evaluation of co and sf 6 as quantitative tracers for fossil fuel co 2 : the experimentalists’...
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Evaluation of CO and SF6 as quantitative tracers for fossil fuel
CO2:
The Experimentalists’ view
Ingeborg Levin1, Ute Karstens2, Ulrike Gamnitzer1,Christoph Schönherr1, Bernd Kromer1
and Samuel Hammer1
1Institut für Umweltphysik Universität Heidelberg
2Max-Planck-Institut für Biogeochemie, Jena
February CO2 Fluxes
Fossil fuel CO2
(EDGAR V3.2 FT, Olivier et al., 2005)
Biome-BGC NEE (Churkina et al., 2003)
10-9 kg C m-2 s-10 10 20 30 40 50-10
Heidelberg: February 2002 (REgional MOdel)
Heidelberg: June 2002 (REgional MOdel)
Schauinsland: February 2002 (REgional MOdel)
Can we validate these model results ?
… measure total CO2 and
fossil fuel CO2
—› measure Radiocarbon (14C) in atmospheric CO2 …
… because fossil fuel CO2 contains no 14C and dilutes
atmospheric 14CO2
Long-term 14CO2 background observations in Europe
„clean“ 14CO2
background level in the Alps
Reference: Atmosphere in 1890
0
200
400
600
800
1000
1950 1960 1970 1980 1990 2000
14CO2 Vermunt
14CO2 Jungfraujoch
14C tree rings [Stuiver and Quay, 1981]
14C
[‰]
1985 1990 1995 2000 20050
50
100
150
200
continental reference Schauinsland monthly means Heidelberg monthly means
14
C [‰
]
Long-term 14CO2 observations in Europe
„clean“ 14CO2
background level in the Alps
Depletion of the 14CO2 level close to fossil fuel sources
Monthly mean fossil fuel CO2 at Schauinsland station and in
Heidelberg
mean fossil fuel CO2 offset:
Schauinsland:ca. 1.4 ppm
Heidelberg:ca. 10 ppm
0
50
100
150
200
continental reference Schauinsland monthly means Heidelberg monthly means
1
4C
[‰]
0
5
10Schauinsland
1985 1990 1995 2000 20050
20
40 total offset fossil fuel offset
Heidelberg
foss
il fu
el C
O2 [p
pm
]
… but the temporal resolution of our 14C measurements is poor:
weekly means
… and the sensitivity is quite low:
minimum uncertainty
≈ ±2.5 ‰ of 370 ppm ≥ ±1 ppm
—›proxies/surrogates needed
to substitute 14CO2 observations
Carbon Monoxide (CO)
Sulfur Hexafluoride (SF6)
29.09.2004 01.10.2004 03.10.20040
15
30
SF
6 [p
pt] 1.4 ppm
0
300
600
CO
[ppb
]
350
400
450
29.09.2004 01.10.2004 03.10.2004
CO
2 [p
pm]
Continuous trace gas observations in Heidelberg in October 2004
CO2
CO
SF6
CO: Mainly anthropogenic sources (fossil fuel burning) and oxidation of hydrocarbons
chemical life time ca. 2 months
SF6: Only anthropogenic sources roughly distributed according to population density
chemically inert
14CO2, fossil fuel CO2 and CO offset in Heidelberg
2001 2002 2003 20040
20406080
100120
2001 2002 2003 20040
200
400
Jungfraujoch (background)
14C
[‰]
Heidelberg
2001 2002 2003 20040
10
20
30fossil fuel CO
2
CO
2 [ppm
]
C
O [p
pb]
CO offset
How well can we quantitatively
use CO
as a fossil fuel CO2 surrogate ?
Weighted mean ratio [ppb/ppm]:
Observations: 12.2±0.4
Fossil fuel CO2 and CO offset and their ratio
2001 2002 2003 20040
200
400
2001 2002 2003 20040
10
20
30
2001 2002 2003 20040
10
20
30fossil fuel CO
2
CO
2 [pp
m]
C
O [p
pb
]
CO offset
ratio
[pp
b/p
pm
]
CO/CO2foss
Weighted mean ratios [ppb/ppm]:
Observations: 12.2±0.4
Emissions Inventories (incl. soils, etc.)
Edgar: 14.7
Fossil fuel CO2 and CO offset and their ratio in comparison with emissions
inventories
2001 2002 2003 20040
200
400
2001 2002 2003 20040
10
20
30
2001 2002 2003 20040
10
20
30fossil fuel CO
2
CO
2 [pp
m]
C
O [p
pb
]
CO offset
EDGAR
ratio
[pp
b/p
pm
]
CO/CO2foss
Weighted mean ratios [ppb/ppm]:
Observations: 12.2±0.4
Emissions Inventories (incl. soils, etc.)
IER: 18.0Edgar: 14.7
Fossil fuel CO2 and CO offset and their ratio in comparison with emissions
inventories
2001 2002 2003 20040
200
400
2001 2002 2003 20040
10
20
30
2001 2002 2003 20040
10
20
30fossil fuel CO
2
CO
2 [pp
m]
C
O [p
pb
]
CO offset
IER EDGAR
ratio
[pp
b/p
pm
]
CO/CO2foss
IER: Institute of Energy Economics and Rational Use of Energy, Stuttgart
Conclusions (I):
• Fossil fuel CO2 (FFCO2) emissions in Europe contribute almost half to the continental CO2 signal
• Monthly mean fossil fuel CO2 levels at urban sites can be determined by high precision 14CO2 measurements to better than ±10% in winter and about ±30% in summer.
• At remote sites, the mean FFCO2 signal is small (1-5 ppm) and can be determined by 14CO2 measurements only to about 30%. Higher temporal resolution of 14CO2 measurements is required here to achieve better precision.
Conclusions (II):
CO is a potentially applicable surrogate tracer for FFCO2,
however,
• Emissions inventories of CO (and FFCO2) are yet not accurate enough to apply it quantitatively,
• CO has sources other than from fossil fuel burning (soils !!) which also need to be known accurately
• The catchment area and relative mix of emissions needs to be known accurately, this requires modelling
See REMO results from Karstens et al., Poster FF-134
Thank you !
Comparison of measured and REMO-modelled CO and FFCO2 mixing
ratios
Comparison of measured and REMO-modelled CO/FFCO2 ratios
See also Poster by Ute Karstens et al. No. FF-134
Mean ratios [ppb/ppm]:
Observations: 13.5±0.6
REMO & EDGAR: 12.7±0.1
REMO & IER: 11.0±0.2
CO/CO2 fossil fuel emission ratios 2000
IER mean 2000(Scholz et al., IER 2005)
EDGAR V3.2 FT 2000 (Olivier et al., 2005)
in mmol / mol
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