How did the smog come from, its harm, and its knowledge.

Haze, as its name implies, is fog and haze. But there is a big difference between fog and haze. The aerosol system composed of dust, sulfuric acid, nitric acid and other particles in the air causes visual impairment, which is called smog. Haze is haze.

Fog is an aerosol system consisting of a large number of tiny water droplets or ice crystals suspended in the air near the ground. It mostly occurs in autumn and winter (which is also one of the reasons for the large-scale haze weather in China in June 20 13), and it is the product of water vapor condensation (or condensation) in the near-surface air. The existence of fog will reduce air transparency and worsen visibility. If the horizontal visibility of the target drops below 1000 meters, the weather phenomenon of water vapor condensation (or condensation) suspended in the air near the ground is called fog.

Haze (mái), also known as haze (smog), dust, sulfuric acid, nitric acid, organic hydrocarbons and other particles in the air can also make the atmosphere turbid. The phenomenon that the horizontal visibility of the target is 1000- 10000 meters is called light fog or mist. When fog is formed, the atmospheric humidity should be saturated (if there are a large number of condensation nuclei, the relative humidity may not reach 100%, and saturation may occur). Because the light scattered by fog composed of liquid water or ice crystals has little to do with wavelength, the fog looks milky white or bluish white and gray.

Haze weather is a state of air pollution, and smog is a general term for all kinds of suspended particles in the atmosphere, especially PM2.5 (particles with aerodynamic equivalent diameter less than or equal to 2.5 microns) is considered as the "culprit" causing haze weather. With the deterioration of air quality, cloudy days are increasing and the harm is increasing. In many areas of our country, the smog weather phenomenon is combined with fog as an early warning and forecast of disastrous weather. Collectively referred to as "haze weather".

human factor

Sources of toxic particles in cities:

First: it's automobile exhaust. Large vehicles that use diesel are "recidivists" who emit PM 10, including buses, shuttle buses of various units and large transport trucks. Sources of toxic particulate matter in cities: firstly, automobile exhaust. Cars that use diesel are "habitual criminals" who emit particles. Small cars that use gasoline emit gaseous pollutants, such as nitrogen oxides, which are easily converted into secondary particulate pollutants in foggy days, aggravating smog.

Vehicle exhaust is the main component of smog particles. According to the latest data, motor vehicle exhaust accounts for 22.2%, coal combustion accounts for 16.7%, dust accounts for 16.3%, and industry accounts for 15.7%. However, with the development of automobile technology and the improvement of oil quality, environmental managers have found that motor vehicle exhaust does not play a decisive role in the formation of haze weather. However, as some cities with large car ownership, managers still need to control vehicle emission standards to avoid the formation of haze weather.

Second: the waste gas produced by burning coal for heating in winter in the north.

Third: the waste gas emitted by industrial production. For example, metallurgy, kilns and boilers, electromechanical manufacturing, automobile repair and paint and building materials production produce a lot of waste gas from kiln combustion.

Fourth: Dust generated by construction sites and road traffic.

Fifth, the particle size of growable particles, bacteria and viruses is equivalent to PM0.1-PM2.5. When the humidity and temperature in the air are appropriate, microorganisms will attach to particles, especially oil fume particles, which will adsorb oil droplets and transform them into more microorganisms, which will increase the growth of biotoxic substances in smog.

6. Dust "smog" will also be produced in home decoration. Indoor dust is pervasive, which is not only harmful to the health of staff and users, but also increases the cleaning burden. When the dust is serious, it also brings many hidden dangers to the decoration project. [3] [4]

In addition to meteorological conditions, the increase of atmospheric particulate matter (including coarse particulate matter PM 10 and fine particulate matter PM2.5) caused by industrial production, vehicle exhaust emissions and coal burning in winter is an important factor of smog. At present, the level of pollutant discharge in many cities is at a critical point, which is very sensitive to meteorological conditions. When the diffusion conditions are good, the air quality can reach the standard, and once adverse weather conditions are encountered, the air quality and visibility will drop immediately.

climatic factor

"There is a difference between fog and haze. Fog refers to the weather phenomenon that the visibility is lower than 1 km due to the condensation of suspended water vapor in the atmosphere; The formation of smog is mainly the result of a large number of suspended particles in the air and meteorological conditions. There are three reasons:

First, the phenomenon of static wind in the horizontal direction has increased.

