[Show abstract][Hide abstract] ABSTRACT: Methyl chloroform (MCF) is a man-made chlorinated solvent contributing to the destruction of stratospheric ozone and is controlled under the Montreal Protocol on Substances that Deplete the Ozone Layer. Long-term, high-frequency observations of MCF carried out at three European sites show a constant decline of the background mixing ratios of MCF. However, we observe persistent non-negligible mixing ratio enhancements of MCF in pollution episodes suggesting unexpectedly high ongoing emissions in Europe. In order to identify the source regions and to give an estimate of the magnitude of such emissions, we have used a Bayesian inversion method and a point source analysis, based on high-frequency long-term observations at the three European sites. The inversion identified south-eastern France (SEF) as a region with enhanced MCF emissions. This estimate was confirmed by the point source analysis. We performed this analysis using an eleven-year data set, from January 2002 to December 2012. Overall emissions estimated for the European study domain decreased nearly exponentially from 1.1 Gg yr-1 in 2002 to 0.32 Gg yr-1 in 2012, of which the estimated emissions from the SEF region accounted for 0.49 Gg yr-1 in 2002 and 0.20 Gg yr-1 in 2012. The European estimates are a significant fraction of the total semi-hemisphere (30-90° N) emissions, contributing a minimum of 9.8% in 2004 and a maximum of 33.7% in 2011, of which on average 50% are from the SEF region. On the global scale, the SEF region is thus responsible from a minimum of 2.6% (in 2003) to a maximum of 10.3% (in 2009) of the global MCF emissions.
[Show abstract][Hide abstract] ABSTRACT: High frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first in situ global measurements of these two gases. HFC-143a and HFC-32 are the third and sixth most abundant HFCs respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 and 0.7 mW m2 in 2012, respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1-sigma) in the lower troposphere and its growth rate was 1.4 ± 0.04 ppt yr-1; HFC-32 had a global mean mole fraction of 6.2 ± 0.2 ppt and a growth rate of 1.1 ± 0.04 ppt yr-1 in 2012. The extensive observations presented in this work have been combined with an atmospheric transport model to simulate global atmospheric abundances and derive global emission estimates. It is estimated that 23 ± 3 Gg yr-1 of HFC-143a and 21 ± 11 Gg yr-1 of HFC-32 were emitted globally in 2012, and the emission rates are estimated to be increasing 7 ± 5% yr-1 for HFC-143a and 14 ± 11% yr-1 for HFC-32.
[Show abstract][Hide abstract] ABSTRACT: Measurements of CO2, CO, N2O and CH4 mole fractions, O2 / N2 ratios and the stable isotopes 13C and 18O in CO2 and CO have been performed in air samples from the Islisberg highway tunnel (Switzerland). The molar CO : CO2 ratios, with an average of (4.15 ± 0.34) ppb:ppm, are lower than reported in previous studies, pointing to a reduction in CO emissions from traffic. The 13C in CO2 reflects the isotopic composition of the fuel. 18O in CO2 is slightly depleted compared to the 18O in atmospheric O2, and shows significant variability. In contrast, the δ13C values of CO show that significant fractionation takes place during CO destruction in the catalytic converter. 13C in CO is enriched by 3‰ compared to the 13C in the fuel burnt, while the 18O content is similar to that of atmospheric O2. We compute a fractionation constant of (−2.7 ± 0.7)‰ for 13C during CO destruction. The N2O : CO2 average ratio of (1.8 ± 0.2) × 10−2 ppb:ppm is significantly lower than in past studies, showing a reduction in N2O emissions likely related to improvements in the catalytic converter technology. We also observed small CH4 emissions, with an average CH4 : CO2 ratio of (4.6 ± 0.2) × 10−2 ppb:ppm. The O2 : CO2 ratios of (−1.47 ± 0.01) ppm:ppm are very close to the expected, theoretically calculated values of O2 depletion per CO2 enhancement.
