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| Titel |
Molecular hydrogen (H2) combustion emissions and their isotope (D/H) signatures from domestic heaters, diesel vehicle engines, waste incinerator plants, and biomass burning |
| VerfasserIn |
M. K. Vollmer, S. Walter, J. Mohn, M. Steinbacher, S. W. Bond, T. Röckmann, S. Reimann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 14 ; Nr. 12, no. 14 (2012-07-19), S.6275-6289 |
| Datensatznummer |
250011327
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| Publikation (Nr.) |
 copernicus.org/acp-12-6275-2012.pdf |
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| Zusammenfassung |
| Molecular hydrogen (H2), its stable isotope signature (δD), and the
key combustion parameters carbon monoxide (CO), carbon dioxide (CO2), and
methane (CH4) were measured from various combustion processes. H2 in
the exhaust of gas and oil-fired heaters and of waste incinerator plants was
generally depleted compared to ambient intake air, while CO was significantly
elevated. These findings contradict the often assumed co-occurring net H2
and CO emissions in combustion processes and suggest that previous H2
emissions from combustion may have been overestimated when scaled to CO
emissions. For the gas and oil-fired heater exhausts, H2 and δD
generally decrease with increasing CO2, from ambient values of
~0.5 ppm and +130‰ to 0.2 ppm and −206‰,
respectively. These results are interpreted as a combination of an
isotopically light H2 source from fossil fuel combustion and a D/H kinetic
isotope fractionation of hydrogen in the advected ambient air during its
partial removal during combustion. Diesel exhaust measurements from
dynamometer test stand driving cycles show elevated H2 and CO emissions
during cold-start and some acceleration phases. While H2 and CO emissions
from diesel vehicles are known to be significantly less than those from
gasoline vehicles (on a fuel-energy base), we find that their molar H2/CO
ratios (median 0.026, interpercentile range 0.12) are also significantly less
compared to gasoline vehicle exhaust. Using H2/CO emission ratios, along
with CO global emission inventories, we estimate global H2 emissions for
2000, 2005, and 2010. For road transportation (gasoline and diesel), we
calculate 8.3 ± 2.2 Tg, 6.0 ± 1.5 Tg, and 3.8 ± 0.94 Tg,
respectively, whereas the contribution from diesel vehicles is low
(0.9–1.4%). Other fossil fuel emissions are believed to be negligible
but H2 emissions from coal combustion are unknown. For residential
(domestic) emissions, which are likely dominated by biofuel combustion,
emissions for the same years are estimated at 2.7 ± 0.7 Tg,
2.8 ± 0.7 Tg, and 3.0 ± 0.8 Tg, respectively. For biomass burning H2
emissions, we derive a mole fraction ratio ΔH2/ΔCH4
(background mole fractions subtracted) of 3.6 using wildfire emission data
from the literature and support these findings with our wood combustion
results. When combining this ratio with CH4 emission inventories, the
resulting global biomass burning H2 emissions agree well with published
global H2 emissions, suggesting that CH4 emissions may be a good proxy
for biomass burning H2 emissions. |
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