Stable isotopes and other novel tracers, such as carbonyl sulfide (COS) and clumped isotopes, help to identify and quantify biological, chemical and physical processes that drive Earth's biogeochemical cycling, atmospheric processes and biosphere-atmosphere exchange. Recent developments in analytical measurement techniques now offer the opportunity to investigate these tracers at unprecedented temporal and spatial resolution and precision.

This session includes contributions from field and laboratory experiments, latest instrument developments as well as theoretical and modelling activities that investigate and use the isotope composition of light elements (C, H, O, N) and their compounds as well as other novel tracers for biogeochemical and atmospheric research.

Topics addressed in this session include:
- Stable isotopes in carbon dioxide (CO2), water (H2O), methane (CH4) and nitrous oxide (N2O)
- Novel tracers and biological analogues, such as COS
- Polyisotopocules ("clumped isotopes")
- Intramolecular stable isotope distributions ("isotopomer abundances")
- Analytical, method and modelling developments
- Flux measurements
- Quantification of isotope effects
- Non-mass dependent isotopic fractionation and related isotope anomalies

Public information:
Solicited speaker:
Dr Amaëlle Landais
Laboratoire des sciences du climat et de l’environnement (LSCE)

Co-organized by AS4
Convener: Jan Kaiser | Co-conveners: Alexander Knohl, Lisa Wingate
| Attendance Thu, 07 May, 08:30–10:15 (CEST)

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Download all presentations (118MB)

Chat time: Thursday, 7 May 2020, 08:30–10:15

Chairperson: Jan Kaiser, Lisa Wingate, Alexander Knohl, Thomas Röckmann
D470 |
| Highlight
Amaelle Landais, Ji-Woong Yang, Nicolas Pasquier, Antoine Grisart, Margaux Brandon, Thomas Extier, Frédéric Prié, Bénédicte Minster, Clément Piel, Joana Sauze, Alexandru Milcu, Barbara Stenni, and Thomas Blunier

High precision measurements of triple isotopic composition of oxygen in water is a useful tool to infer the dynamic of past hydrological cycle when measured in ice core together with δ18O and δD. In particular, the triple isotopic composition of oxygen in water provides information on the climatic conditions of the evaporative sources. In parallel, it has been shown that the triple isotopic composition of oxygen in the atmospheric dioxygen can be a useful tracer of the global biosphere productivity and hence reconstruct the dynamic of the global biosphere productivity in the past from measurements performed in the air bubbles. Measuring triple isotopic composition of oxygen both in the water and in the atmospheric dioxygen trapped in bubbles in ice cores is thus a strong added value to study the past variability of water cycle and biosphere productivity in parallel to climate change.

Here, we first present new laboratory experiments performed in closed biological chambers to show how the triple isotopic composition of oxygen in atmospheric dioxygen can be used for quantification of the biosphere productivity with determination of fractionation coefficients. Then, we present new records of triple isotopic composition of oxygen in water and O2 trapped in bubbles from the EPICA Dome C ice core over the deglaciations of the last 800 ka.

How to cite: Landais, A., Yang, J.-W., Pasquier, N., Grisart, A., Brandon, M., Extier, T., Prié, F., Minster, B., Piel, C., Sauze, J., Milcu, A., Stenni, B., and Blunier, T.: Triple isotopic composition of oxygen in water and dioxygen during deglaciations recorded in the EPICA Dome C ice core to link climate, biosphere productivity and water cycle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5961, https://doi.org/10.5194/egusphere-egu2020-5961, 2020

D471 |
Getachew Adnew, Thijs Pons, Gerbrand Koren, Wouter Peters, and Thomas Röckmann



Understanding the processes affecting the triple oxygen isotope composition of atmospheric CO2 during photosynthesis can help to constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions, using sunflower (Helianthus annuus), an annual C3 species with high photosynthetic capacity and stomatal conductance for CO2, an evergreen C3 species, ivy (Hedera hybernica) with lower values for these traits, and a C4 species maize (Zea mays) that has a high photosynthetic capacity and low stomatal conductance. The experiments were conducted at different light intensities and using CO2 with different 17O- excess. Our results demonstrate that two key factors determine the effect of photosynthetic gas exchange on Δ17O of atmospheric CO2: The relative difference in Δ17O of the CO2 entering the leaf and Δ17O of leaf water, and the back-diffusion flux from the leaf to the atmosphere, which can be quantified by the cm/ca ratio.  At low cm/ca the discrimination is governed by diffusion into the leaf, and at high cm/ca by back-diffusion of CO2 that has equilibrated with the leaf water. Plants with a higher cm/ca ratio modify the Δ17O of atmospheric CO2 more strongly than plants with lower cm/ca

Based on the leaf cuvette experiments using both C4 and C3 plants, the global discrimination in 17O-excess of atmospheric CO2 due to assimilation is estimated to be -0.6±0.2‰. The main uncertainty in the global estimation is due to the uncertainty in the cm/ca ratio.




How to cite: Adnew, G., Pons, T., Koren, G., Peters, W., and Röckmann, T.: Leaf-scale quantification of the effect of photosynthetic gas exchange on Δ17O of atmospheric CO2 , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3064, https://doi.org/10.5194/egusphere-egu2020-3064, 2020

D472 |
Simone M. Pieber, Béla Tuzson, Stephan Henne, Ute Karstens, Dominik Brunner, Martin Steinbacher, and Lukas Emmenegger

Evaluating atmospheric transport simulations against observations helps refining bottom-up estimates of greenhouse gas fluxes and identifying gaps in our understanding of regional and category-specific contributions to atmospheric mole fractions. This insight is critical in the efforts to mitigate anthropogenic environmental impact. Beside total mole fractions, stable isotope ratios provide further constraints on source-sink processes [1-3].

