Poster presented at European Geosciences Union General Assembly 2011. This work was later published in ACPD, see http://www.atmos-chem-phys-discuss.net/12/589/2012/acpd-12-589-2012.html. Please include a proper attribution when using this work. This work is not intended for commercial use.

1. Correlations between δ(D,H2) and methane (CH4) in the UTLS region obtained from CARIBIC samples
A.M. Batenburg1, T.J. Schuck2, A. Baker2, C.A.M. Brenninkmeijer2 and T. Röckmann1
1
Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, the Netherlands
2
Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, Germany
www.caribic-atmospheric.com
Atmospheric H2 and the CARIBIC project Flights to Caracas
If H2 comes into wide use as a fuel, its atmospheric levels may In total, 490 samples from 21 return flights
rise (due to leakage) above present-day levels (≈ 0.5 ppm). This have been analyzed for H2 mixing ratios
may affect the atmosphere’s oxidative capacity and stratospher- (m(H2)) and δ(D,H2) at the IMAU isotope labo-
ic ozone chemistry. Unfortunately, large uncertainties still exist ratory. Fig. 2 shows results of 7 flights with
in the global H2 budget. destination Caracas.
The different sources and sinks of H2 have distinct isotope ef- Some samples seem affected by pollution (a
fects. Therefore, measurements of isotopic composition high m(H2) and low δ(D,H2) value). This tends
(deuterium content, expressed as δ(D,H2)) are a promising tool to occur in samples that were taken around
to constrain the terms in the global budget. take-off and landing of the aircraft (e.g. flight
The CARIBIC project uses an automated instrument container 286 and 266, values are off the figure scale).
Fig.1: The aircraft (Lufthansa on board of a commercial passenger aircraft to carry out in-situ
Airbus A340-600) and the at- With meteorological and chemical data, sam-
tached inlet system used for measurements and collect air samples. The resulting samples ples with stratospheric influence can be
CARIBIC. are mostly from the Upper Troposphere-Lower Stratosphere identified. These samples often show a clear
(UTLS) region, an interesting, but little studied, part of the at- Fig.2: m(H2) (a) and δ(D,H2) (b) data from flights to Caracas, Venezuela. Stratosphere- elevation in δ(D,H2) .
mosphere. influenced samples are shown with open symbols.
CH4 oxidation Stratosphere data Monsoon flights Conclusions
156 samples contain air from the lower stratosphere. Previ- Schuck et al. (2010) found A large number of CARIBIC samples
D-enriched H2:
H2
δ(D,H2) increase ously it was found that in the stratosphere, the competing increased levels of CH4 in were analyzed for m(H2) and δ(D,H2).
production
production and destruction processes for H2 balance out, flights to India during • For the stratosphere the number of
but that these do cause a strong deuterium enrichment summer monsoon. available δ(D,H2) observations has in-
H2 with δ(D,H2) (Fig.3). δ(D,H2) shows a compact correlation with methane No enhancement was creased fivefold, and they provide in-
(CH4), which is destroyed as H2 is produced. found in m(H2), but the formation about the stratospheric H2
H2 Preferential re- In the CARIBIC data, δ(D,H2) is also strongly correlated with samples with increased cycle.
destruction moval of H over D:
δ(D,H2) increase
CH4, whereas m(H2) is not (Fig. 4 (a)). The correlation’s slope is methane showed a de- • First observations of δ(D,H2) in the
very similar to the one found in a stratospheric balloon flight crease in δ(D,H2) that is cor- summer monsoon were made. These
oxidation by OH (Röckmann et al., 2003) (Fig. 4(b)). That this effect is found in related to m(CH4) (Fig.5 contain an interesting correlation
samples from different geographic locations and altitudes and 6). with the CH4 increase in this season,
Fig.3: A cartoon representation of
the the stratospheric H2 cycle shows that this correlation likely holds globally. This δ(D,H2)decrease in the which may point to an as yet unstud-
`Monsoon plume’ is prob- Fig.5: m(CH4) (a) and δ(D,H2)(b) measured on tropospheric ied microbial H2 source.
ably caused by increased samples from flights to India south of 400 N in the summer
• These samples from the UTLS region
convection, bringing H2 monsoon (July-Sept,green shades) and after monsoon
(Okt-Nov, reddish colors). are complementary to observations
that is depleted in D from
from ground stations and ship cruises
surface sources to cruising
and will help in constraining the un-
altitude.
certainties in the H2 budget and vali-
That no simultaneous H2
dating models.
increase is seen, may indi-
cate a contribution from a
very depleted source. In- References
creased microbial produc- - Röckmann et al., Heavy hydrogen in the strato-
sphere, Atmos. Chem. Phys 3, 2015-2023, 2003
tion in the wet season is - Schuck et al, Greenhouse gas relationships in the
much more strongly de- Indian summer monsoon plume measured by the
pleted than combustion CARIBIC passenger aircraft, Atmos. Chem. Phys. 11,
sources (≈ -700‰, resp. 503-518, 2011
Fig.4 (a): m(H2) and δ(D,H2) plotted against methane mixing ratio (m(CH4)), with fits through the data. (b): δ(D,H2) Fig.6: δ(D,H2) plotted against m(CH4) for the monsoon
plotted against m(CH4) for the CARIBIC samples and literature values (Röckmann et al., 2003) ≈ -200‰). samples in Fig.5, with linear fit.
Questions: a.m.batenburg@uu.nl