In haze weather, which pollution is more serious, high altitude or low altitude?
The inversion layer is like a "big pot lid"
Detaining pollutants at low altitudes
How can the blue sky and white clouds at high altitudes and the haze at low altitudes appear at the same time? ?
Under normal weather conditions, the higher the altitude, the lower the temperature. In this way, the cold air at high altitudes is relatively dense and heavier than the warm air below. The sinking of cold air causes the warm air to rise. This creates an alternating circulation process of vertical airflow, causing low-altitude pollutants to begin to rise vertically upward with the airflow, and spread to the surroundings at high altitudes.
But in winter, when the temperature suddenly rises, there is a clear breeze or windless day, and there is a breeze at night, this normal circulation system will be "broken". After the low-altitude air close to the ground cools down sharply, the air above it cools slowly, resulting in a situation of "cold below and hot above". This creates an inversion layer of atmospheric flow.
The air is "heavy at the bottom and light at the top", resulting in poor fluidity and not conducive to the diffusion of pollutants. Such an inversion layer is like an invisible "big pot lid" that tightly covers the low altitude of Shenyang, while pollutants such as industry, motor vehicles, heating coal emissions, and construction site dust in the low altitude cannot diffuse and flow out. Gathering increases pollution.
At the same time, low-altitude air near the ground in cities absorbs a large amount of pollutant emissions. Generally, the chimney heights of large heat source plants, thermal power plants and large industrial and mining enterprises are more than 200 to 300 meters, which can directly remove pollution. The material passes through the "big pot lid" and is discharged to high altitude for diffusion. However, there are a huge number of pollution point sources such as small heating chimneys, construction site dust, ground dust, motor vehicle exhaust, and catering fumes at low altitudes, and the total emissions are large, all of which are concentrated in low altitudes.
This will cause high-altitude blue sky and low-altitude haze pollution. Only after a cold air passes through and the "big pot lid" is lifted can the pollution spread out.
Analysis of the causes of haze pollution and its control measures
Recently, there have been overwhelming reports about haze weather and air pollution. With the advancement of China's urbanization process, haze has become a common environmental disaster in cities, especially first-tier cities with rapid economic development. In fact, haze weather is not unique to these years. Winter and early spring are the peak periods of haze. However, in recent years, this haze pollution phenomenon has become more and more serious. We cannot blindly only see the problems caused by urbanization, ignore ourselves, and blindly blame the country or the government. We must combine the unfavorable meteorological conditions that form the determining factor of haze, calmly analyze the essential factors causing haze due to man-made pollution, alleviate the public’s doubts about haze, and find out measures and ways to effectively control this pollution as soon as possible.
Causes and harms of haze pollution
Characteristics of haze weather
From a meteorological perspective, fog and haze are two different weather phenomena. Fog is close to the ground layer, has a low height, and is generally composed of tiny water droplets in the air layer below 400 m. Fog reduces air transparency and worsens visibility. From a physical perspective, fog and clouds are both products of condensation of water vapor in the air, and there is a clear boundary between them and the clear sky area. When fog occurs, the atmospheric humidity reaches saturation. When the fog reaches a certain height, it becomes a cloud. When the cloud lowers 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. The diameter of fog droplets is usually larger, from a few microns to 100 μm, with an average diameter of about 10 μm ~ -20 μm. , so you can see the fog droplets floating in the air with the naked eye. Since fog scatters sunlight and has little relationship with the wavelength of light, the fog we generally see is milky white or bluish white.
The main components of haze are tiny particles such as H2SO4 and HNO3. The thickness of haze is relatively large, reaching 1 km to 3 km. The difference between haze and fog is that the relative humidity of haze is low. Generally, the weather phenomenon that worsens atmospheric visibility when the relative humidity is less than 80% is haze, while the relative humidity is greater than When the relative humidity is 90%, it is fog. 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 has no clear boundary with the clear sky area. The distribution of haze particles is uniform, and the particle diameter is small, ranging from 0.001 μm to 10 μm, with an average diameter of about 1 μm to 2 μm, so the particles floating in the air cannot be seen by the naked eye. Haze composed of dust, H2SO4, HNO3 and other particles easily scatters light with longer wavelengths, so haze is usually yellow or orange-gray.
Causes of haze pollution
a) The phenomenon of static wind in the horizontal direction of the atmosphere increases. In recent years, urbanization has developed rapidly and urban land is in short supply. As a result, building heights have become higher and higher, and building density has increased. As a result, the wind force is weakened due to the obstruction and friction of buildings when passing through the city, and the static wind in the horizontal direction is weakened. The increase in wind phenomena is not conducive to the diffusion of atmospheric pollutants in cities, leading to the accumulation of pollutants in the atmosphere and the formation of haze;
b) The phenomenon of atmospheric temperature inversion in the vertical direction increases.
