How to write smog in popular science composition?

Haze is a kind of composite fine-particle suspended matter, with a particle size ranging from PM0. 1 to PM2.5, collectively referred to as 2.5 micron fine particles. Under the condition of stable atmosphere, this mixed suspended substance can be suspended from the ground to a height of 500 meters for several days or even weeks. In windy conditions, the height is uncertain. When it rains, it will soon sink and disappear.

This fine particle itself cannot be blocked by nose hair, cilia and alveoli. After inhalation, it will directly enter the blood through exchange, which will have an impact on human health. According to the research data of WHO (World Health Organization), the incidence of lung cancer increases by 4% every time the air pollution index rises by 10PPM (one in a million), and it is also positively correlated with respiratory irritation and allergy. It also has an impact on children's heavy metals exceeding the standard (most of the urban smog is industrial pollution, tail gas emissions, catering emissions and so on. )

Since 20 12, the health panic caused by smog and PM2.5 in big cities and eastern cities of China has attracted public attention. Haze and photochemical smog lead to longer-term and more dangerous environmental conditions, and the public will pay more attention to health protection measures.

Haze, as its name implies, is fog and haze. Fog is the water droplets floating in the air after the water vapor close to the ground meets the condensation of cold air under specific climatic conditions, and moves and dissipates with the change of wind and temperature. The normal fog itself is white, which appears when the air has high water content and low temperature.

Haze is smoke mixed with a lot of ash impurities, which is called haze. When the water vapor content in the air is not high, the visibility drops sharply. Recently, most of the smog that pervades the whole eastern and central China is grayish white or grayish yellow. Sulfur dioxide, nitrogen oxides and inhalable particles in air pollutants are the main components of smog. The first two are gaseous pollutants, and the last one is the chief culprit that aggravates smog weather pollution. Among them, inhalable particulate matter is the general name of all kinds of particulate matter with a diameter less than or equal to 10 micron. Common particles are PM 10 and PM2.5, which refer to atmospheric particles with diameters less than or equal to 10 micron and less than or equal to 2.5 micron respectively.

This fine particle is also an air pollutant. They are suspended in the air, which not only blocks the view and reduces the visibility, but also absorbs other pollutants in the air as carriers, such as organic pollutants that combine with water mist to form aerosols, such as industrial emission compounds, smoke and dust, automobile exhaust, etc., and further reacts with sunlight to form a more harmful pollution mixture.

Where does the smog come from?

It is generally believed that the sources of smog are industrial emission pollution, urban construction and decoration, road dust, domestic heating and smoke exhaust and automobile exhaust. Haze contains fine dust, volatile acid fog such as nitric acid and sulfuric acid, organic hydrocarbons and heavy metals. And this is the main component of air pollutants, dust and automobile exhaust in heavy industry. In particular, coal-fired thermal power generation, steelmaking and ironmaking metallurgy, chemical industry and wood processing and building materials industries with concentrated dust are one of the main sources of atmospheric particulate matter and sulfide. Most of the automobile exhaust is nitrogen oxides and carbon oxides, especially the particulate matter content in diesel automobile exhaust is larger.

If we look at smog from a broader perspective, we can find some historical laws, that is, almost all developed countries have experienced a period of serious smog pollution in the process of industrialization. London, the most famous foggy city, has a history of 200 years, and even formed the brand of "London Fog". Since the industrial revolution, the smog in big cities in Britain such as London has formed and developed to a serious degree. 1952 There was even a smog event in London:1February 5-9, 952, the inversion layer enveloped London, and the city was at the center of high pressure. The vertical and horizontal airflow stopped and the air was silent for several days. At that time, London used coal for heating in winter, and there were many coal-fired power stations in the urban area. Gases and pollutants such as carbon dioxide, carbon monoxide, sulfur dioxide, dust and so on produced by coal combustion accumulate over the city, causing foggy weather for several days. During the period, affected by poisonous fog, not only a large number of flights were cancelled, but even cars had to turn on their headlights when driving on the road during the day. The indoor concert was also cancelled because people couldn't see the stage. Londoners also responded to the poisonous fog. Many people feel difficult to breathe and their eyes sting. The number of patients with respiratory symptoms such as asthma and cough has increased significantly, and the sudden increase in mortality has led to as many as 12000 people dying from air pollution, which has promoted the process of environmental protection legislation in Britain.

However, with the completion of industrialization in Britain, urban construction has basically reached saturation, and basic industries have gradually withdrawn from the local area. After years of environmental management, we know that the fog in London has returned to normal in the past decade, and the once world-famous smog weather is rare in Britain.

In the same period of US 1948, Donola, a small town in Pennsylvania, located 30 kilometers south of Pittsburgh, had more than 14000 residents. Donola Town is the concentration place of sulfuric acid plant, steel plant and zinc smelting plant. For many years, the chimneys of these factories have been spraying smoke into the air, so that the residents of Donora town have become accustomed to the strange smell in the air. 1948101October 26 -3 1 day, the angel town of Donora is particularly dark with continuous fog. The climate is humid and cold, the sky is overcast, there is no wind, and the air loses its vertical movement, resulting in inversion. In this dead wind state, the chimney of the factory did not stop discharging, just like breaking through the frozen atmosphere and constantly spewing smoke. There is a pungent smell of sulfur dioxide (SO2) in the air, which is disgusting. The visibility of the air is extremely low, and all factories except chimneys disappear into the smoke. Subsequently, 6000 people in the town suddenly became ill, with symptoms such as eye disease, sore throat, runny nose, cough, headache, limb weakness, chest tightness, vomiting and diarrhea. Twenty of them died soon. Most of the deceased were over 65 years old, and most of them had suffered from heart disease or respiratory diseases, similar to the Mas Valley incident that year. The main reason of this smog event is that the gas and metal particles containing toxic and harmful substances such as sulfur dioxide emitted by factories in small towns gather in the valley under abnormal climate. These toxic substances are attached to suspended particles, which seriously pollutes the atmosphere. People inhale a lot of these toxic gases in a short time, causing various symptoms and sudden diseases.