Here, we present two receptor-oriented model simulations for carbon dioxide (CO2) mole fraction and δ13C-CO2 stable isotope ratios for a nine year period (2009-2017) at the High Altitude Research Station Jungfraujoch (Switzerland, 3580 m asl). The model simulations of CO2 were performed on a 3-hourly time-resolution with two backward Lagrangian particle dispersion models driven by two different numerical weather forecast fields: FLEXPART-COSMO and STILT-ECMWF. Anthropogenic CO2 fluxes were based on the EDGAR v4.3 emissions inventory aggregated into 14 source categories representing fossil and biogenic fuel uses as well as emissions from cement production. Biospheric CO2 fluxes representing the photosynthetic uptake and respiration of 8 plant functional types were based on the Vegetation Photosynthesis and Respiration Model (VPRM). The simulated CO2 emissions per source and sink category were weighted with category-specific δ13C-CO2 signatures from published experimental studies. Background CO2 values at the boundaries of both model domains were taken from global model simulations and the corresponding δ13C-CO2 values were constructed as suggested in Ref. [3]. We compare the simulations to a unique data set of continuous in-situ observations of CO2 mole fractions and δ13C-CO2 stable isotope ratios by quantum cascade laser absorption spectroscopy as described in previous work [1, 4-5], available for the whole nine year period at the site.

The simulated atmospheric CO2 and δ13C-CO2 time-series are in good agreement with the observations and capture the observed variability at the models' 3-hourly time-resolution. This allows for an in-depth evaluation of the contribution of different CO2 emission sources and for an allocation of source regions when Jungfraujoch is influenced by air masses from the planetary boundary layer. In brief, the receptor-oriented model simulations suggest that anthropogenic CO2 contributions are primarily of fossil origin (90%). Anthropogenic emissions contribute between 60% in February, and 20% in July/August, to the CO2 enhancements observed at Jungfraujoch. The remaining fraction is due to biosphere respiration, which thus largely dominates emissions during the summer season. However, intense photosynthetic CO2 uptake during June, July and August roughly outweighs CO2 contributions from anthropogenic activities and biosphere respiration at JFJ.




[1] Tuzson et al., 2011. ACP, 11, 1685

[2] Röckmann et al., 2016. ACP, 16, 10469

[3] Vardag et al., 2016. Biogeosciences, 13, 4237

[4] Tuzson et al., 2008. Appl. Phys. B, 92, 451

[5] Sturm et al., 2013. AMT 6, 1659

How to cite: Pieber, S. M., Tuzson, B., Henne, S., Karstens, U., Brunner, D., Steinbacher, M., and Emmenegger, L.: Simulations of atmospheric CO2 and δ13C-CO2 compared to real-time observations at the high altitude station Jungfraujoch , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10588, https://doi.org/10.5194/egusphere-egu2020-10588, 2020

D473 |
David Nelson, Zhennan Wang, David Dettman, Barry McManus, Jay Quade, Nitzan Yanay, Katharine Huntington, and Andrew Schauer

Carbon dioxide clumped isotope thermometry is one of the most developed applications of the geochemistry of multiply substituted isotopologues. The degree of heavy isotope clumping (e.g., 16O13C18O) beyond an expected random distribution can be related to the temperature of calcite precipitation. This provides an independent temperature estimate that, when combined with carbonate δ18O values, can constrain paleowater δ18O values. However, the use of isotope ratio mass spectrometry (IRMS) to do these measurements remains relatively rare because it is time-consuming and costly. We have developed an isotope ratio laser spectrometry method using tunable infrared laser differential absorption spectroscopy (TILDAS) and describe our latest results using both gaseous carbon dioxide samples and CO2 derived from carbonate minerals. The TILDAS instrument has two continuous wave lasers to directly and simultaneously measure four isotopologues involved in the 16O13C18O equilibrium calculation. Because each isotopologue is independently resolved, this approach does not have to correct for isobaric peaks. The gas samples are trapped in a low volume (~250 ml) optical multi-pass cell with a path length of 36 meters. Raw data are collected at 1.6 kHz, providing 96,000 peak-area measurements of each CO2 isotopologue per minute. With a specially designed sampling system, each sample measurement is bracketed with measurements of a working reference gas, and a precision of 0.01‰ is achieved within 20 minutes, based on four repeated measurements. The total sample size needed for a complete measurement is approximately 15 μmol of CO2, or 1.5 mg of calcite equivalent. TILDAS reported ∆16O13C18O values show a linear relationship with theoretical calculations, with a very weak dependence on bulk isotope composition. The performance of the TILDAS system demonstrated in this study is competitive with the best IRMS systems and surpasses typical IRMS measurements in several key respects, such as measurement duration and isobaric interference problems. This method can easily be applied more widely in stable isotope geochemistry by changing spectral regions and laser configurations, leading to rapid and high precision (0.01‰) measurement of conventional stable isotope ratios and δ17O in CO2 gas samples.

How to cite: Nelson, D., Wang, Z., Dettman, D., McManus, B., Quade, J., Yanay, N., Huntington, K., and Schauer, A.: Rapid and Precise Carbon Dioxide Clumped Isotope Composition Analysis by Tunable Infrared Laser Differential Absorption Spectroscopy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11501, https://doi.org/10.5194/egusphere-egu2020-11501, 2020

D474 |
Kristýna Kantnerová, Longfei Yu, Daniel Zindel, Mark S. Zahniser, David D. Nelson, Béla Tuzson, Lukas Emmenegger, Mayuko Nakagawa, Sakae Toyoda, Naohiro Yoshida, Stefano M. Bernasconi, and Joachim Mohn

Nitrous oxide (N2O) has been for long a major focus of all greenhouse gas accounting agreements. Understanding the mechanisms of its formation and clarifying its sources and sinks are highly important for mitigating N2O emissions. In this context, measuring the doubly substituted isotopocules of N2O can add new and unique opportunities to fingerprint and constrain the biogeochemical N2O cycle, similar to other atmospheric species such as CO2, CH4, and O2.

We address this challenging research field by developing and validating a laser spectroscopic technique for selective analysis of the eight most abundant N2O isotopic species including the doubly substituted isotopocules 14N15N18O, 15N14N18O, and 15N15N16O. This method is based on quantum cascade laser absorption spectroscopy (QCLAS) and reaches a precision of 0.01 – 0.20 ‰ with 1 – 2 min spectral averaging on samples of 4 μmol of N2O in N2 at 4 hPa.

