200
responsible for the harmful process. Compounds
called freons in ordinary speech were mostly
applied as refrigerating agents, power-gases in
various sprays and foaming material in the plastic
industry. These are very stable compounds in the
troposphere but in the stratosphere they have a
decisive role in disintegrating stratospheric
ozone. Later ozone thinning was also proved
above the Arctic as well (Hofmann et al. 1989)
and it was also revealed that the average concentration of stratospheric ozone decreased in the
entire Earth.
Freons do not disintegrate in the troposphere;
therefore, they get into the stratosphere chemically unchanged. Above the layer with maximum
ozone concentration (at a height of 30 km) without the protection of ozone ultra violet radiation
is very strong. This is able to break a chlorine
atom off the freon (Eq. 4.1). This free chlorine
atom reacts with ozone producing chlorine monoxide and biatomic oxygen molecule (Eq. 4.2).
CFCl
CFCl
radiation
3
2
UV
Cl
+
′
(4.1)
Cl
ClO
′
′
+
→
+
O
O
3
2
(4.2)
ClO
C l
′
′
+
→
+
O
O
3
2
2
(4.3)
ClO
C l
′
′
+ →
+
′
O
O 2
(4.4)
In equation (Eq. 4.3) reacting with chlorine monoxide another ozone molecule is broken and the
obtained chlorine atom can enter reaction
(Eq. 4.2). In reaction (Eq. 4.4) free chlorine is
again produced inducing again reaction (Eq. 4.2).
Ozone breaking effect of chlorine only ceases if
the chlorine atoms reacting with some kind of
other compounds trapped into “chlorine” reservoirs like in the case of equation (Eq. 4.5).
NO
ClNO
2
3
+
→
′
ClO
(4.5)
Chlorine nitrate (ClNO 3 ) absorbs chlorine in stable form that is not able to disintegrate ozone
molecules. Such reservoir could be hydrochloric
acid as well formed by free chlorine reacting
with methane. Although nitrogen monoxide is not
chlorine reservoir but it contributes to the regeneration of ozone (Eq. 4.8) with attracting the oxygen atom of chlorine monoxide (Eq. 4.6) and the
produced nitrogen dioxide absorbs visible light
(Eq. 4.7) producing oxygen atoms to this effect.
NO
NO
+
→
+
′
ClO
C l
2
(4.6)
NO
NO O
visible light
2
+ ′
(4.7)
′ +
→
O O
O
2
3
(4.8)
Experts researching ozone destruction presume
that specific climatic conditions weakening reactions (Eqs. 4.5–4.8) regularly return above the
Antarctic thus reactions (Eqs. 4.1–4.4) become
dominant, i.e. more ozone is disintegrated
(Stolarski 1988, 2001).
A simplified outline of the process is given in
Fig. 4.91. Apart from the already discussed features a hypothesis was created that considers that
polar stratospheric clouds could help the disintegration of chlorine reservoirs, setting free chlorine in this way that reacts with ozone when
temperature rise and the process of ozone decomposition starts again (Crutzen and Arnold 1986).
Crutzen PJ, Molina MJ and Rowland SF
received Nobel Prize for exposing the process of
ozone disintegration in 1995 (over 20 years after
publishing their results). The scientists pointed
out that CFCs have very long life-cycle in the
atmosphere; therefore, even if their production
and application is stopped ozone depletion in the
stratosphere will continue for decades.
From the 1980s even politicians were concerned regarding the hindrance of the destruction
of the ozone shield recognising the danger of
ozone depletion and the acceleration of the process (Fig. 4.92).
Frameworks were provided for the protection
of the ozone layer in a UN convention accepted
in Vienna in 1985. Although only principles were
framed in the convention but it did not take long
for particular measures to come. Montreal
Protocol was created in 1987 that contained regulations related to five Freon and three halon
gases. Only 24 (mostly developed) states signed
the protocol at that time but the effect of the protocol was expanded several times for various
ozone damaging materials and deadlines to ban
their production and application grew shorter.