Similarly, in the United States, the photochemical smog incident in Los Angeles is one of the world-famous public hazards, which occurred in Los Angeles in the early 1940s. Photochemical smog is produced by the reaction of a large number of hydrocarbons with other components in the air under the action of sunlight. This kind of smog contains oxidants such as ozone, nitrogen oxides and acetaldehyde, and it stays in the urban area for a long time. In a photochemical smog incident in June 5438+February 0952 +65438, more than 400 people over 65 years old in Los Angeles died. 1September, 955, due to air pollution and high temperature, more than 400 elderly people over 65 died in just two days, and many people developed symptoms such as eye pain, headache and difficulty breathing. Until the 1970s, Los Angeles was called "the Smoky City of America". In the 1940s, there were 2.5 million cars in Los Angeles, which consumed about11000 tons of gasoline every day and emitted more than1000 tons of hydrocarbons (CH), more than 300 tons of nitrogen oxides (NOx) and more than 700 tons of carbon monoxide (CO). In addition, there are other oil burning emissions from refineries and oil supply stations. These compounds are discharged over sunny Los Angeles, forming a toxic smoke factory. This kind of smoke makes people's eyes red, their throats ache, they feel suffocated, dizzy and have a headache. This kind of smog is caused by the emission of automobile exhaust and industrial waste gas, which usually occurs at noon or afternoon in summer with sunny sunshine, low humidity and temperature of 24-32℃. Olefins and nitrogen dioxide (NO2) in automobile exhaust are discharged into the atmosphere, which will absorb the energy of sunlight under strong ultraviolet irradiation. The molecules of these substances will become unstable after absorbing the energy of sunlight, and the original chemical chain will be destroyed to form new substances. This chemical reaction is called photochemical reaction, and its product is highly toxic photochemical smog.

In Asia, in 197 1 year, a serious photochemical smog incident occurred in Tokyo, Japan, causing some students to faint from poisoning. On the same day, similar incidents occurred in other cities in Japan. Since then, photochemical smog has appeared continuously in some big cities in Japan. After investigating the main pollutants emitted by several major pollution sources in Tokyo, the Japanese environmental protection department found that CO, NOx and HC emitted by automobiles accounted for about 80% of the total emissions.

To sum up, industrial emissions and automobile exhaust constitute the most important hazards in smog pollution. With the saturation of industrialization development in major developed industrialized countries, the pollution industry gradually withdrew from the local area, the awareness of environmental protection was enhanced, the process of atmospheric environmental control was accelerated, and such serious pollution incidents gradually decreased and disappeared. At present, China is in a critical period of industrialization, and the development of basic industries, processing industries and fine industries is booming simultaneously. Especially since the reform and opening up more than 30 years ago, the process of urbanization has been accelerated, automobiles have been popularized, China has entered the ranks of quasi-developed countries, and people's demand for industrial products and services and energy consumption have been increasing. A large number of needed basic industries, untreated small factories and backward overcapacity coexist, which has caused great pressure on the atmospheric environment. Because China's industrialization started late in the world's major industrialized countries, but it has developed rapidly, China's industrial capacity has doubled several times in just a few years, and the subsequent industrial pollution and the rapid popularization of automobiles have brought about exhaust pollution faster and even greater than the problems experienced by industrialized countries.

How harmful is smog?

According to recent research, the World Health Organization identified air pollution as "carcinogenic to human beings" for the first time, and regarded it as a universal and major environmental carcinogen. This statement was issued by the International Agency for Research on Cancer under the World Health Organization. The International Agency for Research on Cancer in Lyon, France, said in its report that there is sufficient evidence that exposure to outdoor air pollution will lead to lung cancer and the risk of bladder cancer will increase accordingly. Experts from this institution held a week-long meeting, reviewed more than 1000 latest works from research institutions on five continents around the world, and finally made a determination.

China Academy of Social Sciences and China Meteorological Bureau jointly issued the Green Paper on Climate Change, which reported that smog weather affects health, which not only aggravates diseases of respiratory system and heart system, but also affects reproductive capacity. At present, the most direct harm of smog to human health is mainly to increase the incidence of respiratory diseases. Hazy weather has an acute impact on health, mainly manifested as symptoms of upper respiratory tract infection, asthma, conjunctivitis, bronchitis, eye and throat irritation, cough, dyspnea, nasal congestion and runny nose, rash, cardiovascular system disorder and other diseases. The incidence/hospitalization rate of respiratory diseases has increased. In addition, smog weather will have some indirect effects on human health. Haze will weaken ultraviolet radiation. If smog often occurs, it will affect the synthesis of vitamin D in human body, lead to a high incidence of rickets in children and enhance the activity of infectious bacteria in the air. Smog weather will also affect people's mental health, making people depressed and pessimistic.

Photochemical smog, a by-product of smog, can be said to have accumulated highly toxic carcinogens, which is the most harmful to human health.