The introduction of widely available optical isotopic ratio spectroscopy (OIRS) has enabled in-field measurements of isotopologues of carbon dioxide and methane (CO₂ and CH₄), allowing the source apportionment of greenhouse gases through distinguishing between natural and anthropogenic emissions of CO₂ and CH₄. At present, there are no existing internationally accepted reference materials which provide traceability for the calibration of δ¹³C-CO₂, δ¹³C-CH₄, δ²H-CH₄ and δ¹⁸O-CO₂ OIRS measurements which meet the World Metrological Organisation’s data compatibility goals to underpin global measurements.

We present the latest progress achieved during the EMPIR project Stable Isotope Metrology to Enable Climate Action and Regulation (STELLAR), on the development of primary reference materials (PRMs) which are traceable to the SI for amount fraction and existing isotope ratio scales. The production and certification of pure and ambient amount fraction reference materials is discussed alongside the sensitivities of the production and sampling process to isotopic fractionation. Methodologies for mitigating fractionation during PRM production and sampling will be outlined.

The production of the air matrix and the effects of trace gases and water vapour in the air matrix on the isotope ratio of the ambient PRMs is presented. The effects of trace gases in the matrix on the measurement of the isotope ratio of the ambient amount fraction CO₂ and CH₄ PRMs is also discussed for OIRS techniques.

We demonstrate achievement of the targeted uncertainties in δ¹³C_VPDB-CO₂ of ± 0.1 ‰ and ± 0.5 ‰ for δ¹⁸O_VPDB-CO₂. Uncertainty budgets are presented and the main contributions to the uncertainty budget are highlighted. The stability of the isotope ratio of the PRMs with pressure and time (2 years) is also discussed alongside comparisons with existing scales for amount fraction.

How to cite: Hill-Pearce, R., Mussell-Webber, E., Hillier, A., and Brewer, P.: Meeting the demand for δ13C-CO2, δ18O-CO2, δ13C-CH4 and δ2H-CH4 Reference Materials for Climate Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18482, https://doi.org/10.5194/egusphere-egu24-18482, 2024.

The commercial development of laser-based instruments over the last decade that can measure real-time isotopic ratio variations of greenhouse gases, and notably CO₂, has allowed their application across a wide range of scientific and technical disciplines. Precise measurements can be achieved, and appropriate calibration strategies [1] and standards need to be applied to achieve accurate results and consistency with traditional mass spectrometric measurement methods. For CO₂, calibration strategies can be based on using CO₂ in air standards with the same isotopic ratios but containing different amount fractions, or the same amount fraction and different isotope ratios. This has resulted in the availability of calibration standards containing different isotope ratios at different amount fractions, which may or may not contain nitrous oxide. An international comparison programme at the BIPM (BIPM.QM-K4) is in development to demonstrate the equivalence of such standards, which would allow them to be used interchangeably by operators.

The BIPM’s comparison facility is based on a dual inlet isotope ratio mass spectrometer with a custom built (BIPM) Air Trapping system (BAT) to extract CO₂ from air mixtures using cryogenic separation for determination of δ¹³Cand δ¹⁸O-CO_2, with a correction for the N₂O present in the sample. A procedure for regularly determining the relative ionization efficiency of N₂O in relation to CO₂ has been developed and is applied as a function of the amount fraction of N₂O in the sample. Metrological traceability is achieved through a hierarchy of low-pressure CO₂ standards with δ¹³C values nominally at -1 ‰, -35 ‰ and -43 ‰, calibrated on the VPDB scale via IAEA 603 carbonate standard material. Initial validation of the performance of the facility has been performed with the extraction of CO₂ from gas mixtures within the range of 380 μmol mol⁻¹ to 800 μmol mol⁻¹ and δ¹³C and δ¹⁸O-CO₂ values from 1 ‰ to -43 ‰ and -7 ‰  to -35 ‰, respectively. The method demonstrates excellent reproducibility, with standard deviations of 0.005% and 0.05%. for δ¹³C  and δ¹⁸O-CO₂, respectively. In addition, the robustness of the N₂O correction has been demonstrated by comparing δ¹³C  and δ¹⁸O-CO₂ values from standards produced from the same CO₂ source gas but at differing amount fractions. The performance and validation of the facility will be described.

