At what height is the most polluted in the air

Why Air Testing? The reason is that indoor environmental pollution has become one of the killers that seriously affects human health.

The importance of indoor air quality We spend more than 70% of our time in the indoor environment. Good indoor air quality is the most important factor to ensure good health, substandard indoor air can lead to physical discomfort and poor health (such as headache, chest tightness, drowsiness, allergies, eye strain, frequent colds, etc.). Pregnant women, children, the elderly, office workers, and people with respiratory and cardiovascular diseases are more susceptible to poor indoor air quality.

Common Indoor Air Pollutants 1Contamination of building materials. The gypsum board used in modern building decoration breeds bacteria, viruses and other microorganisms; 2.

Pollution caused by enclosed buildings. The fully enclosed building isolates the flow of natural fresh air....

In plains, or in relatively open areas, the fog is most abundant on the ground, and in narrow cols, the fog is most in the middle of the mountain. Similarly, oxygen is abundant on the ground in a plain, in a wide area, and in a chimney-like terrain, the height of the place where the oxygen is most abundant will rise with the chimney. For example, the oxygen content at the bottom of the well is the highest oxygen content at the wellhead.

For example, in deep mountain valleys, the place where the most oxygen is generated is not at the bottom of the mountain, but on the mountainside. Normally, except for places where the chimney terrain is, the lower the altitude, the more oxygen there is.

The air quality status is highly polluted. Healthy people have reduced exercise tolerance, obvious strong symptoms, and early appearance of certain diseases, it is recommended that children, the elderly, and the sick should stay indoors to avoid physical exertion, and the general population should avoid outdoor activities.

In the new ambient air quality standard, pollutant concentration limits are converted into air quality sub-indices of up to 500. In other words, once the average daily concentration exceeds 500 microgram cubic meters, the AQI immediately reaches 500.

Improvements. 1. Establish an air quality monitoring mechanism and implement national environmental protection policies.

2. Strengthen the development of industrial energy models and continue to replace fossil energy.

3. Develop pollution-free new energy sources such as solar energy and expand human energy sources.

4. Introduce laws and regulations to strictly restrict the discharge of firecrackers during festivals and reduce the emission of harmful gases.

5. Provide collective heating to reduce heating costs.

6. Plant trees frequently, open more canals, and reduce sewage discharge.

7. Use air purifiers to prevent and control indoor air pollution.

8. Take buses and subways as much as possible when traveling, and reduce the use of private cars; Installing an exhaust gas processor or using fuel lubricants reduces vehicle exhaust emissions.

9. For factories with high pollution and energy consumption, we will carry out comprehensive transformation, and carry out harmless treatment of waste gas and waste water to achieve energy conservation and emission reduction.

The above content refers to Encyclopedia - Air Quality.

In our country, the average household has a value between 35 and 75.

According to the indicators given by the national air health standards, if the value is less than 35, it can mean that the air quality is very good, and there is no harm to the human body, but if the value is between 35 and 75, it means that the air quality is good and suitable for people's life, but in many seriously polluted areas, there will be more than 75 or even higher, which indicates that the environment has been seriously polluted.

1. The nature of pollutants: physical and chemical.

2. The nature of the pollution source: source strength, source height, source temperature, exhaust rate, etc.

3. Meteorological conditions: wind direction, wind speed, temperature stratification, etc.

4. Surface properties: terrain undulation, roughness, ground cover, etc.

There are two causes of air pollution: natural factors (such as forest fires, volcanic eruptions, etc.) and human factors (such as industrial exhaust gases, domestic coal burning, automobile exhaust gases, etc.), and the latter is the main factor, especially caused by industrial production and transportation.

The main process is composed of three links: pollution source discharge, atmospheric transmission, and human and material damage.

Governance measures. The world's main measures to reduce sulphur dioxide emissions:

1. Raw coal desulfurization technology can remove about 40% to 60% of the inorganic sulfur in coal. Priority is given to low-sulphur fuels, such as low-sulphur coal and natural gas, which contain less sulphur.

2. Improve coal-fired technology and reduce the emission of sulfur dioxide and nitrogen oxides in the process of coal burning. For example, liquefied coal-fired technology is one of the new technologies that has been welcomed by various countries. It is mainly used to add limestone and dolomite, react with sulfur dioxide, and generate calcium sulfate to be discharged with ash.

The flue gas formed in clusters after coal combustion is desulfurized before it is discharged into the atmosphere.

3. The lime method is mainly used, which can remove 85%-90% of the sulfur dioxide gas in the flue gas. However, although the desulfurization effect is good, it is very expensive. For example, the cost of installing a flue gas desulfurization unit in a thermal power plant can be as much as 25% of the total investment in the power plant.

This is also one of the main difficulties in managing acid rain.

4. Develop new energy, such as solar energy.

The air pollution index is greater than 300, the air quality level is V, and the air quality status belongs to severe pollution and rapid molding. At this time, everyone's health will be seriously affected, the elderly and the sick should stay indoors, avoid physical exertion, and the general population should minimize outdoor activities.

