AQI*** is divided into six levels, from first-class excellent, second-class good, third-class light pollution and fourth-class moderate pollution to fifth-class heavy pollution and sixth-class heavy pollution. The air pollution index is divided into 0-50,51-100,1-150,151-200,20/kloc.
This is because the AQI reaches more than 300, it is not distinguished, and it is strict! Heavy! Dirty! Dye!
When the pollutant concentration exceeds the upper limit, the highest value of AQI can only be 500, because there is no index on it. In this case, it is called "beyond the chart" or "beyond the index", that is, poor air quality can no longer be described by air quality index.
ingredient
Haze is composed of particles such as dust, sulfuric acid, nitric acid and organic hydrocarbons in the air. It will also make the atmosphere turbid, blur the vision and worsen the visibility. If the horizontal visibility is less than 65,438+00,000 meters, the sight distance obstacle caused by this non-aqueous aerosol system is called haze or dust haze, and the Hong Kong Observatory calls it haze.
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 (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.
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, sulfuric acid, nitric acid and other particles, the longer the scattering wavelength, the more the light ratio, so the smog looks yellow or orange-gray.
Refer to Baidu Encyclopedia for the above content? doubt