9.1 stratospheric ozone depletion & 9.2 reducing ozone depletion

Stratospheric ozone & life on earth

Ozone in the stratosphere absorbs UV-C & much of UV-B radiation

-life wouldn’t be possible w/out it

Human health benefits: prevents skin cancer & cataracts

Tropisheric = respiration irritant, damaging to plant tissue & precursor to photochemical smog

How ozone absorbs UV-B & UV-C

UV-C breaks O2 into free oxygen atoms (2O)

-free oxygen combines with O2 molecule → ozone forms

-UV-C reverses rxn (breaks O3 to O2 & O) which can bond with another free O to form O2

-continued formation absorbs all UV-C & much UV-B radiation → protects organisms on earth

Anthropogenic ozone depletion

CFCs (chlorofluorocarbons) are primarily anthropogenic causes of O3 breakdown

-used as refrigerant chemicals and propellants in containers (hairspray)

-caused free chlorine atom to separate from CFCs

Natural ozone depletion

Antarctica spring melt forms polar stratospheric clouds (PSC)

CL atoms due to ozone from CFCs (break O3 down into O2 over & over)

Reducing ozone depletion

Main way to reduce anthropogenic O3 depletion is phasing out & replacing CFCs

-Montreal protocol: global agreement to phase CFCs out in refrigerators, aerosols & other uses