Low-altitude retained pollutants

How can the blue sky and white clouds at high altitude and the smog at low altitude appear at the same time?

Under normal weather conditions, the higher the space height, the lower the temperature, so that the relative density of cold air above the sky is higher and heavier than that of warm air below. The cold air sinks to push the warm air to rise, which leads to the process of alternating vertical airflow, which makes the pollutants at low altitude start to rise vertically with the airflow and spread around at high altitude.

However, such a normal circulation system will be "broken" on sunny days, windless days and breezy nights when the temperature suddenly rises in winter. After the low-altitude air near the ground drops sharply, the high-altitude air drops slowly, resulting in a "cooling down and heating up" situation, which leads to the inversion layer of atmospheric flow.

The air is "heavy on the bottom and light on the top", which leads to poor fluidity and is not conducive to the diffusion of pollutants. Such an inversion layer is like an invisible "big pot cover", which tightly covers Shenyang at low altitude, while pollutants such as low-altitude industries, motor vehicles, heating coal emissions, and construction site dust cannot spread out, and gather at low altitude to aggravate pollution.

At the same time, the low-altitude air near the ground in the city receives more pollutants. Generally, the chimneys of large heat source plants, thermal power plants and large industrial and mining enterprises are all above 200 to 300 meters high, so that pollutants can be directly discharged into the sky through the "big pot cover" for diffusion. However, there are a large number of pollution point sources such as low-altitude small and medium-sized heating chimneys, construction site dust, ground dust, motor vehicle exhaust, oil smoke and so on. And the total amount of emissions is large, so they all gather at low altitude.

In this way, there will be high-altitude blue sky and low-altitude smog pollution. Only after a cold air crossing can the "big pot cover" be opened to spread pollution.

Cause analysis and control measures of smog pollution

Recently, reports about smog weather and air pollution have been overwhelming. With the development of urbanization in China, smog has become a common environmental disaster in cities, especially in first-tier cities with rapid economic development. In fact, smog weather is not unique to these years. From winter to early spring is the high incidence of smog. However, in recent years, this smog pollution phenomenon has become more and more serious. We can't just see the problems brought by urbanization, but ignore ourselves and blame the country or the government blindly. It is necessary to calmly analyze the essential factors of smog caused by man-made pollution in combination with the decisive factor of unfavorable meteorological conditions, so as to alleviate people's doubts about smog and find effective measures and ways to control this pollution as soon as possible.

Causes and harm of smog pollution

Characteristics of haze weather

From the meteorological point of view, fog and haze are two different weather phenomena. The fog is close to the ground layer and the height is low. It is generally composed of tiny water droplets in the gas layer below 400 meters ... fog will reduce air transparency and visibility. From the physical point of view, fog and clouds are the products of condensation of water vapor in the air, which has obvious boundaries with clear sky areas. When fog appears, the atmospheric humidity reaches saturation, when the fog rises to a certain height, it becomes a cloud, and when the cloud falls to the ground, it is called fog. Fog usually has uneven concentration distribution and small thickness. The thickness of common radiation fog is about tens of meters to 200 meters, while the diameter of fog drops is usually large, from a few microns to 100 micron, and the average diameter is about 10 micron to -20 micron, so the naked eye can see the fog drops floating in the air. Because fog has little to do with the wavelength of light when scattering sunlight, the fog we usually see is milky white or bluish white.

The main components of smog are tiny particles such as H2SO4 and HNO3. The thickness of haze is relatively large, which can reach 1 km ~ 3 km. The difference between haze and fog is that the relative humidity is low. When the relative humidity is less than 80%, the weather phenomenon that the atmospheric visibility becomes worse is haze, while when the relative humidity is more than 90%, it is fog, and when the relative humidity is between 80% and 90%, it is a mixture of haze and fog, but the main component is haze. Haze is different from fog and clouds, and there is no obvious boundary between haze and clear sky. Smog particles are evenly distributed, and the particle size is small, ranging from 0.00 1 micron to 1 micron, with an average diameter of about1micron to 2 microns to 2 microns. No floating particles can be seen by naked eyes. Haze composed of dust, H2SO4, HNO3 and other particles is easy to scatter light with longer wavelength, so the haze is usually yellow or orange-gray.

Causes of smog pollution

A) The phenomenon of static wind in the horizontal direction of the atmosphere is increasing. In recent years, with the rapid development of urbanization and the shortage of urban land, the building height is getting higher and higher, and the building density is getting bigger and bigger, which makes the wind weaken when passing through the city due to the blocking and friction of buildings, and the horizontal static wind phenomenon increases, which is not conducive to the diffusion of atmospheric pollutants in the city, leading to the accumulation of atmospheric pollutants and the formation of smog;

B) The phenomenon of atmospheric inversion in the vertical direction increases. The inversion layer is like a pot cover above the city. The inversion phenomenon of high-altitude temperature higher than low-altitude temperature will limit the vertical movement of low-altitude air, and also hinder the diffusion of atmospheric pollutants, and stay near the ground to form smog.