[1] Flores, E., Viallon, J., Moussay, P., Griffith, D. W. T. & Wielgosz, R. I. Calibration strategies for FT-IR and other isotope ratio infrared spectrometer instruments for accurate δ¹³C and δ¹⁸O measurements of CO₂ in air. Anal. Chem. 89, 3648–3655 (2017).

How to cite: Flores, E., Choteau, T., Moussay, P., Eun, H. J., Allison, C., and Wielgosz, R. I.: A reference facility for the comparison of CO2 in Air isotope ratio standards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2091, https://doi.org/10.5194/egusphere-egu24-2091, 2024.

Isotope ratio is a powerful tool for discriminating between sources and sinks of greenhouse gases, enabling their source apportionment. We have produced the first high volume and high-pressure methane (CH₄) gas reference materials with a certified δ¹³C-CH₄ and δ²H-CH₄ in a synthetic air matrix. This matrix contained ambient amount fractions of the major air components and key greenhouse gases CO₂ and N₂O.

The SI traceable methane in air reference materials were gravimetrically produced in 10 L cylinders at a pressure of 100 bar to fulfil the high-volume calibration requirements of optical isotope ratio spectroscopy (OIRS) techniques. The methane sources were chosen to span the observed atmospheric δ¹³C-CH₄ and will be used to monitor the isotope ratio of atmospheric methane at sites across Europe.

The δ¹³C-CH₄ and δ²H-CH₄ of pure methane sources and diluted methane references were measured via isotope ratio mass spectrometry (IRMS). The diluted methane reference materials were used to characterise an OIRS (Aerodyne Research Inc.) analyser fitted with an in-house built pre-concentrator. Further methane sources were characterised for δ¹³C-CH₄ and δ²H-CH₄ after dilution on the calibrated Aerodyne to create a suite of reference materials with δ¹³C-CH₄ values spanning -51.94 to -39.19 ‰ and -202.56 to – 182.04 ‰ for δ²H-CH₄.

Uncertainty budgets for the diluted reference materials will be presented with gravimetric amount fraction uncertainties aiming towards the World Metrological Organization Global Atmosphere Watch (WMO-GAW) compatibility goal of 2 nmol mol^-1 across the amount fraction range of 1.75-2.10 µmol mol^-1. Reference materials were produced at a range of amount fractions (1.7 to 569 µmol mol^-1) required to calibrate different OIRS techniques. Commonly interfering matrix components Ar, O₂, CO₂ and N₂O were added at ambient amount fractions (420 µmol mol^-1 and 335 nmol mol^-1 for CO­₂ and N₂O respectively). Approximately 30 reference materials, each containing around 1000 litres of gas were distributed to seven partners in the EMPIR Metrology for European emissions verification on methane isotopes (isoMET) project. Measurements using these reference materials will enable comparability of isotopic methane data collected as part of national and international monitoring networks.

How to cite: Hopkinson, E., Safi, E., Rennick, C., Hillier, A., Mussell-Webber, E., Moossen, H., Wilson, F., Hill-Pearce, R., Worton, D., Brewer, P., and Arnold, T.: First Synthetic Isotopic Methane Gas Reference Materials for Optical Isotope Ratio Spectroscopy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17994, https://doi.org/10.5194/egusphere-egu24-17994, 2024.

How to cite: Safi, E., Rennick, C., Forster, G., O'Doherty, S., Pitt, J., Mussell-Webber, E., Hill-Pearce, R., Hillier, A., Worton, D., Brewer, P., Charoenpornpukdee, K., and Arnold, T.: Intercomparison of greenhouse gas measurements using whole air and synthetic standards at UK tall tower sites , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19027, https://doi.org/10.5194/egusphere-egu24-19027, 2024.

The main goal of ICOS Hungary was to expand the geographical coverage of the ICOS network towards Eastern Europe. As Hungary is located in the zone of westerlies winds in Europe, adding measurement stations East of the existing ICOS network may significantly reduce the uncertainty of the continental atmospheric CO2 and CH4 budget models. Since the joining of HUN it is (almost) the easternmost ICOS atmospheric background station.

