Ozone depletion describes two distinct,but related observations: a slow,steady decline of about 4 percent per decade in the total amount of ozone in Earths stratosphere since around 1980; and a much larger, but seasonal, decrease in statospheric ozone over Earths polar regions during the same period. The latter phenomenon is commonly referred to as the ozone hole.
In addition to this well-known stratospheric ozone depletion, there are also tropospheric ozone depletion events, whic occur near the surface in polar regions during spring.
The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the most important process in both trends is catalytic destruction of ozone by atomic chlorine and bromine. The main source of these halogen atoms in the stratosphere is photodissociation of chlorofluorocarbon (CFC) compounds, commonly called freons, and of bromofluorocarbon compounds known as halons. These compounds are transported into the stratosphere after being emitted at the surface. Both ozone depletion mechanisms strengthened as emissions of CFCs and halons increased.
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臭氧層消耗說明了想種不同但卻有關聯的結論: 自從1980每十年大約地球的平流層的濃度已全量的4%緩慢,漸進的降低; 但在同時期以季節性的,地球兩級地區的平流層臭氧濃度下降更是巨大,而這個現象也通常被稱為臭氧破洞.
兩極臭氧破洞的產生機制是和中緯度的不同,但最重要的過程在兩個地區的走向是氯與溴對臭氧的催化毀滅作用.而這些在平流程鹵素元素的來源在於氟氯碳化物( 氟利昂)和全鹵化碳氫化合物(海龍)的光和分離作用.這些化合物是在地球表面散發後再傳送到平流層的. 增加氟氯碳化物和海龍的散也同時發增強兩種臭氧減少的機制Source(s): 自己