Research Interests
My research focuses on understanding environmental fate of emerging technologically critical trace elements and toxic metal(oid)s, and on deciphering their chemical transformation in aquatic systems. Importantly, my scientific approach focuses on redox speciation, instead of total concentrations, as the key parameter controlling geochemical behaviour and environmental impact of these elements. Central part of my scientific approach is development and application of advanced analytical methodologies for accurate determination of trace environmental concentrations and chemical forms of trace metal(oid)s in vulnerable aquatic environments such as freshwater and estuaries. In addition, I also investigate interactions between trace elements and natural organic ligands to understand complex stabilisation and transport mechanisms of emerging pollutants. Overall, my scientific goal is to contribute to better understanding of transport and transformation of emerging trace metal contaminants in aquatic ecosystems to support its protection in the future.
Current project
2025 – 2027 Deciphering the geochemical cycle of Tellurium (Te): Comparative study of its transport and redox transformations in pristine and industrially impacted estuaries TeTRANS, Alexander von Humboldt research fellowship
As the global economy shift its focus towards sustainable energy sources, the demand for tellurium (Te), a technologically critical element, is rapidly growing. Despite its importance, the environmental implication of extensive Te usage to meet current technological needs are still poorly understood. With this project in the Koschinsky group, I aim to address key knowledge gaps in the geochemical cycling of tellurium (Te), by investigating its redox transformations, transport mechanisms, and interactions with dissolved organic matter (DOM) across various environmental compartments, from estuaries to open-ocean waters. The study will explore pristine DOM-rich estuaries (such as the Amazon and Parà Rivers), alongside industrially impacted systems (such as the Elbe, Weser, and Ems estuaries), to compare Te behaviour under natural and anthropogenic influences.
The primary objectives are to: I) Adapt and implement analytical techniques for Te redox speciation in estuarine samples, II) Investigate Te redox transformations and mobility in estuarine systems with varying geochemical drivers through all environmental compartments, III) define through which mechanisms DOM controls Te mobility and transport in the estuarine systems, IV) Identify physico-chemical factors which cause Te and Se fractionation in aquatic environments, and V) Validate existing thermodynamic databases for Te redox speciation modeling in natural waters.
By systematically addressing natural and anthropogenic drivers of Te cycling in dynamic estuarine systems, this research will elucidate Te mobility, redox transformations and its transport mechanisms to the open ocean waters. Additionally, it will improve our understanding of alternative ways to studying Te, including comparison with Se geochemistry and modeling. Overall, project will help clarify geochemical cycle of Te, and support its risk assessment for the preservation of aquatic environments for the future.
Former projects
2023-2025 Study of the mobility of selenium in a natural environment in the context of redox gradient in mining drainages in the Salsigne district (CNRS), PostDoc, Montpellier, France.
2019-2023 Geochemistry and redox proxie’s signature under the diverse environmental conditions: towards better understanding of the past redox (HRZZ), PhD student, Šibenik, Croatia.
List of publications
- Knežević, L., Cukrov, N., Bura-Nakić, E. (2024): Vanadium redox speciation in the acid-extractable phase of Krka River estuary surface sediment. Marine Chemistry, (267), 104452.
- Živković, I., Bura-Nakić, E., Knežević, L., Helz, G. (2023): Deposition of Mo, Re and U under contrasting redox conditions; assessment of the [Re/Mo]SW redox proxy. Geochimica et Cosmochimica acta, (359), 176-190.
- Knežević, L., Zanda, E., Bura-Nakić, E., Filella, M., Sladkov, V.* (2023): Vanadium(IV) and vanadium(V) complexation by succinic acid studied by affinity capillary electrophoresis. Simultaneous injection of two analytes for equilibrium studies. Journal of Chromatography A, (242), 463941.
- Knežević, L., Bura-Nakić, E.* (2023): Investigation of thiol compounds (L-cysteine, thioacetic acid, and ethanethiol) with V(V) and V(IV) using combined spectroscopy and chromatography. Journal of Inorganic Biochemistry, (242), 112158, 9.
- Bura-Nakić, E., Knežević, L., Mandić, J. (2022): Chromatographic and spectrophotometric studies of vanadate (V) reduction by 3-mercaptopropionic acid. Journal of Inorganic Biochemistry, (230), 111747, 8.
- Bura-Nakić, E., Knežević, L., Mandić, J., Cindrić, J., Omanović, D. (2021): Rhenium distribution and behavior in the salinity gradient of a highly stratified estuary and pristine riverine waters (The Krka River, Croatia). Archives of environmental contamination and toxicology, 81, 564-573.
- Knežević, L., Omanović, D., Bačić, N., Mandić, J., Bura- Nakić, E.* (2021): Redox speciation of vanadium in estuarine waters using improved methodology based on anion exchange chromatography coupled to HR ICP-MS. Molecules, (26) 9, 2436, 15.
- Knežević, L., Cukrov, N., Bura-Nakić, E.* (2020): Ion-exchange chromatography as a tool for investigating vanadium speciation in sediments: preliminary studies. Journal of Soil and Sediment, 20, 2733-2740.