ICOS has high expectations for all the stations seeking to join the observation system. These expectations include ensuring the highest quality and employing state-of-the-art equipment available in the stations. Atmospheric stations wishing to connect to the network has to develop their gas handling systems themselves. This requirement places additional responsibility on the operators of stations to create their own systems, allowing them to tailor gas handling processes to their unique needs and in accordance with ICOS network specifications.

The gas handling system for the HUN station, was built in the collaboration between ATOMKI and Isotoptech Zrt., that has been developed for the possibility of commercial use also. This developed system has been operational in Hegyhatsal since the spring of 2022. The core of the system's is a Picarro analyzer (CO2, CH4 and H2O), that requires properly filtered and semidried air for operation. According to the expectations, the developed system meets all the ICOS requirements, including minimized response time, addressing memory effects, and ensuring appropriate flushing capacity. It operates in five independent sampling height (at HUN connected to elevations at 115m, 82m, 50m, 10m and a spare one) with a sampling rate of 10 l/min. Each line uses 2-micron filters before the Picarro, and one multiport VALCO rotary valve runs for efficient and precise environmental GHG gas analysis. For the purpose of ensuring analytical security, high-performance KNF inert pumps are employed for sample transfer/flushing in order to maintain the integrity and reliability of the analytical process.

From 2022 the monitoring station continuously measures atmospheric concentrations of CO₂, CH₄, and other trace gases at the four sampling levels.

The entire novel, compact gas handling equipment (made by Isotoptech) has stand-alone design, with a footprint of less than 1 m², 2 m height, integrates all the components, and is designed for easy mobility. The gas handling system has undergone one year of routine operation with minimal maintenance requirements, proving to be reliable and consistently operational even while it is managed remotely from a distance of 500 km, without significant disruptions.

Prepared with the professional support of the Doctoral Student Scholarship Program of the Cooperative Doctoral Program of the Ministry of Innovation and Technology financed from the National Research, Development and Innovation Fund and supported by the PARIS project (Grant Agreement No. 820846), which is funded by the European Commission through the Horizon 2020 research programme.

How to cite: Molnar, M., Barath, B. A., Varga, T., Major, I., Ban, S., and Haszpra, L.: Novel, optimized and compact gas handling system for the HUN tall tower ICOS station, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19252, https://doi.org/10.5194/egusphere-egu24-19252, 2024.

In recent years, the field of laser spectroscopy has witnessed significant progress, leading to major advancements in the detection of atmospheric trace gases. This technological evolution is reflected in a growing number of commercial implementations, especially for prevalent atmospheric gases, such as carbon dioxide (CO₂) and methane (CH₄). The spectrum of detectable trace gases continues to expand, and manufacturers offer instruments with increasing performance in term of selectivity, sensitivity, power consumption, compactness and cost-effectiveness.

In this presentation, we focus on recent instruments for the observation of atmospheric nitrous oxide (N₂O). N₂O is a major long-lived greenhouse gas which plays an important role in stratospheric ozone depletion, but still suffers from inadequate global data coverage. Therefore, the advent of more economical yet resilient instruments, demanding less space and power compared to conventional models, presents a welcome opportunity to broaden the N₂O monitoring network.

We provide an overview of laboratory tests carried out at Empa on a variety of commercial models. The evaluated techniques include (i) Mid-IR Tunable Diode Laser Spectrometry (TDLAS) with Interband Cascade Lasers (ICLs) and Quantum Cascade Lasers (QCL), (ii) Optical Feedback – Cavity Enhanced Absorption Spectroscopy (OF-CEAS), (iii) Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS), and (iv) Cavity Ringdown Spectroscopy (CRDS).

The tests assessed the suitability of the instruments for precise atmospheric N₂O monitoring and provide insights into the operation, data handling and quality assurance / quality control procedures required for long-term operation. Particular attention was paid to the evaluation of the short-term precision and stability of the instrument response and the repeatability within days to weeks.

Overall, the instrument performance is still superior for the most-established CRDS and OA-ICOS analyzers, which are widely used in the Global Atmosphere Watch (GAW) programme and the European Integrated Carbon Observation System Research Infrastructure (ICOS-RI). Nevertheless, the latest generation of TDLS and OF-CEAS instruments are cost-efficient alternatives, which may be suited for more extensive networks, such as the ones to be designed under the umbrella of World Meteorological Organization's new Global Greenhouse Gas Watch (G3W) programme. However, great care needs to be taken in terms of quality assurance and quality control (QA/QC) to ensure long-term accuracy and traceability. The most cost-efficient instrumental components still need to be identified as a function of the scientific targets and the related network design.

