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Photochemical smog incident in Los Angeles, USA

1943 photochemical smog incident in Los Angeles, USA. Los Angeles is located on the southwest coast of the United States and faces the sea to the west, which is photochemical pollution.

Surrounded by mountains, it is a sunny place with a warm climate and pleasant scenery. The early development of gold mines, oil and canals, coupled with its unique geographical location, quickly made it a port city with developed commerce and tourism. Los Angeles soon became unprecedented prosperity, and the famous Hollywood Film Center and the first "Disneyland" in the United States were built here. The prosperity of the city has increased the population of Los Angeles. During the day, the criss-crossing cities in expressway are crowded with millions of cars, and the whole city is like a giant ant nest. However, the good times did not last long. From the early 1940s, people found that the city changed its gentleness and became "crazy". Every year from summer to early autumn, as long as it is sunny, there will be a light blue smoke over the city, which will make the whole city turbid. This kind of smoke makes people's eyes red, their throats ache, they feel suffocated, dizzy and have a headache. After 1943, the smog became more rampant, so that the pine forest on the 2000-meter-high mountain far away from the urban area 100 km died in a large area, and the citrus production was reduced. Only in the period of 1950- 195 1 year, the loss caused by air pollution in the United States reached1500 million dollars. From 65438 to 0955, more than 400 people over 65 died of respiratory failure. In 1970, about 75% of the citizens suffer from pinkeye. This is the earliest new air pollution event-photochemical smog pollution event. There were 250 photochemical pollutions in Los Angeles in the 1940s.

Ten thousand cars COnsume about 1 100 tons of gasoline every day, and emit more than 1000 tons of hydrocarbons (CH), more than 300 tons of nitrogen oxides (nitrogen oxides) 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. Photochemical smog can be said to be a hidden danger in big cities with developed industries and crowded cars. Since 1950s, photochemical smog events have occurred in many cities in the world. The formation mechanism of photochemical smog is very complicated, and its main pollutants come from automobile exhaust. Therefore, at present, people are actively trying to improve the urban traffic structure, improve automobile fuel, and install catalytic devices in the automobile exhaust system to prevent problems before they happen.

London fog and haze incident in Britain

The London smog incident is one of the world-famous public hazards. This happened in London, England from February 5 to 8. February 3rd is a lovely winter day in London, England. The meteorological observatory reported that a cold front had passed at night; By noon, the temperature reached 5.6℃ and the relative humidity was about 70%. The wind blowing from the north is very comfortable. The sky is dotted with fluffy cumulus clouds, which are famous in Britain when the weather is clear. In a word, the weather is fine today. Old people and patients are particularly happy. They sat in the sun and drank tea against the fresh wind blowing from the North Sea. The wind blew all over England, blowing away all the smoke from the chimneys of factories and urban residents in the central region. London is in a huge anticyclone, which is the southeast edge of the high pressure area. The wind blows clockwise around this high pressure center. On February 4th, 65438, this anticyclone moved southeast along the usual path, with its center several hundred kilometers west of London. The wind turned slightly, blowing from the north-northwest direction, and the wind speed was slower than before. Several layers of clouds almost covered the sky, and through the gap of the wide and uniform dark gray layer clouds at the lower level, we can see that there are still high clouds at an altitude of about 3000 meters. They cover the sun and the sky. At noon, the temperature is 38 F and the relative humidity is 82%. The air is full of smoke. Soot and ash particles from thousands of chimneys quietly drifted into the atmosphere. Large particles fall on roofs, streets, hats and clothes. Smaller smoke floats with the air. When the children were running in and out of the house, a gust of wind brought smoke and gas into the room. Smoke even has its own way to enter the house with closed doors and windows: when the indoor and outdoor temperatures change, the house "inhales" polluted outdoor air and "exhales" clean indoor air. However, considering all the factors, the weather on 65438+February 4th was not too bad, but it was worse than the day before. In the next few days, only people in London knew how bad the weather was. On February 5, 65438, the center of high pressure almost moved over London. The wind is weak, and fog reduces visibility, making it difficult for people to walk. At noon, the temperature is 33 degrees Fahrenheit and the relative humidity is about 80%. The smell of smoke is getting stronger. The wind is too weak to blow away the smoke in the chimney. Photochemical pollution caused by smoke and moisture