Furthermore, we have established a new reference frame combining two independent approaches: (1) clumped N2O isotopocule abundances were linked to stochastic distribution by equilibrating the N–O bond in the N2O molecule over activated Al2O3 at 100 and 200 °C, and (2) individual isotopocule concentrations were calibrated using a set of high-accuracy gravimetric N2O-in-N2 gas mixtures. The latter approach, applied for the first time to clumped isotope measurements, has a particular potential in realizing regular multi-point calibration for species like 15N15N16O, because no procedure for equilibration of the N–N bond has been successful yet.

Results of the validation measurements, using the QCLAS method and calibration approach, are presented for a large range of δ values (approx. 100 ‰ for d15N and d18O). Inter-comparison measurements with high-resolution mass spectrometry show compatible results for bulk isotopic composition (d15N, d(458+548)), but superior performance of QCLAS for determining site-selectivity (SP, SP18). In summary, this work provides new methodological basis for the measurements of clumped N2O isotopes and has a high potential to stimulate future research in the N2O community by establishing a new class of reservoir-insensitive tracers and molecular-scale insights.

How to cite: Kantnerová, K., Yu, L., Zindel, D., Zahniser, M. S., Nelson, D. D., Tuzson, B., Emmenegger, L., Nakagawa, M., Toyoda, S., Yoshida, N., Bernasconi, S. M., and Mohn, J.: Clumped isotope analysis in nitrous oxide by mid-IR laser spectroscopy: analytical developments and validation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6726, https://doi.org/10.5194/egusphere-egu2020-6726, 2020

D475 |
Antje Hoheisel, Frank Meinhardt, and Martina Schmidt

Instrumental development in measurement technique now allows continuous in-situ isotope analysis of 13CH4 by Cavity Ring-Down Spectroscopy (CRDS). Analyses of the isotopic composition of methane in ambient air can potentially be used to partition between different CH4 source categories.

Since 2014 a CRDS G2201-i analyser has been used to continuously measure CH4 and its 13C/12C ratio in ambient air at the Institute of Environmental Physics (IUP) in Heidelberg (116m a.s.l.), South-West Germany. Furthermore, the CRDS G2201-i analyser was installed twice for a month at the measurement station of the German Environment Agency at Schauinsland (1205m a.s.l.). In September 2018 and in February 2019 the analyser was moved to Schauinsland to examine the validity of evaluations of continuous δ13CH4 measurements at a semi-rural station.

As an urban station, the seasonal and daily variations of the measured CH4 mole fraction and isotopic composition in Heidelberg vary much stronger than at the mountain station Schauinsland. The precision of the isotopic source signature calculation using a Keeling plot strongly depends on the CH4 peak height and instrumental precision. Therefore, at Schauinsland station the lower variability in the CH4 mole fraction makes the evaluation challenging. Different methods such as monthly/weekly interval evaluations and moving Keeling/Miller Tans methods has been used to calculate the isotopic source signature in ambient air.

The isotopic methane source signatures of the air in Heidelberg was found to be between -75 ‰ and -35 ‰, with an average of (-54 ± 2) ‰. An annual cycle can be noticed with more depleted values (-56 ‰) in summer and more enriched values (-51 ‰) in winter, due to larger biogenic emissions in summer and more thermogenic (e.g. natural gas) emissions in winter. The mean isotopic source signature calculated at Schauinsland shows variations, too, with more enriched values (−56 ‰) in winter and more depleted (−60 ‰) ones in autumn. The more depleted values in summer/autumn at Schauinsland corresponds to more biogenic methane and can be explained by dairy cows grazing near the station especially during this time.

The generally more enriched values at Schauinsland are caused by the more rural surrounding. Emission estimates of county provided by the LUBW Landesanstalt für Umwelt Baden-Württemberg shows that around Schauinsland 60 % of the CH4 emissions are emitted by livestock farming and around Heidelberg only 28 %. The mean isotopic source signature calculated using these emissions is (-58 ± 2) ‰ for Schauinsland and (-53 ± 2) ‰ for Heidelberg. These results agreed well with the mean source signatures determined out of continuous isotopic measurements.

How to cite: Hoheisel, A., Meinhardt, F., and Schmidt, M.: Evaluation of continuous δ13CH4 measurements in Heidelberg and at Schauinsland, Germany, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5761, https://doi.org/10.5194/egusphere-egu2020-5761, 2020

D476 |
Alexis Gilbert, Maxime Julien, Naohiro Yoshida, and Yuichiro Ueno

Hydrocarbons are the main constituents of natural gas. Their chemical and isotope abundance is a window to biogeochemical processes occurring in the subsurface. Stable isotopes of natural gas hydrocarbons are traditionally measured through compound-specific isotope analysis (CSIA) where each hydrocarbon is separated before its isotope ratio is determined.

Recently a variety of methods have been developed to determine position-specific isotope composition of propane, the first hydrocarbon with two distinct isotopomers: central and terminal [1][2][3][4]. The relative abundance of propane isotopomers (e.g. Δ13Ccentral = δ13Ccentral - δ13Cterminal) is a promising tool for tracing sources and sinks of hydrocarbons in natural gas reservoirs. In particular, anaerobic oxidation of propane starts with a fumarate addition at the central position, which is expected to lead to a specific enrichment of the central 13C-isotopomer of the remaining propane.

We measured Δ13Ccentral values of propane throughout the course of its oxidation by bacteria BuS5 [5] and showed that the isotope fractionation is located mainly on the central position, which differs from the signature expected for thermogenic evolution [6]. The approach has been used to detect anaerobic oxidation of propane in several natural gas reservoirs: Southwest Ontario (Canada), Carnarvon Basin (Australia), Michigan (USA) [6], and more recently Tokamachi mud volcano in Japan [7]. In addition, isotopomers of n-butane and i-butane analysed using the same technique allows gaining insights into the mechanism of their microbial oxidation.

The isotopomer approach presented here can thus shed light on the fate of natural gas hydrocarbons. In combination with clumped isotope measurements of methane and ethane, the approach can provide unprecedented information regarding carbon cycling in the subsurface.


