EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The importance of appropriate isotope reference standards for determination of the isotopic composition of C and O in atmospheric CO2

Bor Krajnc1, Samo Tamše1, and Nives Ogrinc1,2
Bor Krajnc et al.
  • 1Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
  • 2Jožef Stefan International Postgraduate School, Ljubljana, Slovenia

      Our process-based understanding of stable isotope signals, as well as technological developments, has progressed significantly, opening new frontiers in marine interdisciplinary research. This has promoted the broad utilisation of carbon and oxygen isotope applications to gain insight into carbon cycling in marine ecosystems and their interaction with the atmosphere.

Our study was performed in the Gulf of Trieste in the N Adriatic where the influence of biological processes, riverine loads and local climate conditions on the atmosphere-water CO2 exchange and on the carbonate system equilibrium was investigated, in order to elucidate what drives the CO2 exchange and to estimate the vulnerability of the Gulf of Trieste to acidification processes. On an annual scale, the Gulf of Trieste clearly acts as a sink of CO2, strongly controlled by the seasonal variability of water temperature, biological processes, wind speed and riverine inputs. The calculated air-sea CO2 flux was estimated to be -1.47 ± 1.41 mol C m-2 yr-1. The sink was generally stronger during the winter months, whereas during early summer and autumn the CO2 fluxes were lower. It was interesting to note that the atmospheric CO2 concentrations exhibited large fluctuations on a daily basis, as well as on a seasonal time scale. The average atmospheric CO2 concentration during our study in 2013 was 438 ± 16 ppm. This is significantly higher than the global average, which, at the time was around 400 ppm. Further The isotopic composition of carbon in atmospheric carbon dioxide (δ13CCO2,air) values panned from -12.7‰ to -9.1‰ with an average value of -10.8 ± 0.9‰. This is considerably different to the “background” value of -8‰ (from NOAA/ESRL) and can most probably be attributed to the presence of fossil fuel emissions. The results are comparable with the data obtained in the Adriatic between Ravenna and Otranto.

The presented study indicate that the quality and comparability of datasets is critical to improve the estimation of processes that influence the carbon dynamics in marine environment. Thus, the implementation of the principle in our laboratory, the monitoring of our measurement quality, validation and status of newly developed gas CO2 reference materials (SIRS1, SIRS2 and SIRS3) as a part of SIRS project will be also presented.

How to cite: Krajnc, B., Tamše, S., and Ogrinc, N.: The importance of appropriate isotope reference standards for determination of the isotopic composition of C and O in atmospheric CO2, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18746,, 2020

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