Gathered in the atmosphere thousands of meters above the ground. People began to complain to their neighbors, and car drivers mumbled curses into the thick fog. 65438+February 6, the situation is even worse. Thick fog enveloped the whole sky, and the city was located at the western end of the anticyclone. At noon, the temperature dropped to -2℃, the relative humidity rose to 100%, and the atmospheric visibility was only a few tens of feet. All flights of the plane have been cancelled, and only the most experienced drivers dare to drive on the road. Pedestrians groped their way on the sidewalk. The anemometer does not turn and the reading is zero. Because the airflow is too slow to turn the rotor of the anemometer, the wind speed does not exceed two or three kilometers per hour. Sometimes an almost imperceptible breeze blows to the other side. When the air stagnates and floats over the city, boilers in factories, fireplaces in homes and other smoking stoves will add toxins to the air. Fog droplets are mixed with some gases and particles in the smoke. Fog is no longer clean fog or clean water droplets, but a mixture of smoke and fog, which we call "smoke". Smoke fills the city and attacks all living things. When people's eyes feel it, tears will flow down their cheeks. Every time you breathe, you inhale polluted gas from one lung. Where there is a crowd, you can hear coughing. The lecturers in the school had to raise their voices to transcend the dry photochemical pollution.

Cough and asthma. The first to respond to this abnormal situation was a group of award-winning cows that were about to be exhibited in London at that time. They showed difficulty breathing and stuck out their tongues. One of them died immediately, and another 65,438+02 cows had to be sent to the slaughterhouse because of illness. 10 The weather in London still hasn't improved on February 7th and 8th. The smoke is terrible. Old people and patients who enjoyed the refreshing breeze from the north a few days ago now find it very difficult to breathe in this polluted air. Even some young people feel uncomfortable, and it is more difficult for people with respiratory diseases to let oxygen into their lungs. For asthma patients, this kind of smoke is simply a torture. Hospitals in London are crowded with patients, all of whom are victims of smog, and many people have died as a result. On February 9, 65438, the weather improved slightly. The fog still exists, but the wind has been blowing gently from the south. Some clean air mixed with smoke diluted the original smoke. At noon, the temperature is 3℃ and the relative humidity is 95%. 65438+February 10, a cold front passed through England. A strong westerly wind brought air from the North Atlantic. People's lungs breathe fresh and clean air again. At this time, everyone lamented photochemical pollution.

1, relax. Recalling those five days (including 65438+February 9) is like having a nightmare. According to statistics afterwards, during the smog period (65438+February 5-8), the number of deaths in four days was about 4000 more than that in the same period of normal years. The largest number of deaths is over 45 years old, about three times as much as usual; /kloc-the number of children under 0/year old is about twice as high as usual. The deaths from bronchitis, coronary heart disease, tuberculosis and heart failure in the week before the incident were 9.3 times, 2.4 times, 5.5 times and 2.8 times respectively. The mortality rate of patients with pneumonia, lung cancer, influenza and other respiratory diseases has doubled. In addition to death, thousands of people are seriously ill, and some people have caused respiratory diseases. These people have not been counted. In addition, the number of victims should also include patients and relatives of the deceased. Although they survived, their lives were changed by their losses. In any case, it must be a catastrophe. Photochemical pollution of huge smog in London

It happens because the humid and foggy air stagnates over the city, the temperature rises reversely, the inversion layer is at a low altitude of 40 meters ~ 150 meters, and a large amount of smoke is sprayed into it, which makes the smoke accumulate continuously. The atmosphere over London has become a dump for crushed garbage in factories and home chimneys. The data of post-investigation showed that the dust concentration was as high as 4.46μg/L, which was 10 times of the usual level. Sulfur dioxide is as high as 1.34 μ g/L, which is six times as high as usual. Iron trioxide in flue gas promotes the oxidation of sulfur dioxide to produce sulfuric acid foam, which condenses on flue gas to form acid mist.