[1] Gilbert et al., 2016 GCA v177, p205

[2] Piasecki et al., 2016 GCA v188 p58

[3] Gao et al., 2016 Chem Geol. v435, p1

[4] Liu et al., 2018 Chem Geol. v491, p14

[5] Kniemeyer et al., 2007 Nature v449, p898

[6] Gilbert et al., 2019 PNAS v116, p6653

[7] Etiope et al., 2011 Appl. Geochem. v26, p348

How to cite: Gilbert, A., Julien, M., Yoshida, N., and Ueno, Y.: Isotopomer approaches to the detection of anaerobic oxidation of natural gas hydrocarbons, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13618, https://doi.org/10.5194/egusphere-egu2020-13618, 2020

D477 |
Melanie Egli, Marco M. Lehmann, Nadine Brinkmann, Roland A. Werner, Matthias Saurer, and Ansgar Kahmen

Oxygen isotope analysis of plant material, such as sugars in different tissues, provides an important tool to understand how plants function, interact with their environment and also cope with climate change. Knowing how to extract and purify carbohydrates without artificially altering their oxygen isotope ratio (δ18O) is therefore essential.

We aimed to resolve the impact of different steps on sugars' δ18O values during their extraction and purification from leaf and phloem tissue. More precisely, we investigated (1) different drying processes (oven- vs freeze-drying), and (2) how extraction and purification affect leaf sugars. To clearly see fractionation and exchange processes, these experiments were performed using 18O-labelled water. We further examined (3) the influence of different EDTA media and immersion times to facilitate sugar exudation and subsequent yield from twig phloem tissue. Finally, we analysed (4) the sugar phloem composition, as well as the individual compounds’ carbon isotopic signatures (δ13C).

Comparison of freeze- and oven-dried sugars showed lower δ18O memory effects and more consistent oxygen isotopic signatures across different sugars, indicating lyophilisation as the more reliable method. The extraction and purification can be conducted without significant oxygen isotope fractionation. However, 18O-depletion was observed when sugars were dissolved and dried multiple times. This suggests that additional dissolution and drying steps should best be avoided whenever possible. Different immersion times and exudation media during twig phloem extraction revealed to have a substantial influence on the phloem sugars' overall oxygen isotopic signature, their composition, and the individual compounds' δ13C values.

Our research illustrates which precautions during sample preparation – from drying to extracting and purifying – need to be taken when plant sugars and their oxygen isotopic signature are of interest. Regarding the preservation of the phloem sugars' original δ18O values and stabilising their composition (prevention of sucrose degradation) as much as possible, we recommend a short immersion time of approx. 1 hour. After a thorough initial rinse of the tissue, the sap should be eluted in pure water without any additives (no EDTA). This further reduces the possibility of hexoses to exchange oxygen with that of the surrounding water.

How to cite: Egli, M., Lehmann, M. M., Brinkmann, N., Werner, R. A., Saurer, M., and Kahmen, A.: Testing different methods for the extraction and purification of leaf and phloem sugars for oxygen isotope analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22570, https://doi.org/10.5194/egusphere-egu2020-22570, 2020

D478 |
Ulrike Dusek, Roland Vernooij, Anupam Shaikat, Chenxi Qiu, Elena Popa, Patrik Winiger, Nick A. J. Schutgens, Peng Yao, and Guido R. van der Werf

Biomass burning on the African continent emits large amounts of CO2, CO, and aerosols. Our aim is to use measurements of the stable carbon isotope 13C in organic carbon, CO and CO2 in biomass burning smoke to estimate the contribution of C3 plants (trees and bushes) and C4 plants (mainly Savannah grass), which have very distinct 13C/12C ratios. This is possible, if 13C/12C ratios are not significantly altered by the combustion process. This assumption is investigated in a series of laboratory experiments, where C3 and C4 plants (corn and willow wood), or C3-C4 plant mixtures are burned. The laboratory results are used to interpret the results of pilot studies of smoke sampled in African savannah fires.


First results from the laboratory studies indicate that organic carbon (OC) from combustion of willow or corn shows 13C/12C ratios comparable to the burned plant material. For combustion of willow (C3), the 13C/12C ratios in OC tend to be slightly higher than in the wood fuel, depending on combustion conditions. For combustion of corn 13C/12C ratios of OC tend to be slightly lower than in the fuel. For mixtures of willow and corn the relationship between 13C/12C ratios in the emitted organic carbon and the fuel mixture is slightly non-linear: For a 50-50% oak wood and corn mixture the 13C/12C ratio in OC is closer to that of corn than that of willow. First results from pilot field studies indicate that a larger fraction of OC comes from trees and bushes, although mainly Savannah grass is burned in the investigated fires.

How to cite: Dusek, U., Vernooij, R., Shaikat, A., Qiu, C., Popa, E., Winiger, P., Schutgens, N. A. J., Yao, P., and van der Werf, G. R.: Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10484, https://doi.org/10.5194/egusphere-egu2020-10484, 2020

D479 |
Laurynas Bučinskas, Jonas Matijošius, and Andrius Garbaras

Excessive automotive engine exhaust emissions of gases and particulate matter (PM) pose a threat to public health and urban air quality. In an effort to reduce automotive emissions modern cars use a variety of engine modifications, catalytic systems and filters which in turn alter the isotope ratio of carbonaceous particles (isotope fractionation effect). Diesel engines are of particular interest due to higher production of particulates (soot) in comparison to gasoline engines [1].

The aim of this work was to examine particulate matter δ13C variation in automotive emissions using stable carbon isotope ratio measurements. Emission experiments were performed in dynamometer laboratory using four light passenger vehicles with differing liquid fuels - diesel, diesel with additives, 92 RON and 95 RON. Vehicles were tested with varying engine power and using simulated transient cycles in urban and rural areas. Engine exhaust particulate matter was collected on quartz filters. Later, isotope ratio δ13C values of fuel and exhaust carbonaceous particulates were measured using IRMS. δ13C values were then compared and level of isotope fractionation determined.

The obtained results show particulate matter δ13C values ranging from -28.8 ‰ to -27.2 ‰ during separate driving modes. Isotope fractionation Δ (particulates-fuel) values varied between 1.8 ‰ and 3.5 ‰. It was determined that δ13C values of automotive emissions depend on the type of fuel used, applied engine power, driving modes (urban, rural) and can be used to characterize automotive carbonaceous particle emissions.


