What is smog made of?

Haze is mainly composed of sulfur dioxide, nitrogen oxides and inhalable particles, which combine with fog to make the sky dark and gloomy in an instant.

The abbreviation of particulate matter is PM, and Beijing monitors fine particulate matter (PM2.5), 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.

Fog is an aerosol system consisting of a large number of tiny water droplets or ice crystals suspended in the air near the ground. It mostly appears in autumn and winter, and it is the product of water vapor condensation (or condensation) in the air near the ground.

The existence of fog will reduce air transparency and worsen visibility. If the horizontal visibility of the target drops below 1000 meters, the weather phenomenon of water vapor condensation (or condensation) suspended in the air near the ground is called fog.

Extended data:

The formation of smog has both a "source" and an "accomplice", which is a meteorological condition that is not conducive to the spread of pollutants. Once pollutants accumulate for a long time under static meteorological conditions, it is easy to form haze weather. The formation of smoke has three elements:

The first is the physical basic source of particulate matter. China has the largest loess plateau in the world, and its soil texture is the easiest to produce granular dust particles.

Second, poor exercise leads to dust. For example, the mud in the garden in the middle of the road and the soil on the roadside stones will flow to the road after raining or splashing water, which will produce a lot of dust after one hour of drying. Even if these particles fall back to the ground, they will be thrown over the city again because of the continuous passing of cars.

Thirdly, the basic source of dust and the process of movement difference gather in a certain spatial range, and particles finally gather with water molecules to form haze. At present, in more than 350 cities in the Loess Plateau of China, the three elements of smog structure are quite rich.

Baidu encyclopedia-smog