REDOX - Geochemistry and redox proxie’s signature under the diverse environmental conditions: towards better understanding of the past redox

Kategorija

Projekti Hrvatske zaklade za znanost

Glavni istraživač

E

B

Elvira Bura Nakić, dr.sc.

Elvira.Bura.Nakic@irb.hr

099 347 3334

Project summary

Reconstructing the chemistry of past Earth’s atmosphere and ocean, and their redox states, has gained enormous attention recently. Ocean sediments provide geochemical records through much of Earth’s history.The reconstructing past environmental conditions from such archives, depends on the quality of data that can be extracted from these records. The reliability of identifying good indicators of specific environmental condition (i.e., proxies), and the processes controlling sequestration from the aqueous phase into the sediments, are key points in the “reconstruction chain”. The enrichment of several redox-sensitive trace elements, as well as their isotopic composition in (anoxic) sediments have previously shown to carry important information about the mechanism of their removal and the prevailing redox conditions within the water column at the time of sediment deposition. Yet, to fully capitalize potential of these emerging redox-sensitive proxies in reconstructing Earths’ past oxygenation state, a thorough understanding of these proxies geochemistry in modern environments is mandatory. This project is aimed at better understanding the geochemistry of selected redox proxies under a range of critical environmental redox conditions. We aim to further characterize the redox chemistry on proxies which already have some maturity, including significant work by the PI (Mo and U), and by targeting the newly emerging elements such are V and Re. Combining these proxies will provide an improved framework for interpreting the geochemistry of specific redox conditions and separate global ocean signatures from localized effects in the sediments. The research within project REDOX will target following subjects: i.) improve the usage of coupled Mo-U abundance and isotopic composition as redox proxy; ii.) development/implementation of specific analytical procedures for determining V redox speciation and Re pre-concentration; iii.) determine the processes controlling Re and V abundance and mobility in sediments and overlying waters spanning oxic, hypoxic and anoxic conditions. Within i.) we aim to investigate the influence of seasonal changes in sedimentary redox conditions on Mo-U isotopic composition of the sediments and porewaters. This investigation will significantly contribute to the understanding how to recognize/distinguish influence of localized diagenetic processes within sediments on the redox proxies global isotopic signatures within the past.REDOX within ii.) aims to develop particular chromatographic V redox speciation technique which together with the Re pre-concentration method is representing distinctive analytical approach in investigating redox sensitive metals geochemistry.The goal of REDOX within iii.) is to obtain detailed information on V and Re abundance as well and on V redox species within sediment, interstitial water and water column. The nature of interactions between V and organic matter will be studied also within iii.) what all together will contribute to the further development of V and Re as new redox indicators.The research within REDOX aims to combine particular analytical procedures (chromatographic redox V speciation, Re pre- concentration) together with the several others classical analytical techniques (chromatography, spectrophotometry, MC-ICP-MS and electrochemistry) as well and uniqueness of the study sites along the eastern Adriatic Coast (Croatia).The research performed within the framework of REDOX is expected to have high impact in the field of environmental geochemistry and isotope geochemistry, and will significantly contribute to our fundamental understanding of the redox-induced transformations of Mo, U, V and Re within modern and ancient environments.

News - REDOX

February 2019

Laboratory Martinska - ionic chromatograph

April 2019

PhD student Lucija Knežević spent 3 weeks on the Faculty of Biology, Chemistry and Earth sciences, University of Bayreuth. In the period from 01.04.2019. to 22.04. 2019. she worked in Enviromental Geochemistry Group on the development of vanadium speciation method in environmental samples using coupled IC-ICP-MS system.

June 2019

Laboratory at Ruđer Bošković Institute Zagreb - IC connected with the ICP-MS

August 2019

Bachelor student Niclas Einert from Faculty of Biology, Chemistry and Earth sciences, University of Bayreuth spent 2 months within the DAAD RISE WW grant at the Laboratory Martinska working on vanadium determination and sequential extraction within the estuarine and anoxic sediments.

Sampling August-September 2019