Worksheet
No.____a
Higher atmosphere (stratosphere)
class
dynamics
name
date
Transport, decomposition and effect of CFCs in the stratosphere
T1 In Figure 1 you can see the Chapman-cycle of the ozone equilibrium and the chlorine-catalysis-cycle
(CCC) depicted as a series of reaction steps and as a reaction cycle. The bold typed reaction arrows
indicate that these elemental processes take place more often than the others (chain reaction).
Add the missing formulas into the four squares of the right part of Fig. 1 and fill into the empty oval
shape the name of the reaction process.
Chapman - Cycle
stratospheric ozone-sink due to CFC
(chlorine-catalysis-cycle)
Figure 1: Chapman-cycle and chlorine-catalysis-cycle of stratospheric chemistry (-Q: dissipation of heat)
T2
The CCC and the Chapman-cycle, that describes the “natural” equilibrium of ozone in the
stratosphere, are linked to each other.
Mark the places where this linkage occurs in the reaction cycle from Fig.1 in red. Mark the same
places also in the box with the Chapman-cycle.
T3
Add the scheme of the cycle in Fig. 1 by showing the function of nitrogen dioxide as "preserving
agent" for the chlorine oxide radicals.
© 2003 ESPERE-ENC / Seesing, Tausch, Universität-Duisburg-Essen; Duisburg
Worksheet
No.____b
Higher atmosphere (stratosphere)
class
dynamics
name
date
Transport, decomposition and effect of CFCs in the stratosphere
You have learned about the effect of CFCs on ozone. The chlorine catalysis cycle takes place some thousand
times before the chlorine radicals react
in another way or before they are
transported out of the ozone layer. But
how do the chlorine radicals, that for
the greatest part originate from the
CFCs, reach the ozone?
T4
Draw the main air flows
of the stratosphere in
Figure 2 and name them.
T5
Mark the place in the
tropopause line where
there seems to be the
smallest difference in
temperature and where
an exchange of matter
seems most probable.
T6
Write a reaction scheme
of the photolysis of CFC
(take F2CCl2 from Fig. 1
as an example) at the
place in Fig. 2 where the
reaction is most likely to
take place.
T7
Now draw the imagined
path of chlorine from the
CFC (taking F2CCl2 as an
example) to the place
where the chlorinecatalysis takes place.
Figure 2: Layers of the atmosphere from the equator to the north
pole (T: tropopause; K: area of the stratosphere with high
concentration of ozone (>16 DU / km)
T8
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Here are some statements on the CFC problem, on transport processes and on ozone. Mark the
right statements with a cross.
The lifetime of CFCs is very long. It is long enough for the CFCs to move to the stratosphere even
though the transfer is extremely slow.
The lifetime of CFCs is not very long, but the transport processes in the atmosphere are fast enough
so the CFCs split after having reached the stratosphere.
Chlorine radicals directly split ozone. A product is formed which reacts with a reactant which is
necessary for the formation of ozone. Therefore the new formation of ozone is hindered.
In the stratosphere many chlorine radicals are formed which then form stable compounds with
ozone. Thus it becomes ineffective as UV-filter.
Since chlorine radicals catalyse the depletion of ozone only small quantities of CFC are necessary for
a considerable depletion of ozone.
The catalytic depletion of ozone and the transport processes alone are not the only factors needed to
explain the seasonal fluctuation of the ozone concentration in the atmosphere (ozone hole).
© 2003 ESPERE-ENC / Seesing, Tausch, Universität-Duisburg-Essen; Duisburg