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I want to know why the air is particularly bad today?

I want to know why the air is particularly bad today?

Air purifier 2019,Air purifier desktop,wifi air purifier

Why is the concentration of PM2.5 today so much higher than usual? Why does the morning look foggy, and at noon the air is getting better? Why is there a continuous smog in the winter, but the summer is clear? Want to know which factors affect the concentration of PM2.5, you may find the answer from this article.

The main source of PM2.5 comes from human production and life. From the current pollution source results released by the provinces, coal, motor vehicle exhaust, industrial pollution, and dust are the main sources of PM2.5. In addition, other emissions such as straw and garbage burning, food fume, livestock and poultry farming, architectural coating and sea salt particles also contribute to PM2.5. In addition to pollution sources, meteorological and topographic conditions will also have an important impact on urban air quality.

Pollution source discharge

PM2.5 emissions are divided into primary and secondary sources. Primary pollution sources are mainly PM2.5 particles directly produced by fossil fuels (oil, coal, etc.), biomass fuels (straws, wood), and dust. The secondary pollution sources are mainly PM2.5 particles produced by fossils, volatile organic compounds (VOCs) produced by biomass fuel combustion, nitrogen oxides, sulfur dioxide, hydrocarbons, nitrates, etc., which are combined with particles in the atmosphere through chemical reactions. .

For a certain area, the distribution of its pollution sources is generally fixed, and the pollutant discharge is relatively fixed, and there will be no obvious changes in a short period of time. However, with the change of seasons and changes in human production and life, the contribution of some pollution sources to PM2.5 will also fluctuate to varying degrees.

1.Heating coal during heating period

In winter, the concentration of local pollutants is high and the intensity is high. Especially in the northern regions, the temperature is low. Coal heating is used, coal consumption is significantly increased, and soot dust, nitrogen oxides and sulfur oxides are emitted in the inversion layer. It accumulates under the weather and forms a large amount of particulate matter through atmospheric reactions. This is also one of the important reasons for the high PM2.5 concentration in winter.

2.Increased vehicle exhaust emissions

Compared with summer, due to the lower temperature in winter, the gas pressure and temperature of the working cycle of the automobile engine are not high, the burning speed of the mixed gas is slowed down, or the low-speed operation of the traffic jam engine is encountered, the fuel combustion is insufficient, and the exhaust emissions of the vehicle are increased. As a result, emissions of PM2.5 and its precursors (sulfur dioxide, nitrogen oxides, VOCs, etc.) increase. The peak of daily commute is also the period of highest PM2.5 concentration in one day.


There is also a “contribution” of sandstorms in the PM2.5 concentration in the north. Although the main component of the sandstorm is PM10 particulate matter, it also contains a part of PM2.5. At the same time, strong wind blows a large amount of dust and dust on the ground and is caught in the air, combined with sulfur dioxide, nitrogen oxides and other gases in the air. Accelerate the formation of secondary particulate matter PM2.5.

4.Straw burning

North China, Northeast Spring and Autumn, southwest, and the middle and lower reaches of the Yangtze River in summer and autumn are the harvesting period of crops. At this time, burning straw has become the biggest threat to air quality pollution. When the straw is incinerated, the atmospheric sulfur dioxide, nitrogen dioxide and PM2.5 index will reach a high peak, in which the concentration of sulfur dioxide is twice as high as usual, and the concentration of nitrogen dioxide and PM2.5 is three times higher than usual. These harmful particles are extremely easy to sink, and the local ground has a large humidity, and the water vapor is sufficient, and sinking to the ground forms a haze.

Straw burning is not the main source of air pollution. From the national level, it produces less than 5% of PM2.5. However, since the straw is concentrated and burned in one or two days, on the day when the pollution is the heaviest, the PM2.5 produced by straw burning may account for 30% and 40% of the PM2.5 in the air.

5.Food fume

Although food fume is not the main source of PM2.5, it certainly contributes to PM2.5, but the proportion is relatively small. Chinese people are used to cooking, frying, frying, roasting, etc., and it is easy to make a large number of soot aerosols. Even in many parts of China, the tradition of using coal and firewood to cook rice is still maintained. The resulting pollution emissions are indeed factors that cannot be underestimated in air pollution.

The impact of food fume on air pollution is more obvious in summer. According to statistics from the Beijing Municipal Environmental Protection Bureau, cooking sources accounted for 15% to 20% of PM2.5 pollution sources in Beijing’s urban areas during the summer. Eating barbecue seems to have become part of the summer night life of the citizens. However, due to the lack of standardized management and exhaust equipment, the open-air barbecue is mostly charcoal. When cooking, it will release a lot of carbon monoxide, carbon dioxide and oil mist, and in the air. The dust combines to form PM2.5 particles.

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