451 research outputs found
Uranium, protactinium and thorium radionuclide activities in surface sediments of the continental slope of the Argentine basin
No full textThis is a set of bulk sediment analyses of 230Th, 232Th, 231Pa as well as uranium isotopes in surface sediments from the continental slope of the Argentine basin. Samples were subject to full digestion, and radioisotope data were determined using isotope dilution after ion chromatographic separation, electroplating and counting via alphaspectrometry (233Pa yield tracer: beta-counting) by Steffen Niemann as part of his diploma thesis in 2003 (supervision FU Berlin- Prof. Heubeck/ AWI Bremerhaven-Dr. Walter Geibert and Prof. Michael Schlüter)
Master track of POLARSTERN cruise PS144 in 1 sec resolution (zipped, 243 MB)
No full textRaw data acquired by position sensors on board RV Polarstern during expedition PS144 was processed to receive a validated master track which can be used as reference of further expedition data. During PS144 two Trimble Marine R750 GPS receivers and the iXBlue HYDRINS hydrographic survey inertial navigation system were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.awi.de) with a resolution of 1 sec. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track
Radiumisotope als Tracer für den Elementkreislauf an ozeanischen Randgebieten
No full textTrace elements (TEs) play crucial roles in regulating ocean processes including marine biogeochemical cycles, and are therefore vital to support marine life. Understanding the biogeochemical cycling of TEs requires knowledge of their sources/ sinks and transport in the oceans. Radium isotopes are suitable tools to study inputs of elements from the continental margins, as they are produced by the decay of thorium isotopes in sediments, and are soluble in seawater. Therefore, in this Ph.D. thesis, I used Ra isotopes to determine boundary TE fluxes from two diverse environments that constrain the major TE sources, including shelf sediments in an Arctic shelf region and in an eastern boundary system off the western African coast, as well as rivers such as the River Congo.
First, the distributions of the dissolved and total dissolvable TEs (Cd, Fe, Ni, Cu, Zn, Pb, Mn, and Co) were investigated in the Chukchi Sea and 228Ra isotope was applied as tracer of benthic TE inputs. The results show that elevated benthic TE inputs on the Chukchi shelf provided suitable conditions for phytoplankton blooms. The 228Ra activities in spring appear to be 2-fold higher than in summer, which was a surprising observation and requires further investigation.
Next, 228Ra was used to investigate the influence of the Congo River on surface ocean TE concentrations in the South Atlantic Ocean. The results show that the Congo River plume constitutes a large and unexpected input of TEs (Fe, Mn, and Co) into the South Atlantic.
Finally, Ra isotopes were used to investigate a number of key ocean boundary processes in the Southeast Atlantic Ocean. Upwelling in the Benguela region is visible in the Ra distributions, and elevated Ra isotopes, Fe (II) and Si concentrations were observed in the Benguela oxygen minimum zone, possibly due to inputs from the reducing shelf sediments, or submarine groundwater discharge along the Namibian shelf.Spurenelemente spielen eine zentrale Rolle in der Regulation ozeanischer Prozesse einschließlich des marinen biogeochemischen Kreislaufs und sind dadurch eine zentrale Voraussetzung für das Leben im Meer. Das Verständnis der biogeochemischen Kreisläufe der Spurenelemente basiert auf dem Wissen um deren Quellen, Senken und Transportwege innerhalb des Ozeans. Die Radiumisotope, welche als Zerfallsprodukt von Thorium in Sedimenten entstehen, sind wasserlöslich und haben sich als nützliche Werkzeuge herausgestellt, die den Input von solchen Elementen aus den kontinentalen Hängen nachvollziehen lassen. Diese verwende ich in der vorliegenden Dissertation, um die bedeutendsten Spurenelementquellen zu beleuchten, die den Austausch zwischen Schelfsedimenten und dem angrenzenden Ozean vornehmen. Dies geschieht anhand zweier kontrastierender Umgebungen, dem arktischen Schelf und des östlichen „Grenzsystems“ vor der Küste Westafrikas, das auch Flusseinträge wie zum Beispiel aus dem Kongo beinhaltet.
Zunächst wurde die Verteilung der gelösten und säurelöslichen Spurenelemente (Cd, Fe, Ni, Cu, Zn, Pb, Mn und Co) in der Tschuktschensee untersucht. Als Tracer zur Bestimmung benthischen Eintrags wurde dort 228Ra verwendet.