C) air pollutants and suspended particles increase. This is the most important and direct cause of smog pollution. With the advancement of China's urbanization process, the urban population has increased sharply, the number of private cars has increased, and the industry has continued to develop, all of which have led to the increase of suspended particulate matter and air pollutants discharged into the atmosphere by human beings. What we usually say about PM2.5 refers to particles with a diameter less than or equal to 2.5 microns in the atmosphere, which is also commonly known as particles that can enter the lungs. Its diameter is only 1/20. PM2.5, which is only a small part of the atmospheric composition, seriously affects the city's air quality and atmospheric visibility. Soluble particles in PM2.5 have strong water absorption, and they are absorbed by water vapor in the atmosphere, which will form haze weather.

The serious harm of smog pollution

Affect human health

From the above analysis of smog components, we know that PM2.5 is very harmful to human health. It will enter the human respiratory tract and lungs. Living in smog can cause a series of adverse reactions such as cough, drowsiness and nausea. If this kind of pollution is not controlled, it will even induce lung cancer in the long run. In addition, smog will also weaken the ultraviolet radiation on the surface, enhance the activity of infectious bacteria and accelerate infection. In addition, smog will seriously affect people's mental health. Gray weather will lead to people's depression and restlessness, and the possible serious consequences of smog will also cause people's anxiety and fear.

The probability of forming acid rain increases.

Acid rain has always been feared by people, and it is also related to smog, so what we need to control more is the smog weather that may lead to acid rain. The essence of smog pollution is actually the pollution of harmful suspended particles, which mainly comes from industrial combustion waste and automobile exhaust. The secondary particulate pollutants formed by the chemical reaction of these gases in the atmosphere are more toxic. The research group of Beijing Tsinghua University collected and analyzed the smog in Beijing. The main components of liquefied fog water are acidic substances such as H2SO4 and NO2, and the color is turbid or even black. This acid fog is no less harmful than acid rain.

Causing a traffic accident

Haze weather has seriously affected the air quality and atmospheric visibility in this area, which has brought inconvenience to citizens and seriously threatened driving safety. When driving, the vision is directly affected by smog, which leads to traffic congestion and traffic accidents.

Control and treatment measures of smog pollution

Declare war on smog pollution, the focus of people's livelihood. The formation of smog has complicated reasons, and governance is a long-term process. No matter the government, enterprises or people, they must join the war of resistance to reduce energy consumption and pollution.

Control measures of haze weather

The process of controlling smog cannot be rushed, and the harm of smog must be reduced first. A) The forecast of haze weather should be strengthened to lay a defense needle for the society and the people, so as to take corresponding measures in time to deal with haze weather. With the forecast, it is convenient for government departments to implement dynamic regulation; B) Strengthen the control of the main pollution sources that cause smog: control the number of motor vehicles and reduce exhaust emissions; Urge industrial enterprises to improve technology and reduce exhaust emissions; Control people's coal pollution and fireworks pollution in festivals; C) Relevant departments should actively carry out in-depth research on smog control, analyze the controllable causes of smog in detail, and put forward countermeasures in time.

Countermeasures for controlling haze weather

A) The primary measure to control haze weather is to strengthen the implementation of environmental protection concept in the whole society. The formation of haze weather reflects that China has neglected the protection of ecological environment and resources while developing its economy in the process of urbanization. Therefore, we must attach importance to the seriousness of this problem, establish a green, healthy and sustainable development concept in the whole society, actively pursue the comprehensive and coordinated development of economy and ecology, and no longer simply pursue economic development. This is the most basic idea to control smog weather;

B) Areas with severe smog should actively carry out prevention and control activities of PM2.5, thoroughly study the specific causes of PM2.5 in this area, grasp the root causes of air pollution, study countermeasures, promote the construction of air pollution laws and regulations in this area, formulate prevention and emergency plans, establish and improve the monitoring, evaluation and assessment system of PM2.5, and comprehensively control key polluted areas that cause smog;

C) Promote the construction of urban green space system. Plants can absorb harmful substances in the atmosphere to a certain extent, effectively purify the air, and help to control smog weather. Urban planning departments should cooperate with government departments to actively promote the construction of green space system in urban central areas. In addition, agricultural and forestry scientific research departments should also join the team to control smog, deeply study plant varieties that can effectively purify the air, and introduce urban green space construction.

Haze is an important issue related to people's livelihood. The causes of haze weather are complicated, and the treatment process is even more impossible. Government departments and enterprises should change the traditional development concept and stick to the road of green and sustainable development. Urban residents must also pay enough attention to this, understand their unshirkable responsibilities in the process of fighting smog, and reduce the emission of domestic waste gas. Only with the active participation of the whole people and the concerted efforts of Qi Xin, can we achieve the important goal of controlling smog weather and improving air quality.