[1]             M. V. Twigg, “Progress and future challenges in controlling automotive exhaust gas emissions,” Appl. Catal. B Environ., 2007.

How to cite: Bučinskas, L., Matijošius, J., and Garbaras, A.: Stable carbon δ13C analysis of automotive particulate matter emissions under controlled conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21320, https://doi.org/10.5194/egusphere-egu2020-21320, 2020

D480 |
Tamás Varga, László Haszpra, István Major, Eugan G. Nisbet, David Lowry, Rebecca E. Fisher, Timothy A.J. Jull, Mihály Molnár, and Elemér László

A three-year-long methane mole fraction and d13CCH4 measurement campaign was performed at the Hungarian tall tower station, Hegyhátsál, between 2013-2016. The results were compared with that of two NOAA atmospheric monitoring sites Mace Head and Zeppelin to determine the continental methane excess and the relative isotopic shift. The data then were used for bac trajectory analyses to identify potential methane source regions in Europe coupled with d13CCH4 results. The Hungarian station can be separated from the coastal and polar areas based on the mole fraction results having higher maxima and seasonal amplitude, but the d13CCH4 results match well with the NOAA stations’ results. Our study shows that although the local, regional anthropogenic and natural sources are major influences, more distant regions can also influence the measured CH4 level and d13CCH4 signal in the Pannonian Basin.

How to cite: Varga, T., Haszpra, L., Major, I., Nisbet, E. G., Lowry, D., Fisher, R. E., Jull, T. A. J., Molnár, M., and László, E.: Identification of potential methane source regions in Europe using d13C-CH4 measurements and back trajectory modeling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4529, https://doi.org/10.5194/egusphere-egu2020-4529, 2020

D481 |
| Highlight
Pauline Humez, Florian Osselin, Wolfram Kloppmann, Cynthia McClain, Michael Nightingale, and Bernhard Mayer

Due to concerns regarding potential impacts of the development of natural gas from unconventional hydrocarbon resources on groundwater systems in North America and elsewhere, it has been crucial to improve methods of Environmental Baseline Assessment (EBA). Any subsequent deviations from the EBA could indicate migration of natural gas into the monitored groundwater systems. In collaboration with Alberta Environment and Parks, over 800 groundwater samples have been collected from dedicated monitoring wells since 2006 resulting in an extensive high-quality database of aqueous and gaseous geochemical and isotopic compositions. Because methane is the main component of natural gas, it had been the principal target of our groundwater studies. Our objectives were a) to assess the occurrence of methane in groundwater throughout the province of Alberta (Canada), b) to use isotope techniques to track the predominant sources of methane, c) to use a combination of chemical and multi-isotopic techniques and models to assess the fate of methane in groundwater, and d) to use probability for predicting the presence of methane in groundwater based on hydrogeochemical parameters in regions where no gas data exist.

Methane was found to be ubiquitous in groundwater samples throughout the province of Alberta with concentrations varying from 2.9 10-4 to >2.4 mmol/l. The highest methane concentrations were found in Na-HCO3 and Na-Cl water-types where the sulfate concentrations were <1 mmol/l. Analyses of the isotopic compositions of sulfate, dissolved inorganic carbon (DIC) and methane revealed that in some groundwater systems bacterial sulfate reduction occurred (δ34SSO4 >+10‰ associated with lowest sulfate concentrations) and evidence for methane oxidation was also detected (highest δ13CCH4 values > ‑55‰ associated with lowest methane concentrations). Moreover, some δ13CDIC values were as high as +13.8‰ associated with the highest methane concentrations. A geochemical and multi-isotope model using long-term monitoring data was developed and revealed two different sources of methane: 1) microbial methane resulting from in-situ methanogenesis within the aquifer for a subset of the samples; 2) migration of microbial methane into aquifers characterized by various redox conditions, followed by methane oxidation potentially coupled with bacterial sulfate reduction within sulfate-rich zones causing a pseudo-thermogenic carbon isotopic fingerprint for the remaining methane. So far, no evidence of unambiguously thermogenic methane in the groundwater samples collected from dedicated monitoring wells has been found. Efforts to assess the probability of regional occurrence of methane in groundwater systems in Alberta have then focused on a model for methane prediction model based on logistic regression (LR) for regions of Alberta where no gas data exist. Using basic hydrogeochemical parameters such as occurrence of electron donors, well depth and total dissolved solids of groundwater, the LR approach shows excellent performance metrics e.g. model sensitivity, specificity >80% regarding the prediction of methane occurrence in groundwater of Alberta.

How to cite: Humez, P., Osselin, F., Kloppmann, W., McClain, C., Nightingale, M., and Mayer, B.: Sources, trends, and fate of methane in shallow aquifers of Alberta, Canada, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10777, https://doi.org/10.5194/egusphere-egu2020-10777, 2020

D482 |
Vilma Kangasaho, Aki Tsuruta, Tuula Aalto, Leif Backman, Sander Houweling, Maarten Krol, Wouter Peters, Ingrid Luijkx, Sebastian Lienert, Fortunat Joos, Edward Dlugokencky, Sylvia Michael, James White, and Rebecca Fisher

The atmospheric burden of methane (CH4) has more than doubled since the 18th Century. Currently the abundance of CH4 in the atmosphere is well known, but emission rates from different source sectors are uncertain. CH4 is emitted to the atmosphere from various sources. To better understand the changes in atmospheric CH4 abundance before and after 2006, it is important to study the contribution from these different sources separately. Most CH4 source have process specific δ13C-CH4 values, which can be used to broadly identify source sectors.

