How did the smog come from?

Haze is a combination of fog and haze. Smog is very common in cities. In many areas of China, fog and haze are combined as disastrous weather phenomena for early warning and forecasting, which are collectively called "haze weather".

Haze is the result of interaction between specific climatic conditions and human activities. The economic and social activities of high-density population will inevitably emit a large number of fine particles (PM 2.5). Once the emission exceeds the atmospheric circulation capacity and carrying capacity, the concentration of fine particles will continue to accumulate. At this time, if it is affected by calm weather, it is easy to have a wide range of smog.

main sourc

human factor

Sources of toxic particles in cities:

First: it's automobile exhaust. Large vehicles that use diesel are "recidivists" who emit PM 10, including buses, shuttle buses of various units and large transport trucks. Sources of toxic particulate matter in cities: firstly, automobile exhaust. Cars that use diesel are "habitual criminals" who emit particles. Small cars that use gasoline emit gaseous pollutants, such as nitrogen oxides, which are easily converted into secondary particulate pollutants in foggy days, aggravating smog.

Vehicle exhaust is the main component of smog particles. According to the latest data, motor vehicle exhaust accounts for 22.2%, coal combustion accounts for 16.7%, dust accounts for 16.3%, and industry accounts for 15.7%. However, with the development of automobile technology and the improvement of oil quality, environmental managers have found that motor vehicle exhaust does not play a decisive role in the formation of haze weather. However, as some cities with large car ownership, managers still need to control vehicle emission standards to avoid the formation of haze weather.

Second: the waste gas produced by burning coal for heating in winter in the north.

Third: the waste gas emitted by industrial production. For example, metallurgy, kilns and boilers, electromechanical manufacturing, automobile repair and paint and building materials production produce a lot of waste gas from kiln combustion.

Fourth: Dust generated by construction sites and road traffic.

Fifth, particles can grow. The particle size of bacteria and viruses is equivalent to PM 0. 1 ~ PM 2.5. When the humidity and temperature in the air are appropriate, microorganisms will attach to particles, especially oil fume particles. After absorbing oil droplets, microorganisms will be transformed into more microorganisms, which will increase the number of biological toxic substances in smog.

6. Dust "smog" will also be produced in home decoration. Indoor dust is pervasive, which is not only harmful to the health of staff and users, but also increases the cleaning burden. When the dust is serious, it also brings many hidden dangers to the decoration project.

In addition to meteorological conditions, the increase of atmospheric particulate matter (including coarse particulate matter PM 10 and fine particulate matter PM2.5) caused by industrial production, vehicle exhaust emissions and coal burning in winter is an important factor of smog. At present, the level of pollutant discharge in many cities is at a critical point, which is very sensitive to meteorological conditions. When the diffusion conditions are good, the air quality can reach the standard, and once adverse weather conditions are encountered, the air quality and visibility will drop immediately.

climatic factor

"There is a difference between fog and haze. Fog refers to the weather phenomenon that the visibility is lower than 1 km due to the condensation of suspended water vapor in the atmosphere; The formation of smog is mainly the result of a large number of suspended particles in the air and meteorological conditions. There are three reasons:

First, the phenomenon of static wind in the horizontal direction has increased.

The higher the buildings are built in the city, the obstruction and friction of airflow passing through the urban area will be obviously weakened. The increase of static wind phenomenon is not conducive to the diffusion and dilution of suspended particles in the atmosphere, and it is easy to accumulate around urban areas and suburbs.

Second, the vertical direction is reversed.

The inversion layer is like a pot cover over a city. This inversion phenomenon that the upper air temperature is higher than the lower air temperature limits the vertical movement of the lower air, making it difficult for suspended particles in the air to drift to the upper air and be blocked at the lower air and near the ground.

Third, the increase of suspended particulate matter and organic pollutants in the air. With the growth of urban population and industrial development, the number of motor vehicles has surged, resulting in a large increase in pollutant emissions and suspended solids.