The inversion layer is like a pot lid covering the city. The inversion phenomenon in which the upper air temperature is higher than the lower air temperature will limit the vertical movement of low-altitude air. It also hinders the diffusion of atmospheric pollutants and stays near the ground, forming haze;
c) Increase in air pollutants and suspended particulate matter. This is the main and most direct cause of haze pollution. With the advancement of China's urbanization process, the urban population has increased dramatically, the number of private cars has increased, and industry has continued to develop, which has led to an increase in suspended particulate matter and atmospheric pollutants emitted by humans into the atmosphere. What we usually call PM2.5 refers to particulate matter in the atmosphere with a diameter less than or equal to 2.5 μm, also known as particulate matter that can enter the lungs. Its diameter is only 1/20 of the thickness of a human hair. PM2.5 is only a small part of the atmospheric composition, but it seriously affects the city's air quality and atmospheric visibility. The soluble particles in PM2.5 are highly water-absorbent. When they are absorbed by water vapor in the atmosphere, they will form haze weather.
The serious harm of haze pollution
Impact on human health
From the above analysis of haze components, we know that PM2.5 is very harmful to human health. It will enter the human respiratory tract and lungs. Living in haze will cause people to have a series of adverse reactions such as coughing, sleepiness, and nausea. If this pollution is not controlled, it may even induce lung cancer in the long run. In addition, haze will also weaken the ultraviolet radiation on the surface, enhance the activity of infectious bacteria, and accelerate infection. In addition, haze can also seriously affect people's mental health. Gray weather can make people depressed and irritable, and the possible serious consequences of haze can also cause people to have negative emotions such as anxiety and fear.
The probability of forming acid rain increases
Acid rain has always been feared by people, and it is also inseparable from haze. Therefore, what we need to control more is the fog that may cause acid rain. Haze weather. The essence of haze pollution is actually the pollution of harmful suspended particulate matter. The main sources of such particles are industrial combustion waste and automobile exhaust. The secondary particulate pollutants formed by these gases through chemical reactions in the atmosphere are more toxic. A research team from Tsinghua University in Beijing has collected and analyzed the haze in Beijing. The main components of the liquefied haze water are H2SO4, NO2 and other acidic substances, and the color is turbid or even black. This kind of acid fog is no less harmful than acid rain.
Causing traffic accidents
Haze weather has seriously affected the air quality and atmospheric visibility in the region, making it inconvenient for citizens to travel and driving safety is seriously threatened. When driving, the vision is affected by haze, which directly leads to traffic congestion and traffic accidents.
Measures for the control and treatment of haze pollution
Declaring war on haze pollution is a focus issue related to people’s livelihood. There are complex reasons for the formation of smog, and governance is a long-term process. Governments, businesses, and people must join in this fight to reduce energy consumption and pollution.
Control measures for haze weather
The process of controlling haze cannot be rushed. We must first reduce the harm of haze. a) The prediction of haze weather should be strengthened to lay a defense for society and the people so that corresponding measures can be taken in time to deal with haze weather. Predictions will also facilitate government departments to implement dynamic regulation; b) The main causes of haze should be analyzed Strengthen control of pollution sources: control the number of motor vehicles to reduce exhaust emissions; urge industrial enterprises to improve technology and reduce exhaust emissions; control people's coal-burning pollution and festival fireworks pollution; c) Relevant departments should actively carry out in-depth research on haze control , analyze in detail the controllable causes of haze, and propose countermeasures in a timely manner.
Countermeasures for the management of haze weather
a) The primary measure to control haze weather is to strengthen the implementation of the concept of environmental protection in the whole society. The formation of smog weather reflects that in the process of urbanization, China has neglected the protection of the ecological environment and resources while developing its economy. Therefore, we must pay attention 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 pursue economic development alone. This is the most basic way to control haze weather. Thoughts;
b) Areas with severe haze should actively carry out PM2.5 prevention and control activities, conduct in-depth research on the specific causes of PM2.5 in the region, seize the root causes of air pollution, study countermeasures, and promote the prevention and control of PM2.5 in the region. Establish air pollution regulations, formulate prevention and emergency plans, and establish a complete PM2.5 monitoring and evaluation assessment system. Carry out comprehensive management of key pollution areas causing haze;
c) Promote the construction of urban green space systems. Plants can absorb harmful substances in the atmosphere to a certain extent, effectively purify the air and help control haze weather. Urban planning departments should cooperate with government departments to actively promote the construction of green space systems in urban centers. In addition, agricultural and forestry research departments should also join the team to control smog, conduct in-depth research on plant varieties that can effectively purify the air, and introduce them into the construction of urban green spaces.
Smog is an important issue related to people’s livelihood. The causes of haze weather are complex, and the governance process cannot be accomplished overnight. Government departments and business units must change the traditional concept of development and adhere to the green and sustainable approach. development path, and urban residents must also pay enough attention to this, understand their unshirkable responsibilities in the process of fighting smog, and reduce domestic waste gas emissions. Only with the active participation and joint efforts of the whole people can we achieve the important goal of controlling haze weather and improving air quality.