This study examines the seasonal cycle of atmospheric δ13C-CH4 in recent decades using the TM5 atmospheric transport. TM5 is driven by ECMWF ERA-Interim meteorological fields, and uses pre-calculated OH-fields and reaction rates with Cl and O(1D) to account for the CH4 sink processes in the atmosphere. TM5 is run at a 1ox1o resolution over Europe and globally at 6ox4o. Emissions for enteric fermentation and manure management, landfills and waste water treatment, rice cultivation, coal industry, oil and gas industry, and residential are taken from the EDGAR inventory. Natural emission for wetlands, peatlands and mineral soils, and soil sinks are taken from the LPX-Bern DYPTOP ecosystem model. Emissions for geological seeps including onshore hydrocarbon macro-seeps (including mud volcanoes), submarine (offshore) seeps, diffuse microseepage and geothermal manifestations are included. Emissions for fires (GFED v4), termites, wild animals and from the ocean are also included. Several sensitivity analyses are carried out. The sensitivity analyses include simulations with and without seasonal cycles in the anthropogenic emission fields (EDGAR v4.2 FT2010 vs EDGAR v4.3.2), and with and without spatial variations in source specific  δ13C-CH4 values, which are used to calculate 13CH4/CH4 emission ratios. The effect of including the seasonal cycle in the anthropogenic emissions were not significant, which means natural sources probably play more important role in determining the seasonal cycle of δ13C-CH4. The global observations of atmospheric CH4 and δ13C-CH4, provided by NOAA’s GMD, the INSTAAR and Royal Holloway, the University of London, are used for evaluation. We present the importance of having reasonable initial fields of atmospheric 13CH4, which will be later used as inputs for CarbonTracker Europe-δ13CH4 (CTE-δ13CH4) data assimilation system to optimise CH4 emissions by source category.

How to cite: Kangasaho, V., Tsuruta, A., Aalto, T., Backman, L., Houweling, S., Krol, M., Peters, W., Luijkx, I., Lienert, S., Joos, F., Dlugokencky, E., Michael, S., White, J., and Fisher, R.: Modelling the seasonal cycle of atmospheric δ13C-CH4 using source specific δ13C-CH4 values, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13274, https://doi.org/10.5194/egusphere-egu2020-13274, 2020

D483 |
Sebastian Lienert, Christoph Köstler, Sönke Zaehle, and Fortunat Joos

We investigate the seasonal cycle of δ13CO2 using the Earth system model of intermediate complexity Bern3D-LPX. Using a model of atmospheric transport (TM3), the spatial fields of simulated 13CO2 and CO2 exchange are translated to local δ13CO2 anomalies, which are then compared to atmospheric measurements. We discuss the ability of the model to accurately simulate the atmospheric seasonal δ13CO2 cycle, which could prove to be a valuable novel observational constraint. The coupled simulation allows us to distinguish the relative importance of the biosphere and ocean in determining the seasonal cycle of δ13CO2 at different measurement sites across the world.

The amplitude of the seasonal cycle of δ13CO2 is of particular importance to quantify land biosphere processes. The decreasing δ13CO2 of the atmosphere during the last decades (Suess effect) leads to a divergence of the δ13C signature in assimilation and heterotrophic respiration, because of the long lifetime of soil pools. This is expected to lead to a high sensitivity of the seasonal amplitude to the amount of soil respiration. The effect of changes in soil turnover times on the simulated seasonal cycle is explored with factorial simulations of the Dynamic Global Vegetation Model LPX-Bern.

How to cite: Lienert, S., Köstler, C., Zaehle, S., and Joos, F.: Simulating the seasonal cycle of 13C, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7841, https://doi.org/10.5194/egusphere-egu2020-7841, 2020

D484 |
Lisa Wingate, Clement Foucault, Nicolas Fanin, Joana Sauze, Pierre-Alain Maron, Virginie Nowak, Sebastian Terrat, Samuel Mondy, Evert van Schaik, Olivier Crouzet, Jérôme Ogée, and Steven Wohl

The stable oxygen isotope composition of atmospheric CO2 and the mixing ratio of carbonyl sulphide (COS) are potential tracers of biospheric CO2 fluxes at large scales. However, the use of these tracers hinges on our ability to understand and better predict the activity of the enzyme carbonic anhydrase (CA) in different soil microbial groups, including phototrophs. Because different classes of the CA family (α, β and γ) may have different affinities to CO2 and COS and their expression should also vary between different microbial groups, differences in the community structure could impact the ‘community-integrated’ CA activity differently for CO2 and COS. Four soils of different pH were incubated in the dark or with a diurnal cycle for forty days to vary the abundance of native phototrophs. Fluxes of CO2, CO18O and COS were measured to estimate CA activity alongside the abundance of bacteria, fungi and phototroph genes. The abundance of soil phototrophs increased most at higher soil pH. In the light, the strength of the soil CO2 sink and the CA-driven CO2-H2O isotopic exchange rates correlated with phototroph abundance. COS uptake rates were attributed to fungi whose abundance was positively enhanced in alkaline soils but only in the presence of increased phototrophs. In addition we developed a metabarcoding approach to reveal the interactions of specific taxonomic groups incuding photosynthetic eukaryotic algae and cyanobacteria when exposed to light and their impact on flux rates. Our findings demonstrate that soil-atmosphere CO2, COS and CO18O fluxes are strongly regulated by the microbial community structure in response to changes in soil pH and light availability and support the idea that different members of the microbial community express different classes of CA, with different affinities to CO2 and COS.

How to cite: Wingate, L., Foucault, C., Fanin, N., Sauze, J., Maron, P.-A., Nowak, V., Terrat, S., Mondy, S., van Schaik, E., Crouzet, O., Ogée, J., and Wohl, S.: The influence of light on soil community structure and consequences for soil CO2, CO18O and COS exchange , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20422, https://doi.org/10.5194/egusphere-egu2020-20422, 2020

D485 |
| Highlight
Sophie Baartman, Elena Popa, Maarten Krol, and Thomas Röckmann

Carbonyl sulfide (COS) is the most abundant sulfur-containing trace gas in the atmosphere, with an average mixing ratio of 500 parts per trillion (ppt). It has a relatively long lifetime of about 2 years, which permits it to travel into the stratosphere. There, it likely plays an important role in the formation of stratospheric sulfur aerosols (SSA), which have a cooling effect on the Earth’s climate. Furthermore, during photosynthetic uptake by plants, COS follows essentially the same pathway as CO2, and therefore COS could be used to estimate gross primary production (GPP). Unfortunately, significant uncertainties still exist in the sources, sinks and global cycling of COS, which need to be overcome. Isotopic measurements of COS could be a promising tool for constraining the COS budget, as well as for investigating its role in the formation of stratospheric sulfur aerosols.

