Energie und Umwelt IER - Universität Stuttgart und Umwelt Prof. Dr.-Ing. Rainer Friedrich IER...
-
Upload
duongnguyet -
Category
Documents
-
view
213 -
download
1
Transcript of Energie und Umwelt IER - Universität Stuttgart und Umwelt Prof. Dr.-Ing. Rainer Friedrich IER...
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Reduzierung der Ozonkonzentration in der Stratosphäre (‘Ozonloch’)
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Troposphärischer (2, 4, 6 und 8 km Höhe) und stratosphärischer (20, 22, 24 km Höhe) Ozontrend 1976-1990 am Hohenpeissenberg bei
München
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Spektrale Energieverteilung der Sonnenstrahlen1.Ausstrahlung einer Oberfläche mit 6000 K (Sonne)2.Sonnenstrahlung außerhalb der Atmosphäre (extraterrestrisch) 3.Sonnenstrahlung unterhalb der Ozonschicht 4.Sonnenstrahlung an der Erdoberfläche unter einer wasserdampffreien Atmosphäre 5.dasselbe mit durchschnittlicher Wasserdampfabsorption
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
O2 + hν (λ<242 nm) 2 O2 [ O + O2 O3 ]
-----------------------------3 O2 2 O3
Ozone Production in the Stratosphere
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
The role of CFC´s
Cl + O3 ClO + O2
O3 + hν O + O2
ClO + O Cl + O2---------------------
2 O3 + hν 3 O2
1) Production of chloro-radicals: CFCl3 + hν CFCl2 + Cl
2 Cl + 2 O3 2 ClO + 2 O2
ClO +ClO + M Cl2O2 + M
Cl2O2 + hν 2 Cl + O2---------------------
2 O3 + hν 3 O2
2) Destruction processes of ozone:
However, due to quenching processes using NO2, ClO is removed from the processes above:
HO + NO2 + M HNO3 + M
ClO + NO2 +M ClONO2 + M
⇒Thus the ozone concentration remains relatively high
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
The ozone hole - The role of CFC´s
Cl + O3 ClO + O2
O3 + hν O + O2
ClO + O Cl + O2---------------------
2 O3 + hν 3 O2
1) Production of chloro-radicals: CFCl3 + hν CFCl2 + Cl
2 Cl + 2 O3 2 ClO + 2 O2
ClO +ClO + M Cl2O2 + M
Cl2O2 + hν 2 Cl + O2---------------------
2 O3 + hν 3 O2
2) Destruction processes of ozone:
Quenching processes:
HO + NO2 + M HNO3 + M
ClO + NO2 +M ClONO2 + M
⇒Radical reservoirs
Photolysis of the quenchingproducts
HNO3 + hν OH + NO2
ClONO2 + hν ClO + NO2
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
The ‘ozone hole’ = reduction of concentration of ozone above the Antarctic in September and October
During the polar winter (no solar radiation, < - 80° C) polar stratospheric clouds (PSC) with frozen water and HNO3molecules are formed
e.g. by the following reaction that is fast on ice surfaces: ClONO2 + HCl Cl2↑ + HNO3 (ice)
-> as soon as sunlight is available (end of Sept.), photo dissociation of Cl2 starts: Cl2 + hν 2 Cl .
-> However NO2 ( reaction HNO3 + hν OH + NO2 ) is not yet formed, as HNO3 is still hold in ice -> no quenching reaction
-> ozone is destroyed.
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Chlorofluorocarbons CFCs
- Developed in 1928 by Thomas Midgley as refrigerants
- Stable, non-flammable, non-toxic chemicals- Physical properties ideal for many uses such as
aerosols, refrigeration, air-conditioning, blowing agents for foam packaging and insulation, solvents, dry-cleaning, etc.
- Rapid growth in sales from the 1940s onwards until ..
