Erosion of Ozone Layer
Dec 18, 2015
Erosion of Ozone Layer
Erosion of Ozone layer
Position of ozone layer:
Ozone layer is mainly locate at height 20:40Km above sea level in the lower part of
stratosphere layer .
Why? Because it is the first layer of atmospheric envelope which faces ultraviolet radiations emitted from the sun, and also it contains suitable amount of oxygen
gas.
Structure of Ozone layer: Ozone layer is composed of Ozone gas (O3) which consists of three oxygen
atoms .
How? When ultraviolet rays pass from oxygen molecule it break the covalent bond and become one atom then it combine with anther molecule to make (O3)
molecule .
Ultraviolet rays
UV
O2 O + OUV
O + O2 O3
Thickness of Ozone layerThe English scientist
DOBSON postulated that the thickness of the Ozone layer is compressed into 3mm. Only if it were under the normal pressure and 0 C temperature (STP).
The scientists took “DOBSON” as a measuring unit of degree for Ozone layer (100 DOBSON unit (DU) is defined as 1mm. Thickness)
so
The thickness of Ozone layer=300DU.
The importance of
Ozone layer: There are three types of UV rays that differ in wavelength and effect:
Types of UVrays
Near UVRays
(UV-A)
Medium UVRays
(UV-B)
Far UVRays
(UV-C )
Living organisms
Harmful effects
Human: •Increase the rate of skin cancer• cataract
Amphibians: •Spoil eggs
Marine organisms:
•Death of plankton which is the main nutrient of small marine creature.
Terrestrial plants:
•Upset the photosynthesis process
Erosion in September! Since 1978, scientists have noticed
that there was erosion in Ozone layer above the South pole ,and it
increase in September : Why?
Because all pollutants assemble as black cloud and are pushed by wind towards south pole making Ozone depletions increase
from year to year .
Pollutant of Ozone layer: 1. Chlorofluorocarbon (CFC).
2. Methyl bromide gas.3. Halons.4. Nitrogen oxides.
Chlorofluorocarbon (CFC)They are compounds known
as Freon, which used in: - Cooling substance in air condition
sets.- propellant substance in aerosols.- flating substance in making foam
backing.- solvent substance for cleaning
electric circuits slides.
Methyl bromide gas: It is used as an
insecticide to preserve stored agricultural crops.
Halons:They are used in fire extinguishers.
Nitrogen oxides:They are produced from the burning fuel of ultrasound planes (Concord).
The effect of (CFC) compounds on Ozone layer:
CFC compounds erode ozone layer in three steps as the
following :
The first step:CFCl3
UVCFCl2+Cl
The second step:
Cl + O3 O2 + ClO
The third step:
ClO + O3 2O2 + Cl
Protecting the Ozone layer: - An international conference
was held in “CANADA" in
16-09-1987 to discuss how to protect Ozone layer and take all suitable measures
to solve this problem .
-They reached a group recommendations called
“MONTEREAL PROTOCOL” where it is
signed by 191 nations :
•Using of chlorofluorocarbon compounds must be reduced and find safer alternatives.
•Stop producing concord planes as their exhausts effect the Ozone layer.
Some of these recommendations:
In 1990, Montreal Protocol in London has been modified in a way that all nations must ban:
• Production or handing CFC compounds otherwise they will be allowed to export their goods.
Amount of production In 1989 about 1010 m.t
In 1990 about 700 m.tIn 1991 about 600 m.tIn 1992 about 500 m.tIn 1993 about 400 m.tIn 1994 about 200 m.tIn 1995 less than 200 m.tIn 1996 less than 200 m.t
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