Within the framework of the COS-OCS project, we developed a new pre-concentration and measurement system at Utrecht University, that can measure d33S and d34S from COS from 2 to 5 L air samples, with a current precision of about 5‰ and 2‰ for d33S and d34S, respectively. The aim of the project is to perform a global-scale characterization of COS isotopes by measuring seasonal, latitudinal and altitudinal variations in the troposphere and stratosphere. Here, I will present the details of the new measurement system and results from various atmospheric samples.

How to cite: Baartman, S., Popa, E., Krol, M., and Röckmann, T.: Isotopic Measurements: A New Tool for Studying Global Carbonyl Sulfide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3528, https://doi.org/10.5194/egusphere-egu2020-3528, 2020

How to cite: Baartman, S., Popa, E., Krol, M., and Röckmann, T.: Isotopic Measurements: A New Tool for Studying Global Carbonyl Sulfide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3528, https://doi.org/10.5194/egusphere-egu2020-3528, 2020

How to cite: Baartman, S., Popa, E., Krol, M., and Röckmann, T.: Isotopic Measurements: A New Tool for Studying Global Carbonyl Sulfide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3528, https://doi.org/10.5194/egusphere-egu2020-3528, 2020

D486 |
Alexander Knohl, Jan Muhr, M. Julian Deventer, Emanuel Blei, Jelka Braden-Behrens, Edgar Tunsch, Mattia Bonazza, Penelope A. Pickers, David Nelson, Mark Zahniser, and Andrew C. Manning

Ecosystem assimilation and respiration result in anti-correlated fluxes of oxygen (O2) and carbon dioxide (CO2). While the ecosystem O2:CO2 molar exchange ratio is usually assumed constant at ≈1.1 on longer timescales, variations for individual ecosystem compartments or shorter timescales have been reported in the past. We hypothesize that these exchange ratio variations can reveal information about underlying biotic and abiotic processes in plants or soil that cannot be inferred from traditional net ecosystem exchange measurements. To date, oxygen measurements have not been widely implemented in ecosystem research due to the technical challenge of detecting very small variations (ppm-level) against an atmospheric background of ≈21% (≈210,000 ppm).

We evaluate the performance and applicability of two commercial oxygen analyzers Integrated into custom-built gas handling and calibration systems, and report first results from measurements of O2:CO2 exchange ratios in a managed European beech forest in central Germany.

System 1, consisting of a relatively slow response differential fuel cell O2 analyzer (Oxzilla FC-2, Sable Systems Inc., USA) together with a non-dispersive infrared CO2 analyzer (LI-840, LI-COR Biosciences, USA), was used to simultaneously measure O2 and CO2 mole fractions in air sampled from soil, stem, and branch chambers. Chambers were operated in an open flow-through steady-state design aimed at equilibrium mole fractions within a few hundred ppm of atmospheric background. Using a multiplexer valve design, we measured chambers sequentially by directing chamber air at a controlled flow rate to the gas analyzing system.

Preliminary analysis of August to December 2018 data show that chamber-based flux estimates for O2 and CO2 were anti-correlated at all times, and that the O2:CO2 molar exchange ratios (defined as ‑Δ[O2]/Δ[CO2]) varied considerably over time and between the different ecosystem compartments (soil, stems, and branches) with a median (interquartile range) of 0.94 (0.75 to 1.09).

In system 2, CO2, O2 and water vapor (H2O) measurements were performed with a fast response (5 Hz) gas analyzer using tunable infrared laser direct absorption spectroscopy (TILDAS, Aerodyne Research Inc., USA). We measured fluctuations in O2:CO2 exchange ratios in air sampled at 1.5 times the canopy height, i.e. a typical eddy covariance set-up.

Analysis of the high-frequency data revealed instrumental noise levels of ≈±12 ppm O2. Fourier transformation of high-frequency data obtained during well-mixed boundary layer conditions indicate that turbulent fluctuations of the O2 signal were insufficiently resolved when compared to the CO2 power spectra. When averaging high-frequency data to 2-min aggregates, instrumental noise was reduced to ≈±1 ppm, similar to the precision of system 1. At this timescale, contemporaneous measurements of above-canopy air revealed agreement between the fuel cell and the laser systems, both in O2 mole fraction (R2 = 0.6 slope = 0.7, MAE = 1.6 ppm) and in estimated O2:CO2 exchange ratios of 1.01 and 0.97 for system 1 and 2, respectively.

Our presentation will expand on the applicability of both O2 and CO2 measurement systems with regard to micrometeorological flux techniques. Specifically, we elucidate on the potential of using O2 flux measurements as a constraint for estimating ecosystem-scale gross primary production.

How to cite: Knohl, A., Muhr, J., Deventer, M. J., Blei, E., Braden-Behrens, J., Tunsch, E., Bonazza, M., Pickers, P. A., Nelson, D., Zahniser, M., and Manning, A. C.: Measuring oxygen fluxes in a European beech forest - results from the OXYFLUX project, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18822, https://doi.org/10.5194/egusphere-egu2020-18822, 2020

D487 |
Amzad Laskar, Rahul Peethambaran, Sergey Gromov, Thomas Blunier, and Thomas Roeckmann

Abundances of 17O18O and 18O18O (also called clumped isotopes and denoted by Δ35 and Δ36) of O2  in firn and ice core air are novel tracers that can be useful to study past changes in atmospheric photochemistry and temperature. We present Δ35 and Δ36 values measured in firn and ice core air O2 from North Greenland (NEEM; 77.45°N 51.06°W). The aim is to reconstruct the preindustrial-industrial, Holocene and glacial-interglacial variation in the tropospheric ozone photochemistry and temperature. Measurements of Δ35 and Δ36 are carried out using a high-resolution stable isotope ratio mass spectrometer Thermo Fisher 253 ULTRA[1]. Our measurements of Δ35 and Δ36  across past air, from archive samples, to the modern-day show significant changes in the atmospheric photochemistry via ozone burdening and stratospheric- tropospheric transport processes. We will present the measurement results along with a detailed discussion on the dominant process using explicit dynamic simulations of ∆36 in the AC-GCM EMAC model [2,3,4].


