1974 Sherwood Rowland & Mario Molina Calculated that CFCs were lowering the average concentration of...
22
1974 Sherwood Rowland & Mario Molina Calculated that CFCs were lowering the average concentration of Ozone in the stratosphere. Chemical Time Bomb: Spray cans Leaky refrigeration and air conditioning equipment Production and burning of foam plastics CFC 11 - CCL 3 F CFC 12 - CCL 2 F 2 trichlorofluoromet hane dichlorofluorometh ane Take 10 - 20 years to reach the stratosphere Turbulent atmospheric mixing Transport on aerosols 1
-
Upload
mark-fields -
Category
Documents
-
view
222 -
download
0
Transcript of 1974 Sherwood Rowland & Mario Molina Calculated that CFCs were lowering the average concentration of...
1974Sherwood Rowland & Mario MolinaCalculated that CFCs were lowering
the average concentration of Ozone in the stratosphere.
Chemical Time Bomb: Spray
cansLeaky refrigeration and air conditioning equipmentProduction and burning of foam plastics
CFC 11 - CCL 3FCFC 12 - CCL2F2
trichlorofluoromethanedichlorofluoromethane
Take 10 - 20 years to reach the stratosphereTurbulent atmospheric
mixingTransport on aerosols
1
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
OO33
As a secondary air As a secondary air pollutant in the pollutant in the troposphere, ozone forms troposphere, ozone forms as part of photochemical as part of photochemical smog.smog.
In the lower In the lower stratospherestratosphere, the , the formation formation andand breakdown of breakdown of ozone ozone absorbs UVabsorbs UV radiation. radiation. This is vital to all life on This is vital to all life on EarthEarth..
OzoneOzone:: Is an unstable Is an unstable
reactive oxidizerreactive oxidizerIs a health threat to Is a health threat to elderly and youngelderly and youngContributes to forest Contributes to forest decline.decline. Reduces crop yieldReduces crop yield
Oxidizes stable organics Oxidizes stable organics (plastic, rubber)(plastic, rubber) Is a highly efficient Is a highly efficient greenhouse gasgreenhouse gas
Ozone damage Ozone damage to potato to potato plants.plants.
2
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
Earth’s atmosphere is layered with each layer having its own characteristic composition, density and temperature ranges.
This presentation will focus on the Ozone concentrated in the lower stratosphere at 18000 to 20000 meters.
Thermosphere
Mesosphere
Stratosphere
Troposphere
Mesopause
Stratopause
Tropopause
3
Ozone data source :
http://www.awi.de/en/infrastructure/stations/neumayer_station/observatories/meteorological_observatory/upper_air_soundings/ozone_soundings/
From this page, use their search function.
Type in Ozone Soundings
The Alfred Wegener Institute conducts many types of atmospheric and oceanographic research. Ozone monitoring is only one. You will also find links to Arctic research as well
4
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
2004 Antarctic ozone profile.
stratosphere
15
67
83
92
105
120 14
9170
213
235 243 25
2
262 27
0
287 29
6 306
313 32
1
330
344
353
1
140
140
140 140
140
120
140
140
120
100
80
60 40
20
20
40
80 60 80
100 12
0 140
145
5
Day O3 1 14515 140
67 140
83 140 120 120
92 140 149 140
170 140
213 120
235 100
243 80
252 60
262 40
270 20
287 20
296 40
306 80
313 60
321 80
330 100
344 120
353 140
2004 Ozone profile data
1501401301201101009080706050403020100Ozone40036032028024020016012080400DayDay6 Sept16 Oct
O3 concentration in nanobars
6
QuickTime™ and a decompressor
are needed to see this picture.
7
2012
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
pp O3 nb
360340320300280260240220200180160140120100806040200Day
Day
2012 Antarctic Ozone profile
O3 concentration in nanobars
8
6 Sept
16 Oct
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
2012
2004
9
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
10
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
Ant 87
18000 m Ozone concentration 1987 Antarctic
220
360
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Ant 87
Ant 97
18000 m Antarctic Ozone 19871997
16 Oct6 Sept
O3 concentration in nanobars
11
18000 m Antarctic Ozone
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Ant 87
Ant 97
Ant 06
198719972006
6 Sept
16 Oct
O3 concentration in nanobars
12
180175170165160155150145140135130125120115110105100959085807570656055504540353025201510
50
Ant 97
Ant 06
Ant 12
6 Sept
16 Oct
Austral winter Ozone depletion. 18000m profile
O3 concentration in nanobars
13
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
14
2006 Arctic Ozone data
ozoneconcentration125185175180135130130120120115115115120130140130125
day1315990120151181212227243258273288304319334365
Date1/11/312/283/314/305/316/307/318/158/309/159/3010/1511/111/1511/3012/31
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
o
z
o
n
e
40036032028024020016012080400
day
day
Arctic Ozone 20,000 m profile 2006
21 March 6 Sept
16 Oct
15
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
o
z
o
n
e
40036032028024020016012080400
day
day
Arctic Ozone 20,000 m profile 2006
18000 m Antarctic Ozone
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Ant 87
Ant 97
Ant 06
19871997200616
Lower
depletion : Warmer temperatures
Weaker polar vortex
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
O2 + uv ------------> 2 O
2O + 2 O2 ---------> 2O3
2O3 + uv ------> 3O2
Both processes absorb ultraviolet radiation (UVB)
17In the lower Stratosphere the formationand breakdown of O3is a natural ongoing process
Once Earth’s atmosphere began to be enriched with oxygen, beginning about 2.2 billion years ago during the Early Proterozoic, the stage was set for the eventual emergence of life on to the land.
18
Factors contributing to Ozone DepletionHalogenated hydrocarbons
Chlorofluorocarbons---- CFC’sMethyl Bromide ----Soil
fumigantsFire fighting compound
Biomass burning
Volcanic eruptions
Volatile cleaning compounds
Carbon tetra chloride
Trichloroethane
How these heavy molecules get to the stratosphere.
Antarctica
Antarctic winter:
Extremely cold air isolated over AntarcticaPolar Stratospheric Clouds transport HH on
ice crystals
Warmer air circulating with the West Wind Drift.
Antarctic Polar Vortex
S. America
Through the mixing which occurs between global convection cells, these compounds are transported to high latitudes.
19
What happens.
Chlorofluorocarbons and methyl bromideCCl2F
2
CH3Br
With the onset of the Austral spring and the return of sunlight to the Antarctic region, simplified reactions result in the breakdown of ozone in the lower stratosphere over Antarctica.
CCl2F2 + uv ---------> CClF2 + ClCl + O3 ---------> ClO + O2
The halogen acts as a catalyst in the destruction of Ozone without the benefit of UV absorption.
The residence time for these halogens can be 50 - 100 years.
Cl and Br are the primary destructive halogens
20
CLO + O3 ----------> Cl + 2O2
http://www.atm.ch.cam.ac.uk/tour/part3.html
This is a simplified illustration. The link below has the complex chemistry
http://ozonewatch.gsfc.nasa.gov
QuickTime™ and a decompressor
are needed to see this picture.
NASA provides global ozone images.
21
22Units used in Ozone measurement.
Nanobars ( nb ) = .000001 millibarsMillipascals ( mPa ) = .00001 millibars1.0 mPa = 10
Nb14 mPa = 140 nb Conversion necessary to compare Arctic and Antarctic ozone pressure
Dobson unit DU
Used on ozone mapping images from NASA
A Dobson unit (DU) would produce a layer of gas .01mm thick at STP. ie. 300DU = a layer 3.0mm thick
1 DU is equivalent to about .8 nb