The higher the buildings are built in the city, the obstruction and friction of airflow passing through the urban area will be obviously weakened. The increase of static wind phenomenon is not conducive to the diffusion and dilution of suspended particles in the atmosphere, and it is easy to accumulate around urban areas and suburbs.

Second, the vertical direction is reversed.

The inversion layer is like a pot cover over a city. This inversion phenomenon that the upper air temperature is higher than the lower air temperature limits the vertical movement of the lower air, making it difficult for suspended particles in the air to drift to the upper air and be blocked at the lower air and near the ground.

Third, the increase of suspended particulate matter and organic pollutants in the air. With the growth of urban population and industrial development, the number of motor vehicles has surged, resulting in a large increase in pollutant emissions and suspended solids.

Fog seems mild, but it contains more than 20 kinds of fine particles and toxic substances harmful to human body, including acid, alkali, salt, amine, phenol and so on. , as well as dust, pollen, mites, influenza virus, tuberculosis, pneumococcus and so on. Its content is dozens of times that of ordinary atmospheric water droplets. Haze is more harmful to people's health than fog. Because the diameter of fine powdery floating particles in smog is generally below 0.0 1 micron, they can directly enter bronchi and even lungs through the respiratory system. Therefore, the biggest impact of smog is the human respiratory system, and the diseases caused are mainly concentrated in respiratory diseases, cerebrovascular diseases, nasal inflammation and other diseases. At the same time, in the haze weather, the air pressure decreases, the inhalable particulate matter in the air suddenly increases, the air mobility is poor, and the diffusion speed of harmful bacteria and viruses to the surrounding area slows down, resulting in an increase in the virus concentration in the air and a high risk of disease transmission.

On February 20-26, 20 14, the severe smog weather lasted for 7 days, which was the longest lasting and the most serious air quality in Beijing in recent years. The hourly concentration of PM2.5 in some stations exceeds 550 micrograms per cubic meter, reaching the upper limit of air quality index AQI evaluation, which is called "exceeding the standard". The evaluation of this kind of air abroad is, "toxic!"

The Comprehensive Scientific Assessment Report of Particulate Matter in the Air issued by the US Environmental Protection Agency in 2009 pointed out that there are enough scientific research results to prove that fine particulate matter in the air can adsorb a large number of carcinogens and genotoxic mutagenic substances, which bring negative effects that cannot be ignored to human health, including increased mortality, aggravation of chronic diseases, deterioration of respiratory and heart diseases, changes in lung function and structure, influences on reproductive capacity, and changes in human immune structure.

According to the statistics of Beijing Municipal Health Bureau, every time there is severe smog weather, the number of patients who come to the respiratory departments of major hospitals in the city will increase by 20-50%. Jean Reno, a French actor who participated in the Beijing International Film Festival and is famous for Murderers Not Too Cold, was admitted to the hospital due to respiratory diseases, and his interview was temporarily cancelled.

More seriously, air pollution will also affect human fertility and the health of infants and young children. Experts say that the fertility of animals exposed to high concentrations of air pollutants in embryo and infancy is significantly lower than that of animals exposed to polluted environment in adulthood.

Gao Rong, deputy director of the Climate and Climate Change Service Office of the National Climate Center, and Zhang Ying, an associate researcher at the Institute of Urban Development and Environment of the China Academy of Social Sciences, said in an interview with the media: "PM2.5 air fine particles have a significant impact on the teratogenic rate and premature delivery rate of infants."

The main hazards of smog can be summarized into two types: one is the harm to human body, and the other is the harm to traffic.

1, harm to human body:

(1) on the respiratory system.