ATMOSPHERIC CHEMISTRY AND PHYSICS 02/2014; 14(4):2105-2123. · 5.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Noble gases are widely used in oceanography and limnology, groundwater research, geo/cosmochronology, environmental and climate research. Gas standards for calibration of noble gas analyses are commonly derived from aliquots of ambient air. However, the atmospheric noble gas abundances are seasonally variable due varying air/ocean partitioning. Also, evidence for geographical variabilities of the 3He/4He ratio have been reported recently. Finally, and maybe most importantly, numerous studies considered a potential anthropogenic increase of the atmospheric He concentration and a corresponding decrease in the 3He/4He ratio during the past decades. The changes in the atmospheric noble gas composition are small, but may become significant in comparison of data determined using different air standards. We therefore suggest to collect a large amount of air which would serve as a common reference available to all noble gas laboratories. This reference could further be used to produce standards spiked with small and well known amounts of purified noble gases. We hereby invite the noble gas community to discuss the needs, requirements, and possibilities for such a community standard.
[Show abstract][Hide abstract] ABSTRACT: The long-term evolution of the vertical column abundance of carbon
tetrafluoride (CF4) above the high altitude Jungfraujoch
station (Swiss Alps, 46.5 °N, 8.0 °E, 3580 m a.s.l.) has been
derived from the spectrometric analysis of Fourier transform infrared
solar spectra recorded at that site between 1989 and 2012. The
investigation is based on a multi-microwindow approach, two encompassing
pairs of absorption lines belonging to the strong ν3 band
of CF4 centered at 1283 cm-1, and two additional
ones to optimally account for weak but overlapping HNO3
interferences. The analysis reveals a steady accumulation of the very
long-lived CF4 above the Jungfraujoch at mean rates of (1.38
± 0.11) × 1013 molec cm-2
yr-1 from 1989 to 1997, and (0.97 ± 0.02) ×
1013 molec cm-2 yr-1 from 1998 to 2012,
which correspond to linear growth rates of 1.71 ± 0.14 and 1.04
± 0.02% yr-1, respectively referenced to 1989 and
1998. Related global CF4 emissions required to sustain these
mean increases correspond to 15.8 ± 1.3 and 11.1 ± 0.2 Gg
yr-1 over the above specified time intervals. Findings
reported here are compared and discussed with respect to relevant
results obtained remotely from space and balloons as well as in situ on
the ground, including new gas chromatography mass spectrometry
measurements performed at the Jungfraujoch since 2010.
[Show abstract][Hide abstract] ABSTRACT: We report in situ atmospheric measurements of HFC-43-10mee (C5H2F10, 1,1,1,2,2,3,4,5,5,5-decafluoropentane) from seven observatories at various latitudes, together with measurements of archived air samples and recent Antarctic flask air samples. The global mean tropospheric abundance was 0.21 ± 0.05 ppt (parts-per-trillion, dry air mole fraction) in 2012, rising from 0.04 ± 0.03 ppt in 2000. We combine the measurements with a model and inverse method to estimate rising global emissions –– from 0.43 ± 0.34 Gg yr-1 in 2000 to 1.13 ± 0.31 Gg yr-1 in 2012 (~1.9 Tg CO2-eq yr-1 based on a 100-yr global warming potential of 1,660). HFC-43-10mee –– a cleaning solvent used in the electronics industry –– is currently a minor contributor to global radiative forcing relative to total HFCs; however, our calculated emissions highlight a significant difference from the available reported figures and projected estimates.
