Xian air quality map

What information can be gleaned from the air quality map for Xian?

The air pollution map for Xian is very easy to access from the main city page. The map icon appears at the top of this main page and clicking anywhere on the map will open a new page with all information about current air quality.

At first glance, the map will appear to be a solid colour which represents the overall quality of air at that time. In September 2022, the map was a greenish/yellow which would indicate “Moderate” air quality. The significance of the colours used is explained in the legend at the foot of the page.

The next thing to notice is the amount of coloured discs which appear to be randomly dotted across the map. These discs show the location of the ground-level air monitoring stations in and around the city. They all contain a number which is the US AQI reading from that particular station. It is calculated by measuring the levels of six of the most prolific pollutants found in the city air. The 6 most common pollutants include particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide. The system can then be used when comparing air quality in different cities all over the world. It is endorsed by the World Health Organisation (WHO). By looking back at the main city page, it is seen that in September 2022 Xian was experiencing a period of “Moderate” air quality with a US AQI reading of 63. All six of the main pollutants were measured but it is PM2.5 that is generally used as a benchmark and its figure is quoted. The level was 18 µg/m³ which is over three times the suggested target figure of 5 µg/m³ as recommended by the WHO.

Directly beneath the air pollution map for Xian can be seen the number of active stations which provide all the data regarding air quality. Currently, there are fifteen stations providing this data.

Is there much more information about air quality on the air pollution map for Xian?

When the air pollution map for Xian is viewed in full-screen mode, a drop-down list of four options appears on the left-hand side of the screen. These options can be turned on or off as desired to make it easier to study one by one.

The first option reveals the location of all the ground-level air monitors in and around the city. As already stated, they appear as the coloured discs that contain a number. Sometimes more discs will be shown on the map that are outside the city limits but appear nonetheless. By choosing one of the individual discs, a new page will open with details about that specific part of the city.

The second option reveals the position of any wildfires that might be burning in the vicinity. There are currently two fires close to each other in the Caotang area of the city. This area is southwest of the city and the wind is blowing the ensuing smoke in the other direction, away from the city. This is known by looking at option four which shows the wind speed and direction.

The most remarkable option is number three which can change the overall colour of the map to reflect the current air quality. If some viewers find this to be too much, then by turning it off, the map reverts to a more acceptable colour palette.

Looking over to the far side of the screen will be seen a table which ranks world cities according to their level of air pollution. Some cities that may appear here could come as a surprise because they are not generally regarded as being a dirty city.

Continuing down the page, the next section reveals the areas of the city that are the most polluted. They do this by displaying a table showing the most polluted stations in descending order. Currently, the station at Caotan sits at the top of the table with a US AQI reading of 84 which is classified as being “Moderate”.

The next table shows all the stations ranked by their popularity and reveals the number of followers they each have. The most popular is the station at Xi'an-High-tech West District with almost 77,000 followers.

Is the source of the polluted air shown on the air pollution map for Xian?

The source of the polluted air is not clearly shown on the air quality map for Xian, however, in autumn and winter, the pollution emissions from heating coal combustion, biomass combustion activities and scattered coal combustion increase. In addition, the secondary transformation of nitrogen oxides emitted from industrial production and vehicle exhaust has an important "contribution" to the increase in PM2.5 concentration.

At present, the pollution in the Guanzhong area is still concentrated on coking and coal chemical industry, and the most important thing to control is to solve the problems of industrial layout and energy structure. At the same time, joint prevention and control are necessary, and the governance of diesel vehicles and low-speed trucks must be strengthened. In view of the common problems in the region, such as motor vehicles, coal burning and other prominent problems, all cities in Guanzhong should form common policies and implement them together. At the same time, it is necessary to combine long-term and short-term measures, and all departments must coordinate with each other and work together.

PM2.5 is used as a benchmark on the air pollution map for Xian, but how important is it?

PM2.5 has been listed as a first-level carcinogen by the World Health Organization (WHO), which is confirmed to be a risk factor for lung cancer. At the same time, because PM2.5 is a foreign substance, it also contains heavy metals, sulphides, and nitrides. Carcinogenic "benzene ring compounds" and other substances can cause chronic inflammation in the body, leading to hardening of the arteries and the formation of blood clots.

PM2.5 refers to "aerosol particles with a diameter of less than 2.5 microns". This size is about 1/28 of the diameter of a hair. It is very fine and can penetrate the air bubbles in the lungs and directly enter the blood vessels.

PM2.5 is inhaled through the respiratory tract, so the first level of harm to the body is the respiratory tract. Including the nose, throat, trachea, bronchioles and lungs, will cause a great impact. Because the respiratory tract is also the first level of the immune system, too much PM2.5 will stimulate immune cells such as macrophages to increase and phagocytose these particles, causing the body's immune function to lose its balance and induce cancer.