How to cite: Emmenegger, L., Zellweger, C., and Steinbacher, M.: Assessment of spectroscopic instruments for continuous atmospheric nitrous oxide monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6528, https://doi.org/10.5194/egusphere-egu24-6528, 2024.

Agricultural processes are the main source of ammonia emissions, and they are a significant source of methane emissions. For quantification of emissions from livestock animal housings onsite measurements for these gases are needed in parallel with certified reference standards that enable SI-traceability of the measurement results. We have developed dynamic reference gas generation method that is suitable for onsite use when calibrating the analysers and sensors applied either inside or outside the animal housings, for determination of ammonia concentrations in large enough concentration range spanning several orders of magnitude. In combination with static reference gas mixtures for greenhouse gases that are measured in parallel with ammonia, this method is used to calibrate and validate measurements of these most important molecular emissions from agriculture. We present the results of application of this methodology onsite for calibration of different types of sensors and analysers that provide the primary concentration data used in calculations sourcing data for corresponding emissions inventory reports.

How to cite: Rajamäki, T.: Traceable onsite measurement of ammonia and greenhouse gas emissions from livestock production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12088, https://doi.org/10.5194/egusphere-egu24-12088, 2024.

To incorporate Equivalent Black Carbon (eBC) as a new variable in air quality (AQ) guidelines and to develop effective mitigation strategies, it is crucial to estimate its mass concentration consistently throughout the AQ monitoring networks (AQMNs) with minimal uncertainties. A reliable determination of eBC mass concentrations derived from filter absorption photometers (FAPs) measurements depends on the appropriate quantification of the mass absorption cross-section (MAC) for converting the absorption coefficient (b_abs) determined from FAPs measurements to eBC. Several studies have shown substantial variability in MAC due to local and regional variability in e.g., eBC sources, burning conditions, and eBC internal mixing among others. This MAC variability may lead to considerable uncertainty in eBC estimation. This study investigates the spatial-temporal variability of the MAC obtained from simultaneous elemental carbon (EC) measurements and b_abs determination performed following the ACTRIS procedures at 22 sites. We compared different methodologies for retrieving eBC integrating different options for calculating MAC, including locally derived MAC, median MAC value calculated from 22 sites, and site-specific rolling regression MAC. The eBC concentrations that underwent corrections using these methods were identified as MeBC (median MAC), LeBC (local MAC), and ReBC (Rolling MAC) respectively. These corrected eBC concentrations were compared with eBC as directly provided by FAPs (NeBC; nominal instrumental MAC). The median MAC values were 7.8 ± 3.4 m² g⁻¹ from 12 aethalometers at 880 nm, and 10.6 ± 4.7 m² g⁻¹ from 10 MAAPs at 637 nm. Combining datasets obtained from these two types of FAPs resulted in a median value of about 10.7 ± 4.8 m² g⁻¹ at 637 nm. However, the experimental MAC values showed significant site and seasonal dependencies, with heterogeneous patterns between summer and winter in different regions. Pronounced differences (up to more than 50%) were observed between NeBC from FAPs and ReBC due to the differences observed between the experimental and nominal MAC values. Moreover, long-term trend analysis revealed a statistically significant (s.s.) decreasing trend in EC mass concentrations. Interestingly, we show that the corresponding corrected eBC trends are not independent of the way eBC is calculated, due to the variability of MAC. NeBC and EC decreasing trends were consistent at sites with no significant trend in experimental MAC. Conversely, where MAC showed a s.s. trend, the NeBC and EC trends were not consistent while ReBC concentration followed the same pattern as EC. These results underscore the importance of accounting for MAC variations when deriving eBC measurements from FAPs and emphasize the necessity of incorporating EC observations to constrain the uncertainty associated with eBC. Thus, this study recommends the use of co-located measurements of b_abs and EC mass concentrations by expanding monitoring networks to include regular EC sampling. However, in situations where EC observations are unavailable, we recommend applying the default MAC value of around 10 m² g⁻¹ recommended by ACTRIS when b_abs is provided by MAAP at 637 nm and the MAC value of 7.8 m² g⁻¹ when b_abs is provided by aethalometers at 880 nm.

