| 1. |
- Friedrich, Jana, et al.
(författare)
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Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11, s. 1215-1259
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX (“In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies”, www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of watercolumn oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.
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| 2. |
- Wilson, Samuel T., et al.
(författare)
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Ideas and perspectives : A strategic assessment of methane and nitrous oxide measurements in the marine environment
- 2020
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 17:22, s. 5809-5828
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Tidskriftsartikel (refereegranskat)abstract
- In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption, and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climate-active trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.
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| 3. |
- Behrens, A, et al.
(författare)
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Oxomolybdenum(III, IV and V) complexes of thiofunctional ligands
- 2005
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 358:6, s. 1970-1974
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of [MoO2(acac)(2)] with Li2NS2S'(2), (S is a thioether, S' a thiophenolate function) yielded the compound Li-7(thf)(17){MoO}(8)center dot 10thf center dot hexane, where {MoO}(8) represents one [(MoO)-O-IV(NS2S'(2))] 1, three [(MoO)-O-III(NS2S'(2))](-) (2, linked, via the oxo group, to [Li(thf)3](+)) and two [(MoO)-O-V(S'(2))(2)](2-)(2) .A mixed-valent variant of 3, [{(MoO)-O-IV(S'(2))} {(MoO)-O-V(S'(2))}](-) (3b, with an additional [Li(thf)3](+) attached to S'), was also identified. The compounds model features pertinent to oxo-transferases containing the molybdopterin cofactor.
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| 4. |
- Gutiérrez Loza, Lucia, et al.
(författare)
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Air–sea CO2 exchange in the Baltic Sea—A sensitivity analysis of the gas transfer velocity
- 2021
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Ingår i: Journal of Marine Systems. - : Elsevier. - 0924-7963 .- 1879-1573. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- Air–sea gas fluxes are commonly estimated using wind-based parametrizations of the gas transfer velocity. However, neglecting gas exchange forcing mechanisms – other than wind speed – may lead to large uncertainties in the flux estimates and the carbon budgets, in particular, in heterogeneous environments such as marginal seas and coastal areas. In this study we investigated the impact of including relevant processes to the air–sea CO2 flux parametrization for the Baltic Sea. We used six parametrizations of the gas transfer velocity to evaluate the effect of precipitation, water-side convection, and surfactants on the net CO2 flux at regional and sub-regional scale. The differences both in the mean CO2 fluxes and the integrated net fluxes were small between the different cases. However, the implications on the seasonal variability were shown to be significant. The inter-annual and spatial variability were also found to be associated with the forcing mechanisms evaluated in the study. In addition to wind, water-side convection was the most relevant parameter controlling the air–sea gas exchange at seasonal and inter-annual scales. The effect of precipitation and surfactants seemed negligible in terms of the inter-annual variability. The effect of water-side convection and surfactants resulted in a reduction of the downward fluxes, while precipitation was the only parameter that resulted in an enhancement of the net uptake in the Baltic Sea.
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| 5. |
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| 6. |
- Steinhoff, Tobias, et al.
(författare)
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Constraining the Oceanic Uptake and Fluxes of Greenhouse Gases by Building an Ocean Network of Certified Stations : The Ocean Component of the Integrated Carbon Observation System, ICOS-Oceans
- 2019
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Ingår i: Frontiers in Marine Science. - : FRONTIERS MEDIA SA. - 2296-7745. ; 6
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Forskningsöversikt (refereegranskat)abstract
- The European Research Infrastructure Consortium "Integrated Carbon Observation System" (ICOS) aims at delivering high quality greenhouse gas (GHG) observations and derived data products (e.g., regional GHG-flux maps) for constraining the GHG balance on a European level, on a sustained long-term basis. The marine domain (ICOS-Oceans) currently consists of 11 Ship of Opportunity lines (SOOP - Ship of Opportunity Program) and 10 Fixed Ocean Stations (FOSs) spread across European waters, including the North Atlantic and Arctic Oceans and the Barents, North, Baltic, and Mediterranean Seas. The stations operate in a harmonized and standardized way based on community-proven protocols and methods for ocean GHG observations, improving operational conformity as well as quality control and assurance of the data. This enables the network to focus on long term research into the marine carbon cycle and the anthropogenic carbon sink, while preparing the network to include other GHG fluxes. ICOS data are processed on a near real-time basis and will be published on the ICOS Carbon Portal (CP), allowing monthly estimates of CO2 air-sea exchange to be quantified for European waters. ICOS establishes transparent operational data management routines following the FAIR (Findable, Accessible, Interoperable, and Reusable) guiding principles allowing amongst others reproducibility, interoperability, and traceability. The ICOS-Oceans network is actively integrating with the atmospheric (e.g., improved atmospheric measurements onboard SOOP lines) and ecosystem (e.g., oceanic direct gas flux measurements) domains of ICOS, and utilizes techniques developed by the ICOS Central Facilities and the CP. There is a strong interaction with the international ocean carbon cycle community to enhance interoperability and harmonize data flow. The future vision of ICOS-Oceans includes ship-based ocean survey sections to obtain a three-dimensional understanding of marine carbon cycle processes and optimize the existing network design.
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| 7. |
- Thapper, A, et al.
(författare)
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Synthesis and characterization of molybdenum oxo complexes of two tripodal ligands: reactivity studies of a functional model for molybdenum oxotransferases
- 2005
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; :21, s. 3566-3571
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N, N-bis(2-pyridylmethyl) amine (L - OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L - O)] PF6. Similarly, the reaction of N-(2-mercaptobenzyl)- N,N-bis(2-pyridylmethyl) amine (L -SH) with MoO2(acac)(2) leads to the formation of [MoO2(L - S)](+). The dioxo-molybdenum complex [MoO2(L - O)](+) reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV) O(L - O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L - O)] PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [( L - O) OMo(mu-O) MoO(L - O)](PF6)(2). The crystal structures of [MoO2(L - O)] PF6 and the mu-oxo bridged dimer are presented.
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