1. Polar Ozone HolesPolar Ozone Holes
 What are Polar ozone Holes ?What are Polar ozone Holes ?
 How does it occur ?How does it occur ?
 How does it work ?How does it work ?

2. What are Polar ozone Holes?What are Polar ozone Holes?
 It’s an area or holes of the Antarctic stratosphere created by theIt’s an area or holes of the Antarctic stratosphere created by the
lack of Olack of O33..
 Scientist noticed that in theScientist noticed that in the mid-1980smid-1980s, depleting the, depleting the
stratospheric ozone over Antarctica by as much asstratospheric ozone over Antarctica by as much as 50 percent50 percent..
 Studies have shown that ozone levels in this region haveStudies have shown that ozone levels in this region have
declined betweendeclined between 4 and 8 percent4 and 8 percent in the past decadein the past decade

3. What are Polar ozone Holes?What are Polar ozone Holes?

4. How does it occur?How does it occur?
A stream of air “polar vortex” circles Antarctica in winter. AirA stream of air “polar vortex” circles Antarctica in winter. Air
trapped within this vortex making the air to be extremely cold.trapped within this vortex making the air to be extremely cold.
This leads to the formation of ice particles known as polarThis leads to the formation of ice particles known as polar
stratospheric clouds (PSCs).stratospheric clouds (PSCs).

5. How does it work?How does it work?
 Acting as catalyst, these PSCs provide a surface for reactionsActing as catalyst, these PSCs provide a surface for reactions
converting HCL, and ClONO2 to more reactive chlorine moleculesconverting HCL, and ClONO2 to more reactive chlorine molecules
(in winter).(in winter).
 Sunlight splits molecular chlorine into chlorine atoms (in earlySunlight splits molecular chlorine into chlorine atoms (in early
spring).spring).
season winter early spring
reaction HCL +ClONO2 Cl2 +HNO3 Cl2 +hv 2Cl

6. How does it work?How does it work?
 Acting as catalyst, these PSCs provide a surface for reactionsActing as catalyst, these PSCs provide a surface for reactions
converting HCL, and ClONO2 to more reactive chlorine moleculesconverting HCL, and ClONO2 to more reactive chlorine molecules
(in winter).(in winter).
 Sunlight splits molecular chlorine into chlorine atoms (in earlySunlight splits molecular chlorine into chlorine atoms (in early
spring).spring).
season winter early spring
reaction HCL +ClONO2 Cl2 +HNO3 Cl2 +hv 2Cl