The composition of smog is very complex, including hundreds of atmospheric chemical particles. Among them, aerosol particles smaller than 10 micron are harmful to health, such as mineral particles, sea salt, sulfate, nitrate, organic aerosol particles, fuel, automobile exhaust, etc., which can directly enter and adhere to human respiratory tract and alveoli. In particular, submicron particles will be deposited in the upper and lower respiratory tract and alveoli respectively, causing acute rhinitis and acute bronchitis. For patients with chronic respiratory diseases such as bronchial asthma, chronic bronchitis, obstructive emphysema, and chronic obstructive pulmonary disease, smog weather will make the condition acute or acute. Staying in this environment for a long time will also induce lung cancer.

(2) Effects on cardiovascular system.

Hazy days also have a serious impact on cardiovascular and cerebrovascular diseases, which will hinder normal blood circulation, lead to cardiovascular diseases, hypertension, coronary heart disease, cerebral hemorrhage, and may also induce angina pectoris, myocardial infarction and heart failure. And cause pulmonary heart disease in chronic bronchitis.

In addition, when the air pressure is relatively low in foggy weather, people will feel irritable and their blood pressure will naturally rise. On the other hand, in foggy days, the temperature is often low. Some patients with hypertension and coronary heart disease suddenly go from warm indoor to cold outdoor, and blood vessels expand with heat and contract with cold, which will also increase blood pressure, leading to stroke and myocardial infarction. Therefore, patients with cardiovascular and cerebrovascular diseases must take medicine on time and handle it carefully.

(3) Hazy weather will also lead to the weakening of ultraviolet rays in the surface layer, which can enhance the activity of infectious bacteria in the air and increase infectious diseases.

(4) It is not conducive to children's growth. In foggy days, due to the decrease of sunshine, insufficient ultraviolet radiation for children, insufficient production of vitamin D in the body, and greatly reduced absorption of calcium, rickets in infants and young children will be seriously caused, which will slow down the growth and development of children.

(5) Affect mental health.

Experts point out that continuous foggy days have an impact on people's psychology and body. Psychologically speaking, foggy days will give people a feeling of depression, which will stimulate or aggravate the state of psychological depression. In addition, due to the weak light and low air pressure in foggy days, some people will feel lazy and depressed in foggy days.

(6) affecting reproductive capacity.

Studies have shown that the success rate of sperm in vitro fertilization may be reduced in people who have been exposed to high concentrations of polluted air for a long time. The researchers also found a link between toxic air and the decline of male fertility.

20 13 1 1.5 The Green Paper on Climate Change: Report on Coping with Climate Change (20 13) jointly issued by China Academy of Social Sciences and China Meteorological Bureau pointed out that in recent 50 years, the smog weather in China has generally shown an increasing trend. Among them, the number of foggy days decreased significantly, the number of haze days increased significantly, and the process of persistent haze increased significantly.

[1] Smog weather will have a significant negative impact on climate, environment, health and economy, such as acid rain and photochemical smog in the urban atmosphere, which will lead to a decline in atmospheric visibility and hinder air, water and land traffic; Increase mortality, aggravate chronic diseases, aggravate respiratory and heart diseases, change lung function and structure, affect reproductive capacity and change human immune structure.

2. Harm to ecological environment and traffic:

(1) affects traffic safety.

In foggy days, due to poor air quality and low visibility, traffic jams and traffic accidents are easily caused. In daily driving, you should observe the road conditions to avoid danger.

(2) Hazy weather is more likely to cause cancer.

In foggy days, the light is seriously insufficient, the ultraviolet rays near the bottom are obviously weakened, and the bacteria in the air are difficult to kill, thus greatly increasing the probability of infectious diseases. Zhong Nanshan, academician of China Academy of Engineering and director of Guangzhou Institute of Respiratory Diseases, once pointed out at a forum that in the past 30 years, the smoking rate of the public in China has been declining, but the prevalence of lung cancer has increased more than four times. This may be related to the increase in haze days. Not only foggy days with very low visibility will have an impact on human health, but also foggy days and cloudy days will have the same problem.

(3) Affect the ecological environment.

Haze weather has an important impact on roads, railways, aviation, shipping, power supply systems and crop growth. Fog and haze will cause air quality decline, affect the ecological environment and bring great harm to human health.