Botkin Environmental Science Earth as Living Planet 8th txtbk

482 CHAPTER 21 Air Pollution
-
-
2 -
-
-
-
-
-
Measuring Stratospheric Ozone
3
-
-
-
-
O 3 is produced by
photodissociation of O 2
by UVC from the sun.
O then combines with O 2
to produce O 3 .
O 3 is destroyed by
catalytic chain reaction
of ClO. Similar reactions
occur with NO x and BrO x .
Net result
FIGURE 21.15 Processes of
natural formation of ozone and
destruction by CFCs, N 2 O, and
methyl bromide. (Source: Modified
from NASA-GSFC, “Stratospheric
Ozone,” accessed August 22, 2000,
at http://see.gsfc.nasa.gov.)
Sun
O 2
O + O 2
O 3
Cl + O 3
ClO + O
ClO + O 2
Cl + O 2
O + O 3
2O 2
O
Ozone is
destroyed
NO x
ClO x
BrO x
Stratosphere
Troposphere
N 2 O
CFCs
Emissions
from Earth
Methyl
bromide
Catalytic agents are
produced from long-lived
source gases, released
into the troposphere,
and transported to the
stratosphere