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Faculty for Biology, Chemistry, and Earth Sciences

Environmental Geochemistry Group - Prof. Dr. Britta Planer-Friedrich

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Bachelor Thesis

Understanding vanadium geochemistry in estuaries and lakes in Croatia

Niclas Einert (10/2018-12/2019)

Support: Britta Planer-Friedrich, José Miguel León Ninin

Due to its variable redox chemistry, Vanadium (V) belongs to the group of Redox Sensitive Elements (RSEs) and is an emerging paleo–redox–proxy, used to reconstruct ancient atmospheric and oceanic chemistry with special focus on the Great Oxidation Event (GOE) and the change in anoxic to oxic conditions. In contrast to the known redox–proxies like Uranium and Molybdenum, not much is known about geochemistry of Vanadium yet. To get a better understanding of Vanadium and its behavior in oxic and anoxic environments a project carried out by the Ruđer Bošković-Institute was started, to analyze an anoxic sampling site (Lake Rogoznica, Dalmatian region of Croatia), mirroring ancient oceanic conditions. This thesis contributes to the work of the project by quantifying and comparing the overall amounts of V in sediment samples from Lake Rogoznica (anoxic) and River Krka (oxic), as well as looking for possible influences on the Vanadium concentrations of the sediments by analyzing the background rocks, the water phase and the particle phase. Furthermore Fe and Al were measured to look for possible correlations with the V concentration. To achieve these goals, total digestions were performed, as well as sequential extractions to obtain information about the V binding forms. All samples were measured via ICP-MS. Results showed that contrary to the expectations V concentrations were significantly lower in the analyzed anoxic sediments than in the oxic sediments, mostly related to the V concentrations of the source rocks. Analyses showed a strong correlation to the Al-silicates and an increase of V with depth in the oxic sediments. The anoxic sediments were mainly influenced by the high sedimentation rates in Lake Rogoznica and the high contents of organic matter. Biggest influences on the sediment concentrations of V are the composition regarding the geological background, the redox conditions and the amount of organic material contributing to the sedimentation. This study showed the complexity of V geochemistry and that there is still a lot to understand from V geochemistry, especially in estuarine and anoxic systems.

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