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
CFC-11 CClF3CFC-12 CCl2F2CFC-113 CCl3CF3CFC-114 CCl2FCF3CFC-115 CClF2CF3
HCFC-22 CHClF2 HFC-32 CH2F2HCFC-123 CHCl2CF3 HFC-125 CHF2CF3HCFC-124 CHClF2CF3 HFC-134a CH2FCF3HCFC-141b CH3CCl2F HFC-143a CH3CF3HCFC-142b CH3CClF2 HFC-152a CH3CHF2HCFC-225ca CHCl2CF2CF3 HFC-227ea CF3CHFCF3HCFC-225cb CHClFCF2CClF2 HFC-236fa CF3CH2CF3
HFC-245fa CF3CH2CHF2HFC-245ca CHF2CF2CH2FHFC-245eb CF3CHFCH2FHFC-365mfc CF3CH2CF2CH3
Chlorofluorocarbon (CFCs)
Fluorocarbon Alternatives to CFCs
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
CFC Production – total by 1972 over 5 Mio t
0
50.000
100.000
150.000
200.000
250.000
300.000
350.000
400.000
1931
1935
1939
1943
1947
1951
1955
1959
1963
1967
1971
CFC-11CFC-12
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Chlorofluorocarbons CFCs
- 1972 CMA Fluorocarbon Program Panel set up to look at „the effect (if any) of CFCs on the atmosphere“
- Atmospheric measurements found traces of CFCs in „clean air“
- 1974 Rowland and Molina hypothesis: CFCs broken down by UV in the stratosphere. Cl atoms enter into a catalytic cycle that breaks down ozone
- 1980s US aerosol ban, European production cap- First signs of Antarctic Ozone Hole - 1987 Montreal Protocol
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
CFC Production to 1988
0 50.000
100.000 150.000 200.000 250.000 300.000 350.000 400.000 450.000 500.000
1931
1936
1941
1946
1951
1956
1961
1966
1971
1976
1981
1986
CFC-11CFC-12
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Fluorocarbon alternatives to CFCs
- Hydrochlorofluorocarbons (HCFCs) and Hydrofluorocarbons (HFCs) developed from the mid-1970s onwards
- Unprecedented amount of environmental testing- Less than 25% take up as alternatives to CFCs- Mostly in refrigeration, air-conditioning and foam-
blowing- Aerosol and solvent markets went almost entirely
over to non-fluorocarbon alternatives: hydrocarbons, ammonia, water, alternative technologies
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
International Regulations on Fluorocarbons
- 1987 UN Montreal Protocol and later amendments
- Regulate consumption of CFCs and HCFCs- 1992 UN Framework Convention on Climate
Change (UNFCCC) adopted at Earth Summit in Rio
- 1997 Kyoto Protocol negotiated as amendment to UNFCCC – came into force in 2005
- Aims to reduce emissions of CO2 and five other greenhouse gases: CH4, N20, PFCs, SF6 and HFCs
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
Montreal Protocol
- Developed countries phase out CFCs, methylchloroform, carbon tetrachloride by 1996
- Can produce CFCs up to 15% of 1986 baseline for developing countries and own essential uses
- Freeze HCFC production in 1996; phase out by2030
- Developing countries can produce and purchaseCFCs and carbon tetrachloride until 2010 and methyl chloroform until 2015
- Freeze HCFC consumption in 2015, phase out by 2040
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
CFC phase out-schedule in developed countries
1987 1990 1992 1990 1994
Original Montreal Protocol
London Montreal Protocol
Copenhagen Montreal Protocol
U.S. Clean Air Act
Amendments
European Community Schedule
1990 100%1991 100% 100% 85%1992 100% 100% 80%1993 80% 80% 75% 50%1994 80% 80% 25% 25% 15%1995 80% 50% 25% 25% 0%1996 80% 50% 0% 0%1997 80% 15%1998 80% 15%1999 50% 15%2000 50% 0%
Energie und UmweltProf. Dr.-Ing. Rainer Friedrich
IER
0
50.000
100.000
150.000
200.000
250.000
300.000
350.000
400.000
450.000
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Met
ric T
ons
(10^
3 kg
)
CFC-11
CFC-12
CFC-113
CFC-114
CFC-115
HCFC-22
HCFC-124
HCFC141bHCFC142b
HFC-134a
HFC-125
HFC-143a
Fluorocarbon production data reported to AFEAS (2005)