What is smog? What is the foggy weather like?

Haze is a combination of fog and haze, which is very common in cities. It is the result of interaction between specific climatic conditions and human activities. Fog is an aerosol system consisting of a large number of tiny water droplets or ice crystals suspended in the air near the ground. Haze refers to the turbidity phenomenon caused by the suspension of a large number of particles such as smoke and dust of unknown reasons.

Haze is mainly composed of sulfur dioxide, nitrogen oxides and inhalable particles. The first two are gaseous pollutants, and the last particulate matter is the main reason for aggravating smog weather pollution. Together with the fog, they make the sky gloomy in an instant. The abbreviation of particulate matter is PM, and Beijing monitors fine particulate matter, that is, pollutant particles with aerodynamic equivalent diameter less than or equal to 2.5 microns. This particle itself is not only a pollutant, but also a carrier of toxic substances such as heavy metals and polycyclic aromatic hydrocarbons.

The distribution of haze particles is relatively uniform, and the size of haze particles is relatively small, ranging from 0.00 1 micron to 10 micron, with an average diameter of about 1 ~ 2 micron. Floating particles are invisible to the naked eye. Because the smog is composed of dust and other particles, the longer the scattering wavelength, the more the light ratio, so the smog looks yellow or orange-gray.

There are many sources of smog, such as automobile exhaust, industrial emissions, building dust, garbage incineration and so on. With the deterioration of air quality, cloudy weather has increased, which has aggravated the harm and seriously affected residents' travel. In many areas, the phenomenon of haze weather is combined with fog as a warning and forecast of disastrous weather, which is collectively called "haze weather". In foggy weather, try to wear a mask when going out, and pay attention to the speed when driving.