How to cite: Savadkoohi, M., Pandolfi, M., Alastuey, A., and Querol, X.: Recommendations for reporting equivalent Black Carbon (eBC) concentration based on long-term pan-European in-situ observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10485, https://doi.org/10.5194/egusphere-egu24-10485, 2024.

The Proton-transfer-reaction mass spectrometer (PTR-MS) has become an important tool for real-time monitoring of volatile organic compounds (VOCs) in the atmosphere. PTR-MS is semi-quantitative in untargeted analysis if the transmission of the analytes is well constrained. The transmission at different m/z is determined by using commercial calibration standards.

We present an additional method to constrain the instrument transmission using well-monitored ozone-depleting substances in the atmosphere. Ozone-depleting substances such as chlorofluorcarbons (CFCs)  are banned and monitored through the Montreal Protocol, but their concentration in the atmosphere is relatively stable, and due to their long lifetime they are well mixed. Two of these banned substances can be detected using PTR-MS, namely Trifchloroluoromethane (CFC-11) and carbon tetrachloride (CCl₄). Their major ion CCl₃⁺ is measured at m/z 116.906. A clear signal at this mass is observed in all atmospheric measurements. Since the concentrations of CFC-11 and CCl₄ in the atmosphere are measured frequently by global monitoring networks, they can be used to determine the transmission at m/z 116.906. We experimentally determined the pseudo-reaction rate constants of CFC-11 and CCl₄. Utilizing this, the transmission of m/z 116.906 can be determined using any atmospheric measurements in the past or present. This innovative approach can be a useful tool for quality control of PTR-MS data and checking instrument performance during measurements.

How to cite: Holzinger, R. and Notø, H. Ø.: CFC-11 and CCl4 in the Atmosphere: A free calibration standard for Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17820, https://doi.org/10.5194/egusphere-egu24-17820, 2024.

A current bottleneck in accurately predicting the impacts of urban emissions on secondary pollution, including ozone and secondary organic aerosol, is the quantification of oxygenated volatile organic compounds (OVOCs). In this work, a voltage scanning (VS) method for quantifying OVOCs, utilizing collision-induced dissociation, is developed using the VOCUS chemical ionization mass spectrometer operated with ammonium as reagent ions. The method is optimized in laboratory studies and tested in the most challenging environment aboard a scientific aircraft during the AEROMMA 2023 campaign to quantify OVOCs in plumes over the Chicago metropolitan area. Voltage scans are optimized to produce for the first-time outcomes down to within a 5-second time resolution. Several OVOCs are quantified that originate from unconventional emerging pollution sources in urban air including cooking and daily household chemicals, in particular solvents and fragrances. Furthermore, the VS method is used to successfully quantify oxidation products within these emissions, notably organic nitrates, traditionally difficult to calibrate. Importantly, we determine the sensitivity of a prevalent organic nitrate in urban air, laying the foundation for refining chemical transport models. This study therefore demonstrates the voltage scanning method’s versatility and effectiveness in quantifying complex compounds during field measurements, particularly in urban environments.

Figure 1: In the left time series of C₆H₆O₂ ionized by NH₄⁺, the data points used for the VS (Voltage Scanning) fitting are indicated. The ∆E⁵⁰_kin results for the respective VS data section are displayed on the second y-axis. ∆E⁵⁰_kin is the kinetic energy of the cluster at half signal strength derived from a VS measurement, where an increase in electric field strength in a scanning region results in a reduction of signal due to collision induced dissociation. The size and opacity of the ∆E⁵⁰_kin markers are adjusted based on the r² of the fit, with the number of the VS labeled in circles for easier identification. The Violin plot on the right illustrates the sensitivities corresponding to these ∆E⁵⁰_kin values together with the measured sensitivity to Ethylene Glycol in the lab (orange). In the violin plot, the median and values for the upper and lower quartiles are presented.

