What does PM2.5 mean and how is it formed?

PM2.5 means that the aerodynamic equivalent diameter in ambient air is less than or equal to 2.5? Micron particles. It can be suspended in the air for a long time, and the higher its concentration in the air, the more serious the air pollution.

PM2.5 generation source:

1, natural source

Natural sources include soil dust (containing oxide minerals and other components), sea salt (the second largest source of particulate matter, whose components are similar to seawater), plant pollen, spores, bacteria and so on. Natural disasters, such as volcanic eruptions, release a lot of volcanic ash into the atmosphere, and forest fires or naked coal fires and sandstorms will transport a lot of fine particles into the atmosphere.

2. Human resources

Man-made sources include fixed sources and mobile sources. Stationary sources include various fuel combustion sources, such as power generation, metallurgy, petroleum, chemistry, textile printing and dyeing, heating, cooking, coal and gas or lampblack. The flow source is mainly the tail gas discharged into the atmosphere when various vehicles use fuel in operation.

Extended data:

Compared with atmospheric coarse particles, fine particles are small in particle size, rich in a large number of toxic and harmful substances, stay in the atmosphere for a long time and have a long transportation distance, which has a great impact on human health and atmospheric environmental quality. Research shows that the smaller the particles, the greater the harm to human health. Fine particles can float far away, so the influence range is large.

Fine particles are more harmful to human health, because the smaller the diameter, the deeper the part that enters the respiratory tract. Particles with a diameter of 10μm are usually deposited in the upper respiratory tract, and those below 2μm can penetrate bronchioles and alveoli. After fine particles enter the alveoli, they directly affect the ventilation function of the lungs, making the body vulnerable to hypoxia.

Global Environment Outlook 5 released by the United Nations Environment Programme in 20 12 pointed out that 700,000 people died of respiratory diseases caused by ozone every year, and nearly 2 million premature deaths were related to particulate pollution. The Proceedings of the National Academy of Sciences (PNAS) also published a research report, which said that the average life expectancy of human beings is likely to be shortened by five and a half years because of air pollution.

References:

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