J1-9179 - Non-traditional isotopes as identifiers of authigenic carbonates

Non-traditional isotopes as identifiers of authigenic carbonates, 1. 7. 2018 - 30. 6. 2021, Sonja Lojen


Authigenic carbonate has been invoked as the third major global sink of CO2, and quantitative estimates of its production have so far been made only for marine carbonates. The first estimates in terrestrial environment were made based on Sr isotopes (δ88/86Sr) in river water and the results indicate that this sink is most probably largely underestimated. Consequently, the magnitude of terrestrial carbon fluxes and terrestrial carbon mass balance should to be reconsidered.

This project aims to validate advanced isotopic tools for identification and quantification of authigenic carbonate in terrestrial sediments and aquifers in areas dominated by carbonate lithology. As identifiers of authigenic carbonate, ratios of so-called non-traditional isotopes of Mg, Sr, U and Mo will be explored (the term “non-traditional isotopes” applies to those which are analysed using advanced plasma source mass spectrometry with multiple collectors – MC-ICP-MS). The goal of the project is to develop an analytical toolkit for differentiation of authigenic carbonate phases from detrital carbonate in complex sedimentary settings in areas dominated by carbonaceous lithology.


NT-ISO at IASWS 2022


On 13-15 June, the 15th International Symposiun on the interactions between sediments and water was held in Piran in hybrid form. We presented a study on the use of U and Sr isotope ratios in river carbonate as quantitative identifiers of authigenic carbonate.

Last sampling completed


The last sampling campaign in »Krka« National park, Croatia, was conducted in the first week of April in the framework of the bilateral collaboration project »Non-traditional isotopes as a new tool for estimation of continental CO2 sinks«. 

Leja Rovan defended a PhD Thesis


On November 3, 2021, Leja Rovan defended her PhD thesis entitled “Method for the determination of uranium isotope ratios and its application as a novel geochemical tracer” at the Jožef Stefan International Postgraduate School.

Sampling campaign in NP Krka completed


In the first week of September, lacustrine tufaceous samples were taken from river Krka at Brljan Lakes in “Krka” National Park, Croatia, for the analyses of isotopic composition of Mo, U, Sr and Mg in the sediment and interstitial water.


→ To apply advanced analytical tools - non-traditional isotopes and 2D MS mapping with laser ablation ICP-MS combined with field emission scanning electron microscopy with energy dispersive microanalysis - for the analysis of the formation of authigenic carbonate phases in freshwater sediments and aquifers;

→ To extend the knowledge on non-traditional isotopes of U, Th, Mo, Sr and Mg in marine environments to freshwater environments, so as to identify and quantify authigenic carbonate precipitation in terrestrial aquatic environments and in karstic aquifer;

→ To identify and quantify the extent of authigenic carbonate precipitation in recent sediments with a combination of traditional geochemical tools (i.e. elemental ratios, stable isotopes of C and O, C-14) for determination of the origin of C in carbonates and with new isotopic tools to identify and quantify the extent of authigenic carbonate precipitation in recent sediments.

The test environments are the (1) karstic limestone and dolostone aquifer recharging the river Ljubljanica, (ii) tufa barriers in Krka river and (iii) lacustrine carbonaceous sediments formed in lentic sections of Krka river. The field studies will be supported with laboratory mesocosm experiments, conducted to obtain information on element partition and isotope fractionation between water and carbonate, which cannot be measured directly in discrete samples obtained in complex natural environments.

Project phases

COVID-19 lockdown and the project

Because of COVID-19 crisis, the laboratory work and the fieldwork in Krka National Park were hindered. The work on mesocosm experiments was thus delayed, and the sampling of lacustrine sediments in Krka National Park is postponed to September 2021. The field study of isotope fractionation of redox-sensitive U and Mo in organic-rich sediment columns with redox boundary are therefore expected in 2022.


Phase 1: Development and adaptation of advanced (micro)analytical techniques

Phase 2: Mesocosm experiments

Phase 3: Case studies

Phase 4: Synthesis and dissemination

Project results

Scientific papers:

Rovan, L., Štrok. M. 2019. Optimization of the sample preparation and measurement protocol for the analysis of uranium isotopes by MC-ICP-MS without spike addition. Journal of Analytical Atomic Spectrometry 34 (9), 1882-1891, DOI: 10.1039/C9JA00144A

Rovan, L., Lojen, S, Zuliani, T., Kanduč, T., Petrič, M., Horvat, B., Rusjan, S., Štrok, M. 2020. Comparison of Uranium Isotopes and Classical Geochemical Tracers in Karst Aquifer of Ljubljanica River Catchment (Slovenia). Water 12, 2064; doi:10.3390/w12072064

Rovan, L., Zuliani, T., Horvat, B, Kanduš, T., Vreča, P., Jamil, Q., Čermelj, B., Bura Nakić, E., Cukrov, N., Štrok, M., Lojen, S. 2021. Uranium isotopes as a possible tracer of terrestrial authigenic carbonate, Science of the Total Environment 797, 14903,  https://doi.org/10.1016/j.scitotenv.2021.149103

Master Thesis

Jamil, Q. 2021. The evaluation of stable isotopes of carbon and strontium as tracers for estimation of CO2 storage in recent tufa in river Krka (Croatia). Master thesis, Jožef Stefan International Postgraduate School, 63 pp.

PhD Thesis

Rovan, L. 2021.  Method for the determination of uranium isotope ratios and its application as a novel geochemical tracer. Doctoral dissertation, Jožef Stefan International Postgraduate School, 143 pp.



Research presented at national and international conferences:

10th Jožef Stefan International Postgraduate School Students' Conference and 12th Young Researchers' Day 10th and 11th May 2018, Piran, Slovenia

16th Radiochemical Conference, 13-18 April 2018, Mariánské Lázně, Czech Republic

9th Mid-European Clay Conference - 09 MECC, Zagreb, Croatia. 17-21 September 2018

Uranium-biogeo: International Conference Uranium Biogeochemistry, October 21-26 2018, Monte Verità, Ascona, Switzerland

Workshop on the use of stable isotopes techniques for assessing biogeochemical cycling of contaminants and nutrients, 14 – 16 November 2018, Helmholtz Centre for Environmental Research, Halle, Germany

11th Jožef Stefan International Postgraduate School Students' Conference and 13th Young Researchers' Day, 15thand 16th May 2019, Planica, Slovenia

Goldschmidt 2019, 18 – 23 August 2019, Barcelona, Spain

24thInternational Symposium on Environmental Biogeochemistry, September 22-27, 2019, Potsdam. Potsdam: Helmholtz Centre, 2019

EGU General Assembly 2021, April 19-30, 2021, virtual conference (Vienna, Austria)

Goldschmidt Virtual 2021, July 4-9, 2021 (Lyon, France) 

Talk EGU 2021 Lojen et al.: abstract 

Talk EGU Rovan et al.: abstract

Talk Goldschmidt 2021 Gorenčič et al.: abstract,  presentation 

Talk Goldschmidt 2021 Lojen et al.: abstractpresentation 

Talk Goldsmidt 2021 Rovan et al.: abstractpresentation

https://www.iasws2022.si/, June 13-15, 2022 (Piran, Slovenia)

Talk ISEB2022 Lojen et al.: abstract, presentation (pdf)