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

Non-traditional isotopes as identifiers of authigenic carbonates, 1.7.2018 - 30.06.2021, Sonja Lojen

About


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.

News

Participation at 3rd MASSTWIN Exploratory Workshop in Halle

20.11.2018

Two posters presented at the Workshop on the use of stable isotopes techniques for assessing biogeochemical cycling of contaminants and nutrients

Objectives

→ 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.