APES Unit 9 Ozone Notes

ozone layer

-ozone layer in the stratosphere protects life on Earth from harmful UV radiation.

-general ozone depletion and a "hole" over Antarctica are of great concern.

-this "hole" forms during October (Antarctic spring).

CFCs

-chlorofluorocarbon

-react with UV radiation and ozone.

-these reactions pull oxygen atoms away from the ozone molecules.

-ozone levels decrease

montreal protocol

was an international agreement to reduce the production and use of CFC's (1st) and HCFC's (2nd)

-included the phasing out of halons, which are used in fire extinguishers.

-halons contain Br (bromine), which has greater potential for ozone destruction that chlorine.

ozone recovery

-HCFC's have replaced CFC's, but HCFC's still contain chlorine.

-an alternative to HCFC's are HFC's.

-HFC's do not contain chlorine so they wouldn't damage ozone.

-However HFC's can contribute to global warming.

-HFO's are even better and have little global warming potential.

3 kinds of UV radiation

UVA- never absorbed by ozone

UVB- sometimes absorbed by ozone

UVC- always absorbed by ozone

why is more UV a concern

-increases premature aging and skin cancers (especially melanoma, the most deadly!)

-increases the development of cataracts (clouding of the lens that affects vision).

-suppresses immune system.

-can damage crops, reducing crop yields.

-can destroy phytoplankton, which reduces higher trophic level fish yields