A large number of fossil fuels such as coal and oil used by humans will produce many kinds of air pollutants during the combustion process. Combustion is considered to be the first source of air pollution. These air pollutants have harmful effects on human health and the environment. Air pollutants can be divided into primary pollutants and secondary pollutants according to their sources. Pollutants discharged directly from pollution sources can be called primary pollutants, such as sulfur dioxide (SO2), nitrogen oxides (NOX) and hydrogen sulfide (H2S). Under certain conditions, the pollutants produced by the primary air pollutants participating in chemical reactions are called secondary pollutants, such as ozone (O3), peroxyacetyl nitrate (PAN) and sulfuric acid mist (H2SO4), etc. Secondary pollutants are more harmful to humans than primary pollutants.
Atmospheric pollutants can be divided into molecular state pollutants and particle state pollutants according to their presence in the atmosphere. Common molecular state pollutants such as SO2, NOX, CO, O3, etc. have low boiling points and are dispersed in the atmosphere in the form of gas molecules at normal temperature and pressure. Particle state pollutants (or particulate matter) are tiny liquid and solid particles dispersed in the atmosphere, with a particle size of 0.01-100μm, which is a complex non-uniform system. Particles smaller than 100μm are expressed as total suspended particulate matter (TSP). Particles smaller than 10μm can float in the atmosphere for a long time and are often expressed as particulate matter (PM10) or inhalable particulate matter (IP). Because of its small particle size and colloidal nature, fly dust is also called aerosol. It can be directly inhaled by the human body to cause harm in the respiratory tract, so it is one of the most eye-catching research objects. The air pollution produced by the burning of fossil energy is mainly manifested in two types: coal-based pollution and photochemical smog pollution, and the forms of harm to human health are also different. There is also marine pollution. In May 2004, the UNESCO Paris Conference reported that 48% of the CO2 emitted by humans using coal and oil is absorbed by the ocean. This means that since the beginning of the industrial revolution in the 19th century, more than 118 billion tons of CO2 have been accumulated in sea water, which has increased the acidity of sea water, thus threatening the survival of many marine organisms.
The United Nations Environment Programme warns that the “dead zones” in the earth’s oceans are increasing. In the past 10 years, the ocean dead zone has expanded significantly.