Geophysical Research Letters 01/2014; · 3.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The growing awareness of climate change/global warming and continuing concerns regarding stratospheric ozone depletion will require future measurements and standards for many compounds, in particular halocarbons that are linked to these issues. In order to track and control the emissions of these species globally in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. This report describes the results of a pilot study between National Metrology Institutes and atmospheric research laboratories for several of the more important halocarbons at atmospheric concentration levels. The comparison includes the chlorofluorocarbons (CFCs) dichlorodifluoromethane (CFC 12), trichlorofluoromethane (CFC 11), and 1,1,2-trichlorotrifluoroethane (CFC 113); the hydrochlorofluorocarbons (HCFCs) chlorodifluoromethane (HCFC 22) and 1-chloro-1,1-difluoroethane (HCFC 142b); and the hydrofluorocarbon (HFC) 1,1,1,2-tetrafluoroethane (HFC 134a), all in a dried whole air sample. The objective of this key comparison is to compare the measurement capabilities of the participants for these halocarbons at trace atmospheric levels.
[Show abstract][Hide abstract] ABSTRACT: This work reassesses the global atmospheric budget of H2 with
the TM5 model. The recent adjustment of the calibration scale for
H2 translates into a change in the tropospheric burden.
Furthermore, the ECMWF Reanalysis-Interim (ERA-Interim) data from the
European Centre for Medium-Range Weather Forecasts (ECMWF) used in this
study show slower vertical transport than the operational data used
before. Consequently, more H2 is removed by deposition. The
deposition parametrization is updated because significant deposition
fluxes for snow, water, and vegetation surfaces were calculated in our
previous study. Timescales of 1-2 h are asserted for the transport of
H2 through the canopies of densely vegetated regions. The
global scale variability of H2 and δ[DH2] is
well represented by the updated model. H2 is slightly
overestimated in the Southern Hemisphere because too little
H2 is removed by dry deposition to rainforests and savannahs.
The variability in H2 over Europe is further investigated
using a high-resolution model subdomain. It is shown that discrepancies
between the model and the observations are mainly caused by the finite
model resolution. The tropospheric burden is estimated at 165±8
Tg H2. The removal rates of H2 by deposition and
photochemical oxidation are estimated at 53±4 and 23±2 Tg
H2/yr, resulting in a tropospheric lifetime of 2.2±0.2
Also accessible through Utrecht University repository: http://dspace.library.uu.nl/handle/1874/275776
Journal of Geophysical Research 05/2013; · 3.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Traffic is one of the main sources of CO2 and CO in highly populated
regions like Western Europe. 13C and 18O isotopic signatures of
traffic-emitted CO2 and CO were determined form air samples collected in
the Islisberg highway tunnel (Switzerland), during a measurement and
sampling campaign in 2011. The goal of the campaign was to characterize
traffic emissions of the present west European vehicle fleet, at
integrated fleet level. The isotopic composition of traffic CO2
reflects on average the isotopic composition of the fuel (13C) and of
atmospheric oxygen (18O), although the 18O values are quite variable. In
contrast, the isotopic values of CO show that significant fractionation
takes place during CO formation (18O) and during the subsequent, partial
CO destruction in the catalytic converter (13C). The 13C is enriched by
3 ‰ compared to the 13C in the fuel burnt, while the 18O is
depleted by 7 ‰ compared to the 18O in atmospheric oxygen. We
compute a kinetic isotope effect for 13C during CO destruction of 2.5
± 0.7 ‰. The average 18O in traffic CO is 17 ‰
(VSMOW), similar to the biomass burning signature previously determined
in Switzerland and Europe (e.g. Saurer et al., 2009). Thus, in the
conditions represented by our study (Swiss fleet, highway driving
conditions), the traffic and biomass burning CO emissions cannot be
distinguished anymore based on 18O signature alone. References Saurer,
M., Prévôt, A. S. H., Dommen, J., Sandradewi, J.,
Baltensperger, U., and Siegwolf, R. T. W.: The influence of traffic and
wood combustion on the stable isotopic composition of carbon monoxide,
Atmos. Chem. Phys., 9, 3147-3161, doi:10.5194/acp-9-3147-2009, 2009.