The number of countries joining the protocol
4 Changes on Earth as a Result of Interaction Between the Society and Nature
responsible for the harmful process. Compounds
called freons in ordinary speech were mostly
applied as refrigerating agents, power-gases in
various sprays and foaming material in the plastic
industry. These are very stable compounds in the
troposphere but in the stratosphere they have a
decisive role in disintegrating stratospheric
ozone. Later ozone thinning was also proved
above the Arctic as well (Hofmann et al. 1989)
and it was also revealed that the average concentration of stratospheric ozone decreased in the
entire Earth.
Freons do not disintegrate in the troposphere;
therefore, they get into the stratosphere chemically unchanged. Above the layer with maximum
ozone concentration (at a height of 30 km) without the protection of ozone ultra violet radiation
is very strong. This is able to break a chlorine
atom off the freon (Eq. 4.1). This free chlorine
atom reacts with ozone producing chlorine monoxide and biatomic oxygen molecule (Eq. 4.2).
CFCl
CFCl
radiation
3
2
UV
Cl
+
′
(4.1)
Cl
ClO
′
′
+
→
+
O
O
3
2
(4.2)
ClO
C l
′
′
+
→
+
O
O
3
2
2
(4.3)
ClO
C l
′
′
+ →
+
′
O
O 2
(4.4)
In equation (Eq. 4.3) reacting with chlorine monoxide another ozone molecule is broken and the
obtained chlorine atom can enter reaction
(Eq. 4.2). In reaction (Eq. 4.4) free chlorine is
again produced inducing again reaction (Eq. 4.2).
Ozone breaking effect of chlorine only ceases if
the chlorine atoms reacting with some kind of
other compounds trapped into “chlorine” reservoirs like in the case of equation (Eq. 4.5).
NO
ClNO
2
3
+
→
′
ClO
(4.5)
Chlorine nitrate (ClNO 3 ) absorbs chlorine in stable form that is not able to disintegrate ozone
molecules. Such reservoir could be hydrochloric
acid as well formed by free chlorine reacting
with methane. Although nitrogen monoxide is not
chlorine reservoir but it contributes to the regeneration of ozone (Eq. 4.8) with attracting the oxygen atom of chlorine monoxide (Eq. 4.6) and the
produced nitrogen dioxide absorbs visible light
(Eq. 4.7) producing oxygen atoms to this effect.
NO
NO
+
→
+
′
ClO
C l
2
(4.6)
NO
NO O
visible light
2
+ ′
(4.7)
′ +
→
O O
O
2
3
(4.8)
Experts researching ozone destruction presume
that specific climatic conditions weakening reactions (Eqs. 4.5–4.8) regularly return above the
Antarctic thus reactions (Eqs. 4.1–4.4) become
dominant, i.e. more ozone is disintegrated
(Stolarski 1988, 2001).
A simplified outline of the process is given in
Fig. 4.91. Apart from the already discussed features a hypothesis was created that considers that
polar stratospheric clouds could help the disintegration of chlorine reservoirs, setting free chlorine in this way that reacts with ozone when
temperature rise and the process of ozone decomposition starts again (Crutzen and Arnold 1986).
Crutzen PJ, Molina MJ and Rowland SF
received Nobel Prize for exposing the process of
ozone disintegration in 1995 (over 20 years after
publishing their results). The scientists pointed
out that CFCs have very long life-cycle in the
atmosphere; therefore, even if their production
and application is stopped ozone depletion in the
stratosphere will continue for decades.
From the 1980s even politicians were concerned regarding the hindrance of the destruction
of the ozone shield recognising the danger of
ozone depletion and the acceleration of the process (Fig. 4.92).
Frameworks were provided for the protection
of the ozone layer in a UN convention accepted
in Vienna in 1985. Although only principles were
framed in the convention but it did not take long
for particular measures to come. Montreal
Protocol was created in 1987 that contained regulations related to five Freon and three halon
gases. Only 24 (mostly developed) states signed
the protocol at that time but the effect of the protocol was expanded several times for various
ozone damaging materials and deadlines to ban
their production and application grew shorter.
The number of countries joining the protocol
4 Changes on Earth as a Result of Interaction Between the Society and Nature