How to cite: Laskar, A., Peethambaran, R., Gromov, S., Blunier, T., and Roeckmann, T.: 17O18O and 18O18O in ice core O2 from Greenland: implications to reconstruct past atmospheric photochemistry , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20741, https://doi.org/10.5194/egusphere-egu2020-20741, 2020

D488 |
Anna Pierchala, Kazimierz Rozanski, Marek Dulinski, Zbigniew Gorczyca, and Robert Czub

Stable isotopes of hydrogen and oxygen (2H and 18O) are often used for quantification of water budgets of lakes and other surface water bodies, in particular for the assessment of underground components of those budgets [1]. Recent advances in laser spectroscopy enabled simultaneous analyses of 2H, 18O and 17O content in water, with measurement uncertainties comparable (δ18O) or surpassing (δ2H) those routinely achieved by off-line sample preparation methods combined with conventional IRMS technique [2]. This open up the doors for improving reliability of isotope-aided budgets of surface water bodies by adding third isotope tracer (17O). This, however, requires adequate information on triple isotope effects accompanying evaporation of water, in particular the kinetic isotope effect related to evaporation of 1H217O isotopologue.

Here we present the results of dedicated laboratory experiments aimed at quantification of triple isotope effects accompanying evaporation of water under fully developed diffusive sublayer [3]. Identical containers with predefined mass of water of known isotopic composition were placed in an isolated chamber with controlled atmosphere during the experiment (temperature, relative humidity). The chamber was flushed with synthetic air. At regular time intervals (approximately one week) containers were removed one by one from the chamber, the remaining mass of water in the removed container was determined gravimetrically, and stored for subsequent isotope analyses. The flow rate was adjusted at each step of the process to keep humidity inside the chamber constant. Evaporation continued until approximately half of the initial mass of water was removed from the containers. The experiment was repeated under diiferent conditions inside the chamber (two different temperatures and three different values of relative humidty).

The results of the experiments were interpreted in the framework of Craig-Gordon model of evaporation [3]. It turned out that the assumption often used in the description of isotopic effects accompanying evaporation that liquid phase is isotopically homogeneous during the process, leads to conflicting results for three isotope systems in use. However, if surface enrichment of the liquid phase, different for each heavy isotopologue (1H2H16O, 1H218O, 1H217O) is included in the model, consistent results for all three isotopes can be achieved, with calculated kinetic fractionation factor for 1H217O isotopologue equal 14.76 ± 0.48 ‰,. This value agrees, within the quoted uncertainty, with the value of 14.60 ± 0.30 ‰ obtained by Barkan and Luz [4].  

Acknowledgements: The presented work was supported by National Science Centre (research grant No. 2016/23/B/ST10/00909) and by the Ministry of Science and Higher Education (project no. B02)

[1]   Rozanski K. Froehlich K. Mook WG. Technical Documents in Hydrology, No. 39, Vol. III, UNESCO, Paris, 2001 117 pp.
[2]   Pierchala A, Rozanski K, Dulinski M, Gorczyca Z, Marzec M, Czub R, Isotopes in Environmental and Health Studies, 2019 (55) 290-307.
[3]   Horita, J. Rozanski K. Cohen S. 2007. Isotopes in Environmental and Health Studies, 2007 (44) 23-49.
[4]   Barkan E. Luz B. Rapid Commun. Mass Spectrom., 2007(21) 2999-3005.

How to cite: Pierchala, A., Rozanski, K., Dulinski, M., Gorczyca, Z., and Czub, R.: Triple isotope effects accompanying evaporation of water: new insights from laboratory experiments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6708, https://doi.org/10.5194/egusphere-egu2020-6708, 2020

D489 |
Mauro Masiol, Daniele Zannoni, Barbara Stenni, Giuliano Dreossi, Luca Zini, Chiara Calligaris, Daniele Karlicek, Marzia Michelini, Onelio Flora, Franco Cucchi, and Francesco Treu

Stable water isotopes are widely-used tracers to investigate hydrological processes occurring in the atmosphere and to determine the geospatial origin of water, i.e. to acquire useful information about the hydrological cycles over catchment basins and to find the origin of water recharging rivers, aquifers, and springs. Mapping the isotopic composition of precipitation provides hydrological and climate information at regional and global scales. However, the isotopic composition of precipitation is usually analyzed at large scales with a limited spatial resolution. In Italy, a few studies mapped the oxygen stable isotopes using annually-averaged data, not accounting for the strong seasonality of the isotopic composition linked to climatic and weather factors. To partially fill this gap, the present study proposes a detailed analysis of more than 2250 isotope data (δ18O, δ2H, and deuterium excess) related to precipitations collected in the Friuli Venezia Giulia (FVG) region (Italy) with monthly or seasonal frequency in 36 sites between 1984 and 2015.

The FVG region lies at the north-eastern end of Italy, bordering Austria in the North and Slovenia in the East, and extends over ~7.9·103 km2. From a hydrogeological point of view, FVG is an interesting case study. Large highly-permeable carbonate aquifers are present in the Alps and Prealps, while the southern part of the region is characterized by an alluvial plain, split by the spring belt into two sectors: the High Plain in the North, characterized by an highly-permeable unconfined aquifer, and the Low Plain in the South, characterized by a system of confined and artesian aquifers. All the aquifers are recharged by the effective precipitations which in the FVG exhibits among the highest annual precipitation rates in Italy (with peaks >3000 mm/year).

For the present research, the isotopic data were used: (i) to analyze the spatial and seasonal variability of isotopic composition; (ii) to relate water isotopes with orography and weather parameters collected from meteorological stations as well as using ECMWF ERA5 reanalysis; (iii) to reconstruct the local meteoric water lines across the FVG at annual and seasonal bases; (iv) to quantify interannual trends and analyze their spatial distribution; and (iv) to model the spatial distribution of isotope content in precipitation and create annual and seasonal maps.

How to cite: Masiol, M., Zannoni, D., Stenni, B., Dreossi, G., Zini, L., Calligaris, C., Karlicek, D., Michelini, M., Flora, O., Cucchi, F., and Treu, F.: Interannual analysis of high spatially-resolved δ18O and δ2H data in precipitation across North-East Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8881, https://doi.org/10.5194/egusphere-egu2020-8881, 2020