[Show abstract][Hide abstract] ABSTRACT: Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived
ozone depleting halocarbons, in particular the chlorofluorocarbons
(CFCs). Given the complete ban of the CFCs by the Montreal Protocol, its
Amendments and Adjustments, HCFCs are on the rise, with current rates of
increase substantially larger than at the beginning of the 21st century.
HCFC-142b (CH3CClF2) is presently the second most abundant HCFCs, after
HCFC-22 (CHClF2). It is used in a wide range of applications, including
as a blowing foam agent, in refrigeration and air-conditioning. Its
concentration will soon reach 25 ppt in the northern hemisphere, with
mixing ratios increasing at about 1.1 ppt/yr [Montzka et al., 2011]. The
HCFC-142b lifetime is estimated at 18 years. With a global warming
potential of 2310 on a 100-yr horizon, this species is also a potent
greenhouse gas [Forster et al., 2007]. First space-based retrievals
of HCFC-142b have been reported by Dufour et al. . 17 occultations
recorded in 2004 by the Canadian ACE-FTS instrument (Atmospheric
Chemistry Experiment - Fourier Transform Spectrometer, onboard SCISAT-1)
were analyzed, using two microwindows (1132.5-1135.5 and 1191.5-1195.5
cm-1). In 2009, Rinsland et al. determined the HCFC-142b trend near the
tropopause, from the analysis of ACE-FTS observations recorded over the
2004-2008 time period. The spectral region used in this study extended
from 903 to 905.5 cm-1. In this contribution, we will present the
first HCFC-142b measurements from ground-based high-resolution Fourier
Transform Infrared (FTIR) solar spectra. We use observations recorded at
the high altitude station of the Jungfraujoch (46.5°N, 8°E, 3580
m asl), with a Bruker 120HR instrument, in the framework of the Network
for the Detection of Atmospheric Composition Change (NDACC, visit
http://www.ndacc.org). The retrieval of HCFC-142b is very challenging,
with simulations indicating only weak absorptions, lower than 1% for low
sun spectra and current concentrations. Among the four microwindows
tested, the region extending from 900 to 906 cm-1 proved to be the most
appropriate, with limited interferences, in particular from water vapor.
A total column time series spanning the 2004-2012 time period will be
presented, analyzed and critically discussed. After conversion of our
total columns to concentrations, we will compare our results with in
situ measurements performed in the northern hemisphere by the AGAGE
network. Acknowledgments The University of Liège
contribution to the present work has primarily been supported by the SSD
and PRODEX programs (AGACC-II and A3C projects, respectively) funded by
the Belgian Federal Science Policy Office (BELSPO), Brussels. E. Mahieu
is Research Associate with the F.R.S. - FNRS. Laboratory developments
and mission expenses at the Jungfraujoch station were funded by the
F.R.S. - FNRS and the Fédération Wallonie-Bruxelles,
respectively. We thank the International Foundation High Altitude
Research Stations Jungfraujoch and Gornergrat (HFSJG, Bern) for
supporting the facilities needed to perform the observations. We further
acknowledge the vital contribution from all the Belgian colleagues in
performing the Jungfraujoch observations used here. References
Dufour, G., C.D. Boone, and P.F. Bernath, First measurements of CFC-113
and HCFC-142b from space using ACE-FTS infrared spectra, Geophys. Res.
Lett., 32, L15S09, doi:10.1029/2005GL022422, 2005. Forster, P., V.
Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J.
Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and
R. Van Dorland, 2007: Changes in Atmospheric Constituents and in
Radiative Forcing. In: Climate Change 2007: The Physical Science Basis.
Contribution of Working Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M.
Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and New
York, NY, USA. Montzka, S.A., S. Reimann, A. Engel, K. Krüger,
S. O'Doherty, W.T. Sturges, D. Blake, M. Dirf, P. Fraser, L. Froidevaux,
K. Jucks, K. Kreher, M.J. Kurylo, A. Mellouki, J. Miller, O.-J. Nielsen,
V.L. Orkin, R.G. Prinn, R. Shew, M.L. Santee, A. Stohl, and D. Verdonik,
Ozone-Depleting Substances (ODSs) and Related Chemicals, Chapter 1 in
Scientific Assessment of Ozone Depletion: 2010, Global Ozone Research
and Monitoring Project-Report No. 52, 516 pp., World Meteorological
Organization, Geneva, Switzerland, 2011. Rinsland, C.P., L.S. Chiou,
C.D. Boone, P.F. Bernath, and E. Mahieu, First Measurements of the
HCFC-142b trend from Atmospheric Chemistry Experiment (ACE) Solar
Occultation Spectra, J. Quant. Spectrosc. Radiat. Transfer, 110,
[Show abstract][Hide abstract] ABSTRACT: The evolution of the atmospheric noble gas composition during the past few decades has hardly been studied because, in contrast to many other atmospheric gases, systematic time-series measurements have not been available. Based on theoretical considerations, the atmospheric noble gas isotope composition is assumed to be stable on time scales of up to about 106 yrs, with the potential exception of anthropogenic changes predicted for the He concentration and the 3He/4He ratio. However, experimental assessments of the predicted changes in the atmospheric He isotope composition are controversial. To empirically test these assumptions and predictions, we analysed the noble gas isotope composition in samples of the Cape Grim Air Archive, a well-defined archive of marine boundary layer air in the southern hemisphere. The resulting time series of the 20Ne, 40Ar, 86Kr and 136Xe concentrations and 20Ne/22Ne and 40Ar/36Ar ratios during 1978–2011 demonstrate the stability of the atmospheric Ne, Ar, Kr and Xe composition during this time interval. The He isotope data indicate a decrease in the 3He/4He during the same time interval at a mean rate of 0.23–0.30‰0.23–0.30‰ per yr. This result is consistent with most model predictions of the rate of decrease in the atmospheric 3He/4He ratio associated with mining and burning of fossil fuels.
[Show abstract][Hide abstract] ABSTRACT: The effect of intercontinental transport on measurements of nitrogen oxides (NOx), peroxyacetyl nitrate (PAN) and reactive nitrogen species (NOy) at the high altitude site Jungfraujoch (3580 m asl), Switzerland, was evaluated using a combination of backward trajectories and chemical filters (NOy to carbon monoxide (CO) ratio). Mixing ratios associated with air masses transported from the planetary boundary layers (PBL) of the three continental source regions Europe, North America, and Asia, and of free tropospheric origin were characterized. The analysis was applied to PAN, NOx and NOy measurements of the period 1997–1998, and to a period more than 10 years later covering several months in 2008 and 2009–2010. The results show that the mixing ratios of PAN, NOx and NOy are largest in air advected from the European PBL. In contrast to previous studies, our results indicate that the springtime maximum in PAN and NOy mixing ratios is largely attributable to air originating from the European PBL whereas air of free tropospheric origin and intercontinental transport contribute less significantly. PAN and NOy mixing ratios in air masses classified as free tropospheric are also highest in spring but substantially lower than those influenced by European PBL air. Air masses last influenced by the North American source region show considerably lower mixing ratios of nitrogen species than European air masses suggesting that a large fraction of NOy is removed during intercontinental transport probably due to washout of soluble species such as HNO3. The seasonal contributions from different source regions to PAN mixing ratios at Jungfraujoch were evaluated. The average European contribution is highest during the warm seasons with 47–57% in 1997–1998 and 61–69% in 2009–2010. The maximum contribution of North American air masses is also observed in the warm season and was about 5–7% in 1997–1998 and 6–10% in 2009–2010. Air from Asian source regions did not make a significant contribution due to the limited number of cases of direct transport from Asia, but when they occurred the air masses contained significant pollutant levels.
