Antarctica ozone hole formation over

Figure 12.17 shows the ozone profiles over the U.S. Amundsen-Scott Station at the South Pole in 1993 on August 23 prior to formation of the ozone hole and on October 12 after the ozone hole had developed. The total column ozone decreased from 276 DU on August 23 to only 91 DU on October 12, and, in addition, there was essentially no ozone in the region from 14 to 19 km (Hofmann et al., 1994a). During the same period at the McMurdo Station in Antarctica, the total column ozone decreased from 275 to 130 DU (B. J. Johnson et al., 1995). While similar profiles have been observed since the discovery of the ozone hole, these data show some of the most extensive ozone destruction ever observed, although 1994 and 1995 showed almost as much 03... 

O Reading Check Explain what triggers the formation of the ozone hole over Antarctica. 

In the mid-1980s, evidence began to accumulate that an Antarctic ozone hole developed in late winter, depleting the stratospheric ozone over Antarctica by as much as 50 percent (Figure 17.8). In the stratosphere, a stream of air known as the polar vortex circles Antarctica in winter. Air trapped within this vortex becomes extremely cold during the polar night. This condition leads to the formation of ice particles... 

Chlorine peroxide ClOOCl is formed by the termolecular recombination reaction of CIO radicals when the concentration of CIO radicals is high. Among the reservoir molecules in the stratosphere over the Antarctica in wintertime, ClOOCl has the highest concentration, and its photolysis in springtime is very important for the formation of the ozone hole. 

Research has shown that heterogeneous catalysis is most likely responsible for the annual formation of an ozone hole over Antarctica. After the discovery of the Antarctic ozone hole in 1985, scientists wondered why there was such a dramatic drop in ozone over Antarctica but not over the rest of the planet. After aU, the chlorine from chlorofluorocar-bons that catalyzes ozone destruction is evenly distributed throughout the entire atmosphere. 

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