What is the reason for the formation of Antarctic ozone hole?

Ozone in the atmosphere is that ultraviolet rays in sunlight act on oxygen molecules, which decompose into oxygen atoms, and oxygen atoms combine with oxygen molecules to form ozone. Most ozone exists in the stratosphere at the height of 10 ~ 50km, and its maximum density is about 20km. The total content of ozone is less than one tenth of the number of molecules in the earth's atmosphere. If the ozone in the atmosphere is concentrated at sea level, the thickness is only about 3 mm. Sunlight contains an ultraviolet ray, which is recognized as the chief culprit of skin cancer and cataract. Because ozone can absorb ultraviolet rays from the sun, it protects life on earth from extinction. 1985, British Antarctic scientists reported the discovery of an ozone hole over Antarctica. Every year from the end of August to the end of September, the total ozone over the Antarctic continent at a height of 20 kilometers begins to decrease, and the largest hole appears at the beginning of 65438+ 10, covering the entire Antarctic continent and the southern tip of South America. In 165438+ 10, the ozone increases again and the hole disappears. In fact, the so-called ozone hole does not mean that the entire ozone layer has disappeared, but that the ozone content in the atmosphere has decreased to a certain extent. Studies have shown that human activities, especially the extensive use of freon as refrigerant and atomizing agent, are the important reasons for the Antarctic ozone hole. Freon leaked into the atmosphere in human production and life is decomposed into chlorine atoms by ultraviolet rays in the upper atmosphere, and chlorine atoms decompose ozone. At the height of 20 kilometers above the Antarctic, due to the very low temperature, ice crystal clouds are easy to form, which intensifies the catalysis of chlorine and decomposes a lot of ozone. The closed atmospheric circulation system in Antarctica makes the decomposed ozone not replenished. Therefore, chemical reactions and atmospheric movements in the atmosphere complement each other and are closely related, forming an ozone hole over Antarctica.