[Show abstract][Hide abstract] ABSTRACT: The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse and ozone depleting gases. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement among commonly used calibration scales for a number of trace gases present in the unpolluted atmosphere at pmol mol<sup>−1</sup> (parts per trillion) levels, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Some scale relationships were found to be consistent with those derived from bi-lateral experiments or from analysis of atmospheric data, while others revealed discrepancies. The transfer of calibration scales among laboratories was found to be problematic in many cases, meaning that measurements tied to a common scale may not, in fact, be compatible. These results reveal substantial improvements in calibration over previous comparisons. However there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.
[Show abstract][Hide abstract] ABSTRACT: Atmospheric HCFC-22 (CHClF2) and HCFC-142b (CH3CClF2) in-situ measurements have been recorded by an automated gas chromatograph-electron capture detectors (GC-ECDs) system and a gas chromatography/mass spectrometry (Medusa-GC/MS) system at the Global Atmosphere Watch (GAW) regional background station Shangdianzi (SDZ), China. The mixing ratios of the two HCFCs at SDZ show frequent events with elevated concentrations due to polluted air from urban or industrialized areas. The mean background mixing ratios for HCFC-22 and HCFC-142b were 205.3 ppt (parts per trillion, 10−12, molar) and 20.7 ppt, respectively, for the study period (March 2007–February 2011). The yearly background mixing ratios for the two HCFCs at SDZ are similar to those measured at Trinidad Head and Mace Head located in the Northern Hemisphere (NH), but larger than Cape Grim and Cape Matatula (located in the Southern Hemisphere) due to inter-hemispheric differences caused by predominantly NH emissions. During the study period, background mixing ratios exhibited positive growth rates of 8.7 ppt yr−1 for HCFC-22 and 0.95 ppt yr−1 for HCFC-142b. HCFC’s seasonality exhibits a summer/autumn maximum and a winter minimum. 4-year averaged background seasonal amplitudes (maximum–minimum) are 6.0 ppt for HCFC-22 and 0.9 ppt for HCFC-142b. The seasonal fluctuations (maximum–minimum) in polluted events are 105.4 ppt for HCFC-22 and 29.1 ppt for HCFC-142b, which are much stronger than the fluctuations under background conditions. However, both HCFC-22 and HCFC-142b show summer minima in 2008, which is most likely due to emission control regulations when the Olympic Games were held in Beijing.
[Show abstract][Hide abstract] ABSTRACT: HCFC-22 (CHClF2, chlorodifluoromethane) is an ozone-depleting substance (ODS) as well as a significant greenhouse gas (GHG). HCFC-22 has been used widely as a refrigerant fluid in cooling and air-conditioning equipment since the 1960s, and it has also served as a traditional substitute for some chlorofluorocarbons (CFCs) controlled under the Montreal Protocol. A low frequency record on tropospheric HCFC-22 since the late 1970s is available from measurements of the Southern Hemisphere Cape Grim Air Archive (CGAA) and a few Northern Hemisphere air samples (mostly from Trinidad Head) using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. Since the 1990s high-frequency, high-precision, in situ HCFC-22 measurements have been collected at these AGAGE stations. Since 1992, the Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected flasks on a weekly basis from remote sites across the globe and analyzed them for a suite of halocarbons including HCFC-22. Additionally, since 2006 flasks have been collected approximately daily at a number of tower sites across the US and analyzed for halocarbons and other gases at NOAA. All results show an increase in the atmospheric mole fractions of HCFC-22, and recent data show a growth rate of approximately 4% per year, resulting in an increase in the background atmospheric mole fraction by a factor of 1.7 from 1995 to 2009. Using data on HCFC-22 consumption submitted to the United Nations Environment Programme (UNEP), as well as existing bottom-up emission estimates, we first create globally-gridded a priori HCFC-22 emissions over the 15 yr since 1995. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions. Our inversion indicates that the global HCFC-22 emissions have an increasing trend between 1995 and 2009. We further find a surge in HCFC-22 emissions between 2005 and 2009 from developing countries in Asia – the largest emitting region including China and India. Globally, substantial emissions continue despite production and consumption being phased out in developed countries currently.