How to cite: Roska, M., Stockwell, C., Xu, L., Coggon, M. M., Bates, K., Warneke, C., and Gkatzelis, G. I.: Quantification of Oxygenated Volatile Organic Compounds using Collision-Induced-Dissociation during the AEROMMA Campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20676, https://doi.org/10.5194/egusphere-egu24-20676, 2024.

Many halogenated volatile organic compounds (VOCs) are found in the atmosphere in the pmol/mol range. These halogenated VOCs have negative impacts on the environment as they are strong greenhouse gases and/or contribute to the depletion of the stratospheric ozone layer or their degradation products may have a negative impact on the environment. This underpins the importance to accurately measure the amount fractions of these substances in the atmosphere on the long-term.
The Global Atmosphere Watch (GAW) Programme of the World Meteorological Organization (WMO) is a long-term international global programme that coordinates observations and analysis of atmospheric composition changes. The GAW Programme is a collaboration of more than 100 countries and it relies fundamentally on the contributions of its members to help to build a single, coordinated global understanding of atmospheric composition and its change. For most substances there is a Central Calibration Laboratory (CCL) that is responsible for maintaining and distributing the WMO references for instrument calibration for a specified gas in air. However, until summer 2023 there was no CCL for halogenated VOCs. METAS applied successfully for the CCL function for a total of ten halogenated VOCs because METAS' gas analysis laboratory has a decade of experience in the production of reference gas mixtures for halogenated VOCs. Here, we will present our new function as CCL including our services, the work done in the past and the planned work for the next years.

How to cite: Bühlmann, T. and Roos, D.: METAS: the new WMO-GAW Central Calibration Laboratory for halogenated VOCs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2131, https://doi.org/10.5194/egusphere-egu24-2131, 2024.

The monitoring of the increasing levels of CO₂ in atmosphere, together with the discrimination between the natural and anthropogenic sources of CO₂, is of utmost importance to support climate change studies and the reduction of the CO₂ emissions from human activities in the close future. The involvement of the metrological community is essential to achieve the comparability of results over space and time, to assure accuracy and metrological traceability, linking all the individual measurement results to common and stable reference standards.

The availability of sound and affordable reference materials for the measurement of the isotopic composition of CO₂ at ambient amount fraction is foreseen to support the researchers operating in the isotope measurement field, by means of spectroscopic techniques, to assure the metrological traceability for the determination of the isotopic composition of CO₂ in air. Reference gas mixtures at known isotopic composition produced by means of primary methods, such as gravimetry, represent a good opportunity for this purpose.

At INRiM, the Italian National Metrology Institute, the realization of gaseous reference materials of CO₂ in air at known δ¹³C-CO₂ started within the European Joint Research Project (JRP) 16ENV06 SIRS, and continued with the JRP 19ENV05 STELLAR.

The reference mixtures are realized by the gravimetric method, following the ISO standard 6142-1, in high-pressure cylinders of aluminum alloy, obtaining low preparation uncertainties of 0.33 % for the CO₂ amount fraction at atmospheric level. These mixtures are prepared from parent mixtures at higher amount fraction, realized at INRiM from different pure CO₂ sources.

Non Dispersive Infrared Spectroscopy (NDIR ABB URAS 14, Switzerland) is used to verify the mixtures for their amount fraction values while Fourier Transform Infrared Spectroscopy (FTIR Thermo Scientific Nicolet iS50, USA) is used for the δ¹³C-CO₂ value assignment. The δ¹³C-CO₂ values of the gravimetric mixtures span in the range from +1.3 ‰ to -42 ‰.

Recently, a Cavity Ring-Down Spectrometer (CRDS G2131i Picarro, USA) was acquired to double-check the isotopic composition of the prepared mixtures. Preliminary tests were carried out for the metrological characterization of the instrument, followed by the set-up of the analytical methodology for the confirmation of the isotopic composition of some mixtures prepared within the STELLAR project and sent to other project partners for analysis in the past two years. The results of the tests carried out are presented in this work, together with some future perspectives for the realization of primary reference mixtures of CO₂ in air at know isotopic composition on a larger scale.

How to cite: Rolle, F., Durbiano, F., Pavarelli, S., Pennecchi, F. R., and Sega, M.: Realisation of primary mixtures of CO2 in air at known isotopic composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13177, https://doi.org/10.5194/egusphere-egu24-13177, 2024.