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Unraveling Pathways of Biovolatilization of Selenium from Seawater: New Insights from Organic speciation and Transformations

Applicant Winkel Lenny
Number 179104
Funding scheme Project funding (Div. I-III)
Research institution Institut für Biogeochemie und Schadstoffdynamik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Environmental Sciences
Start/End 01.11.2018 - 31.10.2022
Approved amount 770'000.00
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Keywords (5)

selenium; fluxes; seawater; speciation; volatilization

Lay Summary (German)

Lead
Selen (Se) ist ein essenzielles Spurenelement für die Menschheit. Da Se in der Atmosphäre vor kommt, fungieren atmosphärische Depositionen wie der Niederschlag als Mikronährstoff für Kulturböden und die Vegetation. Untersuchungen zeigen auf, dass das Leben im Ozean eine wichtige Quelle für das Selenvorkommnis in der Atmosphäre darstellt. Ozeanische Mikroorganismen wie beispielsweise Algen können Selen aus dem Meerwasser aufnehmen und es in eine flüchtige Form umwandeln, welche anschliessend in die Atmosphäre entweicht. Es ist noch immer grösstenteils unbekannt was der grundlegende Mechanismus für die Produktion von volatilen Se-Phasen ist, welche Organismen daran beteiligt sind und wie viel volatiles Se produziert wird.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Unser übergeordnetes Ziel ist es, zu untersuchen wie flüchtiges Se produziert wird in der Meeresumwelt, was mit dieser chemischen Form von Se passiert, bspw. wie viel volatiles Se wird produziert, und wie viele volatiles Se wird in eine nicht-flüchtige Form umgewandelt. Für die Erfassung und Messung von flüchtigem Se werden wir während den Forschungsfahrten auf dem Schiff im mediterranen und baltischen Meer neue Methoden entwickeln und anwenden. Wir werden flüchtiges Se im Meerwasser, Luft- und Meeres-Mikroorganismen analysieren sowie untersuchen wie die verschiedenen Umweltfaktoren die chemischen Verbindungen und Konzentrationen von Se in diesen Kompartimenten beeinflussen. 

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Unsere Studie wird wichtige und neue Erkenntnisse liefern, welche das Verständnis vom biochemischen Kreislauf von Se im Meer sowie den Transport von Se vom Meer in die Atmosphäre verbessern wird. Die gemessenen atmosphärischen Flüsse sind ein wichtiger Input für biogeochemische Modelle um Nährstoffflüsse und die Se-Verteilung in der Umwelt vorherzusagen. 

Direct link to Lay Summary Last update: 01.11.2018

Responsible applicant and co-applicants

Employees

Abstract

Selenium (Se) is an essential trace element for humans. The atmosphere is known to be an important reservoir of Se, which can supply Se to terrestrial environments and food chains via atmospheric deposition. Atmospheric budget estimates show that the marine biosphere accounts for the largest part of natural emissions to the atmosphere and thus constitutes an important atmospheric Se source. However, the production mechanisms and fluxes of volatile selenium from marine environments remain central uncertainties in the global Se cycle. There is currently very little quantitative and qualitative information available about the role of marine microorganisms (algae, i.e., phytoplankton and bacteria) in producing (and consuming) volatile organic Se species, and how these processes are affected by environmental conditions. Furthermore, biotransformation pathways of Se in seawater are largely unknown due to a lack of organic speciation measurements of Se in natural seawaters and phytoplankton/ bacteria assemblages. This project will tackle these research gaps in three work packages (WP). WP 1 (PhD student 1) will investigate speciation and biotransformation of Se in synthetic and natural seawaters as a function of different environmental factors. It involves i) the development and application of methods for quantifying Se speciation in the dissolved phase by High Pressure Liquid Chromatography hyphenated to Inductively Coupled Plasma - tandem Mass Spectrometry (HPLC-ICP-MS/MS), ii) laboratory experiments studying biotransformations of Se by marine algae and bacteria and iii) analyses of total Se and speciation of natural seawater samples that will be collected during planned research cruises in the Mediterranean Sea and the Baltic Sea. WP 2 (PhD student 2) is aimed at investigating atmospheric fluxes of volatile organic Se species and mechanisms of Se biomethylation. A main task in WP2 is setting up, testing and optimizing an automated and high-throughput method for gas trapping and analytical methods for determination of volatile Se and S species, using Thermo-Desorption - Gas Chromatography - ICP-MS/MS (TD-GC-ICP-MS/MS). Gas trapping will be carried out during the research cruises to determine concentrations and fluxes of volatile Se and S species. Onboard incubation studies will be conducted as well, revealing the first mechanistic insights into biomethylation pathways in natural seawaters. WP3 (Postdoc) is aimed at obtaining a better understanding of Se cycling and dynamics in the surface seawater by determining temporal and spatial variability in Se partitioning between dissolved and colloidal/particulate phases, analyzing intracellular Se content and speciation and determining bioconcentrations factors in different plankton size fractions. These studies will use samples from the cruises as well as (bi)monthly samples of different plankton size fractions from the Baltic Sea, which will be collected over 2.5 years, to study Se bioconcentration over longer time scales. Furthermore, the Postdoc will collect and curate all data obtained in the project and analyze relationships between obtained data using advanced statistical methods. At the end of the project, a database containing all field and experimental data will be made available to the public. Expected results are i) further insight into the role of phytoplankton and/ or bacteria in volatile Se emissions from seawaters, ii) information on partitioning of Se between dissolved and particulate phases and (organic) Se speciation in seawaters and different plankton fractions as a function of environmental variables and iii) first insights into the mechanisms of biomethylation in natural seawaters. The project will present an important advancement of our understanding of biomethylation specifically and Se cycling in surface seawaters, in general. Furthermore, the data produced in this project will be crucial for the development of biogeochemical models that predict the transfer of selenium between different environmental compartments, i.e., biosphere, hydrosphere, and atmosphere.
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