Meanwhile, this material has been published as an open access journal article http://www.sciencedirect.com/science/article/pii/S1352231016307762

1. δD(H2
) at the Cabauw tall tower in the Netherlands
A.M. Batenburg1,2
, M.E. Popa1
, A.T. Vermeulen3
,
W.C.M. van den Bulk3
, P.A.C. Jongejan3
and T. Röckmann1
1
Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
2
Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
3
Energy research Centre of the Netherlands, Petten, the Netherlands
annekebatenburg@gmail.com
Fig 1: Land cover map of the
region around the station (Popa
et al., 2011)
H2
and the Cabauw tall tower
Molecular hydrogen (H2
) might come into wide use
as an energy carrier, but the potential atmospheric
impacts are not well understood. We studied the H2
cycle by measuring both the H2
mixing ratio (χ(H2
))
and its isotopic composition (δD(H2
)) in samples
taken at the Cabauw tall tower.
The Cabauw tower at the CESAR site is located in a
relatively rural, central part of the Netherlands,
within tens of kilometers from the four major Dutch
cities (Fig. 1). Its tubing system has inlets at 20, 60,
120 and 200 m.
Fig 2: (a) χ(H2
) and (b) δD(H2
) timeseries of the
flask samples from Cabauw and Mace Head
(Batenburg et al., 2011). Grey solid lines are fits
to the Mace Head data. Open symbols indicate
datapoints that did not pass quality control.
Time series
Fig. 2 shows our time series of χ(H2
)
and δD(H2
) at Cabauw, together
with similar data from Mace Head
on the Irish west coast. The Mace
Head χ(H2
) data form the lower
bound of the Cabauw χ(H2
) data
(Fig. 2(a)). Especially in winter, clear
excursions to high χ(H2
) values
occur regularly at Cabauw. These
χ(H2
) peaks are associated with
very low δD(H2
) values (Fig. 2(b)).
These features indicate that
Cabauw is heavily influenced by H2
from surface sources, which
produce H2
that is depleted in
deuterium.
Fig 3: (a)”Keeling“ plot of (δD(H2
) vs. inverse χ(H2
)) of all Cabauw flask data, with bivariate linear
fit. Grey bar indicates y-axis intercept and error. (b) Distribution of intercepts obtained from a
bootstrapping procedure where the linear Keeling fit was applied to random samples of the data.
Pollution δD(H2
) signature
We estimated the isotopic signature of the Cabauw source mix from the y-
intercept of a linear fit to a“Keeling”plot (δD(H2
) plotted vs 1/χ(H2
), (Fig. 3(a)).
To obtain a realistic error estimate of this source signature, and to account for
possible arbitrariness in our quality control, we applied a bootstrapping rou-
tine where the fit is applied to random samples of the data. The resulting dis-
tribution of intercepts is shown in Fig. 3(b). There is considerable spread in
the intercepts, but almost all are below -400 ‰.
This signature is more D-depleted than any published source signature for H2
from combustion sources. Possible explanations are that catalytic converters
and certain (congested) driving conditions can lower the fossil fuel combus-
tion source signature (Vollmer et al., 2010), and/or that extremely D-depleted
H2
from microbial sources in the soil contributes to the mix (Chen et al., 2015).
Flask χ(H2
) and δD(H2
) profiles
Cabauw is the only location where vertical profiles of δD(H2
) in
the boundary layer have been obtained (Fig. 4). Lower χ(H2
)
values and higher δD(H2
) values are expected close to the
ground at locations with strong soil uptake. Fig. 4 does not
show this, probably because of the soil type (peat/clay) and
high ground water table.
χ(H2
) is significantly higher at 20 m than at 200 m, and δD(H2
)
is significantly lower at the lower than at the higher levels.This
may point to a difference in the source signature between H2
emitted in the different footprint regions of the different
levels.
Fig 4: Box plots of χ(H2
)(a) and δD(H2
)(b) on days where more than two sampling
heights were sampeled. Red lines indicate medians, box edges indicate lower
and upper quartiles and whiskers indicate lower and upper 95th
percentiles
Conclusions
δD(H2
) observations at this anthropogenically influenced site
complement observations at background locations, provide
information on the H2
cycle in densely populated regions and
help in assessing the atmospheric impacts of future H2
emissions. Here, emissions that add H2
above background
levels show a source signature that is more D-depleted than
literature values for combustion processes. The sampling at
different heights provides additional information.
References
M.E. Popa et al., ACP, 11,6425-6443, 2011, doi:10.5194/acp-11-6425-2011
A. M. Batenburg et al., ACP, 11, 6985-6999, 2011, doi:10.5194/acp-11-6985-2011
M. K. Vollmer et al., ACP, 10, 5707-5718, 2010, doi:10.5194/acp-10-5707-2010
Q. Chen et al., ACPD, 15, 23457-23506, doi:10.5194/acpd-15-23457-2015, 2015