Project phases

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

The focus of this WP will be on the optimization of sample preparation procedures and measurements of the isotopic ratios of Mg, Se, Mo, Th and U using MC-ICP-MS. To achieve accurate and precise measurements, the blanks have to be reduced to the minimum and elements of interest have to be isolated from the matrix without any isotopic fractionation. For analysis of authigenic and allogenic carbonate phases, the dissolution of non-carbonate components will have to be avoided, and interferences with matrix elements will have to be eliminated. For the mapping of Mg, Sr, Mo and U in sediment and rock samples by laser ablation ICP-MS, sample preparation techniques for powdered samples will be optimized. Measurement protocols will be also optimized in terms of laser spot size and energy, as well as ICP-MS parameters such as introduction of collision gases and utilization of the full potential of triple quad ICP-MS for removal of spectral interferences.

Current status: Completed

- development and optimisation of methods for U isotope analyses is completed, the first scientific paper published in Journal of Analytical Atomic Spectrometry (read more)

- methods for extraction of Mg, Mo, Sr and U from environmental matrices optimised

- isotopic analyses of δ238U, 87/86Sr and δ88 Sr completed, analyses of δ26Mg in progress

- analytical procedures for determination of δ98Mo are optimised


Phase 2: Mesocosm experiments

The partition of U, Mo, Sr, and Mg and their isotope fractionation in simplified systems in controlled laboratory conditions will be determined with mesocorm experiments. Columns recirculation systems will be set up with samples of different types of sediment (bedrock, soil) using natural solutions with defined chemical composition. The main objectives of this work package are the (I) determination of element partition and isotope fractionation during dissolution of bedrock (aquifer); (II) determination of element partition and isotope fractionation during carbonate precipitation in karst-analogue conditions, and (III) estimation of authigenic carbonate end-member in oxic and anoxic conditions.

Current status: completed, programme changed because of COVID restrictions

 - leaching of carbonate-bound U from environmental matrices (soil, bedrock, tufa) was successfully elaborated and isotope fractionation of U during carbonate precipitation were successfully elaborated in the field study in Krka National park, which confirmed the mechanisms of isotope fractionation of U during co-precipitation of U with carbonate

 - leaching experiments of Mg and Sr from bedrock and soil are completed and the results are elaborated in the MSc thesis by M. Gorenčič

 - Mo isotope fractionation in leached carbonate fraction in lacustrine sediment are studied in the MSc. thesis by Žan Hauptman


Phase 3: Case studies

The performance of U, Th, Mo, Sr and Mg isotopes as identifiers of authigenic carbonate will be analysed in three types of natural environments: (I) karstic limestone/dolostone aquifer of the river Ljubljanica; (II) predominantly authigenic carbonate (tufa) sediment formed in oxic conditions in river Krka and (III) lacustrine carbonate formed in anoxic sediment.

Current status: On-going

- the study of U isotope fractionation in Ljubljanica aquifer is completed, results are presented in the paper “ Comparison of Uranium Isotopes and Classical Geochemical Tracers in Karst Aquifer of Ljubljanica River Catchment (Slovenia)” by Leja Rovan et al., Water 2020, 12, 2064; doi:10.3390/w12072064 

- the study on U isotopes as identifiers of authigenic carbonate in the catchment of tufa precipitating rivers Krka and Zrmanja, Croatia, is completed and published in Science of the Total Environment  “Uranium isotopes as a possible tracer of terrestrial authigenic carbonate” by Leja Rovan et al.

- the study of Sr and Mg fractionation in Krka and Zrmanja Rivers, Croatia, is completed and a publication is in preparation.

- the study of Sr isotope fractionation in Ljubljanica aquifer and in Krka River (Croatia) is complited and is presented in the MSc. Thesis by M. Gorenčič.

- lacustrine sediments in lentic sections (Brljanska jezera) were sampled in September 2021 and the analyses of elemental composition and traditional (O, C) isotopes in lake water, sediment and interstitial water are completed; isotope analyses of samples for Sr and Mg isotope ratios are in progress.

-  Mo isotope study of sediment and river water is in progress in the framework of a MSc thesis.


Phase 4: Synthesis and dissemination

The performance of analysed isotopic and geochemical identifiers will be assessed in terms of uncertainties determined in mesocosm experiments and in the field. The estimates of authigenic carbonate by non-traditional isotope identifiers will be compared to estimates obtained based on 13C and 14C analyses of bulk carbonates and dissolved inorganic C in each environment. As synthesis of the project, the estimate of the extent of C fixation in analysed environments and evaluation of the suitability of analysed identifiers will be made using common conceptual and hydrogeochemical models. The project results will be presented at scientific workshops and conferences and published as peer-reviewed articles in international scientific journals. Transfer of knowledge will proceed in terms of lectures, short courses and internships for students, as well as training of early stage researchers (BSc, MSc and PhD level).