Abnormal low temperature occurred in London 10 and early February 1952, 1 16438. Residents burned a lot of coal at home to keep warm, and soot was discharged from the chimney. If smoke diffuses in the atmosphere, it will not gather to produce dense fog. But at that time, there was an anticyclone over London, which warmed the air over London and caused the temperature in high places to be higher than that in low places. In this way, the air in London can't rise, so it stays in London and leaves soot in London. Smoke and waste gas are constantly discharged from citizens' homes and factories, so more and more pollutants are gathered in the air in London. At the same time, the water vapor content in the air was very high. In cold air, water vapor is cooled to the dew point, and a large amount of smoke provides condensation nuclei for them, so thick smoke appears.

In this incident, London discharged 1000 tons of smoke and dust, 2,000 tons of carbon dioxide, 140 tons of hydrogen chloride (the main component of hydrochloric acid), 14 tons of fluoride, and the most terrible-370 tons of sulfur dioxide, which was subsequently converted into 800 tons of sulfuric acid (.

According to some experts' statistics, this smog caused about 4,000 deaths in 1952 and 65438+February, and there was a follow-up effect-it caused about 8,000 deaths in 1953 and 65438+ 10 and February. However, some analysts said that the increase in the death rate at the beginning of 1953 should be attributed to the flu, which has always been supported by the British government.

Los Angeles photochemical smog

In the 1940s, there were 2.5 million cars in Los Angeles, which consumed about11000 tons of gasoline and emitted more than1000 tons of hydrocarbons (CxHy? Or RC), more than 300 tons of nitrogen oxides (nitrogen oxides), 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. Los Angeles is surrounded by mountains on three sides, and atmospheric pollutants are not easy to spread, and Los Angeles is often affected by inversion, which makes pollutants gather in Los Angeles. 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.

1955 In September, due to air pollution and high temperature, more than 400 elderly people over 65 died in just two days, and many people suffered from eye pain, headache, dyspnea and even death.