Des Weiteren wurde 228Ra verwendet, um den Einfluss des Kongo, auf die im oberen Ozean befindlichen Spurenelemente im Südatlantik zu untersuchen. Die Ergebnisse zeigen, dass die Flusswasserfahne des Kongo einen unerwartet großen Eintrag bioessentieller Spurenelemente in den Südatlantik ausmacht.
Mit Hilfe der Radiumisotope wurden abschließend eine Reihe von Schlüsselprozessen im Grenzflächenaustausch des Südost-Atlantiks untersucht. Der Auftrieb der Benguela-Region ist ebenfalls in der Radiumverteilung ersichtlich. Gleichzeitig weisen erhöhte Konzentrationen der Radiumisotope, Fe (II) und Si in der Benguela-Sauerstoffminimumzone auf Zufuhr aus reduzierenden Schelfsedimenten oder aus unterseeischem Grundwasseraustritt entlang des Namibianischen Schelfs hin
Master tracks in different resolutions of POLARSTERN cruise PS144, Tromsø - Bremerhaven, 2024-08-09 - 2024-10-13
No full textRaw data acquired by position sensors on board RV Polarstern during expedition PS144 was processed to receive a validated master track which can be used as reference of further expedition data. During PS144 two Trimble Marine R750 GPS receivers and the iXBlue HYDRINS hydrographic survey inertial navigation system were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.awi.de) with a resolution of 1 sec. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track
Actinium-227 als Tracer für Advektion und Mischung in der Tiefsee = Actinium-227 as a tracer for advection and mixing in the deep-sea
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Oxygen profiles, pore-water geochemistry and solid phase data of surface sediments retrieved from the eastern continental shelf of the Antarctic Peninsula
No full textDuring the PS118 research cruise with the German research vessel RV POLARSTERN (Feb 2019- April 2019), sediments were collected with a multicorer from 7 stations along a 400 mile transect from the eastern shelf of the Antarctic Peninsula to the West of the South Orkney Islands. A total of 69 high-resolution O2 profiles were measured in 23 cores in the upper sediment layer using optical microsensors (Optodes, Pyroscience) in order to determine oxygen penetration depths and diffusive oxygen uptake (DOU). Pore-water samples were taken at depth resolutions of 1 cm from 0-10 cm and below 10 cm with a resolution of 2 cm down to a maximum depth of 30 cm. Sediments of parallel cores were cut at the same depth resolution for solid-phase contents. Pore-water analyses of trace element such as dissolved iron (DFe) and manganese (DMn), dissolved inorganic carbon (DIC), hydrogen sulfide (H2S) and nutrients such as ammonium (NH4+), phosphate (PO4³), nitrate (NO3-), nitrite (NO2-) and silicate (SiO3²−) were measured. For solid-phase analyses, freeze-dried and ground sediment samples were measured for TOC and TN. At 5 stations, Al, Fe, Mn, P and S content was measured after total acid digestion. At the same 5 stations, excess 210Pb was measured in freeze-dried and homogenized sediments
Oxygen profiles of surface sediments retrieved from the eastern continental shelf of the Antarctic Peninsula during RV POLARSTERN cruise PS118
No full textDuring the PS118 research cruise with the German research vessel RV POLARSTERN (Feb 2019- April 2019), sediments were collected with a multicorer from 7 stations along a 400 mile transect from the eastern shelf of the Antarctic Peninsula to the West of the South Orkney Islands. A total of 69 high-resolution O2 profiles were measured in 23 cores in the upper sediment layer using optical microsensors (Optodes, Pyroscience) in order to determine oxygen penetration depths and diffusive oxygen uptake (DOU). Pore-water samples were taken at depth resolutions of 1 cm from 0-10 cm and below 10 cm with a resolution of 2 cm down to a maximum depth of 30 cm. Sediments of parallel cores were cut at the same depth resolution for solid-phase contents. Pore-water analyses of trace element such as dissolved iron (DFe) and manganese (DMn), dissolved inorganic carbon (DIC), hydrogen sulfide (H2S) and nutrients such as ammonium (NH4+), phosphate (PO4³), nitrate (NO3-), nitrite (NO2-) and silicate (SiO3²−) were measured. For solid-phase analyses, freeze-dried and ground sediment samples were measured for TOC and TN. At 5 stations, Al, Fe, Mn, P and S content was measured after total acid digestion. At the same 5 stations, excess 210Pb was measured in freeze-dried and homogenized sediments
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