Atmospheric Chemistry and Physics. 11/2012; 12:10033-10050.
[Show abstract][Hide abstract] ABSTRACT: Atmospheric hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) were
measured in-situ at the Shangdianzi (SDZ) Global Atmosphere Watch (GAW)
regional background station, China, from May 2010 to May 2011. The time
series for five HFCs and three PFCs showed occasionally
high-concentration events while background conditions occurred for 36%
(HFC-32) to 83% (PFC-218) of all measurements. The mean mixing ratios
during background conditions were 24.5 ppt (parts per trillion,
10-12, molar) for HFC-23, 5.86 ppt for HFC-32, 9.97 ppt for
HFC-125, 66.0 ppt for HFC-134a, 9.77 ppt for HFC-152a, 79.1 ppt for
CF4, 4.22 ppt for PFC-116, and 0.56 ppt for PFC-218. The
background mixing ratios for the compounds at SDZ are consistent with
those obtained at mid to high latitude sites in the Northern Hemisphere.
North-easterly winds were associated with negative contributions to
atmospheric HFC and PFC loadings (mixing ratio anomalies weighted by
time associated with winds in a given sector), whereas south-westerly
advection (urban sector) showed positive loadings. Chinese emissions
estimated by a tracer ratio method using carbon monoxide as tracer were
3.6 ± 3.2 kt yr-1 for HFC-23, 4.3 ± 3.6 kt
yr-1 for HFC-32, 2.7 ± 2.3 kt yr-1 for
HFC-125, 6.0 ± 5.6 kt yr-1 for HFC-134a, 2.0 ±
1.8 kt yr-1 for HFC-152a, 2.4 ± 2.1 kt yr-1
for CF4, 0.27 ± 0.26 kt yr-1 for PFC-116,
and 0.061 ± 0.095 kt yr-1 for PFC-218. The lower
HFC-23 emissions compared to earlier studies may be a result of the
HFC-23 abatement measures taken as part of Clean Development Mechanism
(CDM) projects that started in 2005.
ATMOSPHERIC CHEMISTRY AND PHYSICS 11/2012; 12(21):10181-10193. · 5.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Biologically produced molecular hydrogen (H2) is characterized by a very strong depletion
in deuterium. Although the biological source to the atmosphere is small compared
to photochemical or combustion sources, it makes an important contribution to
the global isotope budget of molecular hydrogen (H2). Large uncertainties exist in the
quantification of the individual production and degradation processes that contribute to
the atmospheric budget, and isotope measurements are a tool to distinguish the contributions
from the different sources. Measurements of δD from the various H2 sources
are scarce and for biologically produced H2 only very few measurements exist. Here
the first systematic study of the isotopic composition of biologically produced H2 is
We investigated δD of H2 produced in a biogas plant, covering different treatments
of biogas production, and from several H2 producing microorganisms such as bacteria
or green algae. A Keeling plot analysis provides a robust overall source sig
nature of δD = –712‰ (±13‰) for the samples from the biogas reactor (at 38 °C,
δDH2O = 73.4 ‰), with a fractionation constant εH2−H2O of –689‰ (±20 ‰). The pure
culture samples from different microorganisms give a mean source signature of δD =
–728‰ (± 39 ‰), and a fractionation constant εH2−H2O of –711‰ (± 45 ‰) between
H2 and the water, respectively. The results confirm the massive deuterium depletion
of biologically produced H2 as was predicted by calculation of the thermodynamic fractionation
factors for hydrogen exchange between H2 and water vapor. As expected
for a thermodynamic equilibrium, the fractionation factor is largely independent of the
substrates used and the H2 production conditions. The predicted equilibrium fractionation
coefficient is positively correlated with temperature and we measured a change
25 of 2.2‰/°C between 45 °C and 60 °C. This is in general agreement with the theoretical predictions.