The Air Pollution Index** can be used to remind the public, especially those who are sensitive to air pollution, such as those suffering from heart disease or respiratory problems, to take precautions before severe air pollution conditions occur.

At about 30 meters, that is, between the 8 and 11 floors.

Pollutants near the ground rise to a certain height with the airflow and then dissipate downward or horizontally.

Under normal conditions, the air temperature decreases with the increase of altitude, and the temperature decreases about 100 degrees on average, so that the temperature in the lower layers of the atmosphere is high and the air density is small; The low temperature in the upper layer and the relatively high density of the air cause the phenomenon of "top-heavy", and the atmospheric stratification is unstable and easy to tumble up and down to form convection.

In this way, the pollutants and dust in the air in the lower layers, especially near the ground layers, will be dispersed to the upper altitude, thereby reducing the degree of pollution in the lower layers of the atmosphere. The dispersion height is the ash layer in environmental science, and the existence of the ash layer refers to: "Due to the influence of air flow and building microenvironment, part of the dust density of the building within a certain height range is larger.

In other words, the dust and harmful substances in the air have a process of staying at this height, in fact, due to the influence of the "canyon effect" (the "canyon effect" refers to the surrounding bus arteries, factories, and high-rise residential buildings, under the action of street wind, the air flow containing dust does not move smoothly, but "wanders" up and down a certain area between high-rise buildings). ）

In the case of air pollution, the distribution of pollutants is constantly changing, ranging from tens of meters to hundreds of meters, and does not stay fixed at one height, so there is no need to say how many meters are the most polluted.

Under normal circumstances, pollutants in the air continue to settle and flow with the airflow, and in the absence of pollution sources in the air, the higher the floor, the cleaner the air is. The higher the altitude of the atmosphere, the lower the temperature, and the air is prone to convection, which allows pollutants to disperse.

In autumn and winter and under special climatic conditions, the temperature will increase with the altitude, and the atmosphere will appear "inversion layer". The thickness of the inversion layer varies from tens of meters to hundreds of meters, like a thick quilt covering the city, hindering the dispersion of urban pollutants. However, the height of the inversion layer is variable, and the distribution of pollutants under inversion conditions is also constantly changing, and does not stay fixed at one height.

"The 9th and 11th floors of high-rise buildings are ash floors, and the dirty air stops at this level, where the density of pollutants is ......The story of the building building building has been widely circulated and has caused some people to worry. Does the ash layer exist? Will particulate matter in the air accumulate at a height of 9-11 layers to form a polluted area?

The reporter of the people's ** "verification" column investigated and interviewed and found that the so-called "9-11 floors are ash layers" is unscientific.

Layer 9-11 is the most polluted?

Response] PM10 concentration on each floor is not much different.

In the sales department of a real estate near the forest park in Yinchuan City, Ningxia, salesman Liu Lijuan said that she had heard the saying that "the 9-11 floors are the ash layer", and some customers asked when buying a house, but they felt that it had no impact on sales.

In a new project outside the third ring road in Chengdu, Sichuan, Yang Xiaogang took his family to pick a house, and when asked if he would choose the 9th-11th floor, he refused: "I won't choose." It is said that those layers are the most polluted layer of raised ash. ”

Han Shitong, a real estate expert in Guangzhou, said that the statement that "the 9-11 floors of the building is the ash layer" originated from a 2003 "Confessions of the Sales Lady" online article, which said in a "revealed" tone: "Don't think that the 9-11 floors in the high-rise are good, these floors are just ash layers, and the dirty air will stop at this height." The opinion in the article has not been scientifically confirmed, but the claim has spread and it is difficult to distinguish between truth and falsehood.

Luo Bin, deputy director of the Sichuan Provincial Environmental Monitoring Station, told reporters that the so-called ash is mainly particulate matter, which is divided into three types according to the different particle sizes: one is particles with a particle size of 100 microns; One is PM10, with a particle size of 10 microns; One is that the particle size is microns. These three types of particulate matter are different in the environment, pollution composition, and the time and height of their existence.

Chen Shigong, deputy director of the Ningxia Environmental Monitoring Center Station, introduced that the formation mechanism is that dust, sulfur dioxide, nitrogen oxides and other substances encounter water vapor in the air and form acidic condensation nuclei. From the meteorological point of view and the formation mechanism of condensation nuclei, the so-called ash layer of 9-11 layers does not exist.

Professor Ma Degang, deputy dean of Tianjin University's School of Environmental Science and Engineering, said that in the field of environmental science research, there is no such thing as a rising ash layer, and it is not possible to generalize that the 9th and 11th floors of buildings are the most polluting. "Atmospheric movement is carried out in three-dimensional space, not only vertical movement, but also horizontal movement, taking high-rise buildings as an example, without considering the influence of wind, the convection generated by solar radiation on the yin and yang surfaces is different, so it is difficult to distinguish the distribution of pollutants by floor. ”