high control area), and at noon or afternoon in August-September when the sun is strong. The most typical is the photochemical smog in Los Angeles around 1965.