1,721,770 research outputs found
Pore water and solid phase data from deep-sea trench sediments
No full textSamples were collected during three expeditions with RV SONNE between 2014 and 2018 (cruises SO219, SO251 and SO261). Sediment cores were taken by using multicorer and gravity corer.
Alkalinity has been analyzed by gran titration of known quantities of pore water sample by addition of HCl on a micro stirring device. The accuracy of this method was better than 0.2 mM (data not shown). Dissolved iron (Fe2+) concentrations were analyzed photometrically at wavelength of 565 nm with a Hach Lange DR 2800 Photometer. Dissolved ammonium (NH4+) was detected using the PTFE tape gas separator technique. Dissolved Manganese concentrations were analyzed in acidified samples with an inductively coupled plasma optical emission spectrometer (ICP-OES; Varian Vista PRO). The precision was better than 3 % with a detection limit of 0.04 µM. Sulfate (SO42-) concentrations were determined by ion chromatography (Metrohm 861 Advanced Compact IC, Metrohm A Supp 5 column, 0.8 mL min‑1, conductivity detection after chemical suppression) in samples diluted 1:40 with Milli-Q-grade H2O. Dissolved methane (CH4) concentrations were analysed following the headspace method. For samples from the Japan Trench we used an Agilent Technologies 6890N gas chromatograph equipped with a flame ionization detector, while samples from Atacama Trench site GeoB22908 a ThermoFinnigan Trace gas chromatograph equipped with a flame ionization detector and a Carboxen-1006 PLOT fused-silica capillary column (0.32 mm by 30 m; Supelco, Inc., USA) was used. The stable carbon isotopic composition of methane in four samples from the Atacama trench was determined by duplicate analysis using a Trace GC Ultra coupled to a Delta Plus XP isotope ratio mass spectrometer via a GC Combustion III interface (all ThermoFinnigan). Information on the calculation of flux rates are given in the supplements.
Solid phase iron and manganese concentrations is sediments of core GeoB22908-2 were measured using the high-resolution (1 cm) semi-quantitative XRF (X-ray fluorescence) Avaatech at MARUM, performed with an excitation potential of 10 kV, a current of 250 mA and 30 s counting time. Scans were calibrated with quantitative XRF measurements on discrete samples using a PANalytical Epsilon3-XL XRF spectrometer equipped with a rhodium tube, several filters and an SSD5 detector and certified standard materials (e.g., GBW07309, GBW07316 and MAG-1). Scans of the bulk (Gamma Ray) density were conducted with a Multi-Sensor Core Logger (MSCL; GEOTEK®) at MARUM. The MSCL was equipped with a line scan camera for high-resolution core image acquisition.
Accelerator Mass Spectrometry measurements (AMS) of radiocarbon (14C) ages on TOC of samples from core GeoB22908-1 were carried out in the MICADAS radiocarbon laboratory at Alfred-Wegener Institute (AWI), Germany. 14C bulk ages are uncalibrated.
A programmed pyrolysis method (Hawk instrument, Wildcat Technologies, USA) at the Lithospheric Organic Carbon Lab (LOC) of the Department of Geoscience, Aarhus University, was used to measure TOC and the reactive organic carbon content in freeze-dried sediment samples. The Rock-Eval 6 heating method was applied, in which 50 mg dry sample is subject to a two-step, programmed pyrolysis (heating in an inert atmosphere) and oxidation heating cycle. During the pyrolysis step, the sample is heated to an iso-temperature of 300°C for 3 minutes and then ramped up (25°C min-1) to 650°C. The total concentration of the hydrocarbons and organic-derived fractions of CO, and CO2 that are released during the pyrolysis step (pyrolysable organic carbon wt% released from 300-650°C) are believed to constitute the “reactive organic carbon” content of the organic matter in a sample. The sample is then automatically transferred to the oxidation oven in which both the residual organic matter and mineral carbon are combusted between 400°C to 850°C. The “residual organic carbon” (RC wt.%) is the content of the residual organically-derived CO and CO2 during the oxidation heating stage. The reactive organic carbon represents the fraction of carbon that is released due to thermal decomposition kinetics of organic matter and hence is considered chemically reactive compared to the refractory “residual organic carbon”. The sum of the reactive organic carbon and residual organic carbon is equivalent to TOC.
TOC/N values in the Atacama trench core GeoB22908-2 were analyzed from freeze-dried homogenized sediment of each sampling interval. In brief, 3 g of the sediment was decalcified by the addition of 10 % HCl followed by repetitive washing steps with ultrapure water. For TOC/N determination, 10–30 mg of the dried sediment was weighed into tin capsules and analyzed via a Thermo Scientific Flash 2000 elemental analyzer connected to a Thermo Scientific Delta V Plus IRMS
Global data compilation of benthic data sets II
No full textIn this study we present a global distribution pattern and budget of the minimum flux of particulate organic carbon to the sea floor (J POC alpha). The estimations are based on regionally specific correlations between the diffusive oxygen flux across the sediment-water interface, the total organic carbon content in surface sediments, and the oxygen concentration in bottom waters. For this, we modified the principal equation of Cai and Reimers [1995] as a basic monod reaction rate, applied within 11 regions where in situ measurements of diffusive oxygen uptake exist. By application of the resulting transfer functions to other regions with similar sedimentary conditions and areal interpolation, we calculated a minimum global budget of particulate organic carbon that actually reaches the sea floor of ~0.5 GtC yr**-1 (>1000 m water depth (wd)), whereas approximately 0.002-0.12 GtC yr**-1 is buried in the sediments (0.01-0.4% of surface primary production). Despite the fact that our global budget is in good agreement with previous studies, we found conspicuous differences among the distribution patterns of primary production, calculations based on particle trap collections of the POC flux, and J POC alpha of this study. These deviations, especially located at the southeastern and southwestern Atlantic Ocean, the Greenland and Norwegian Sea and the entire equatorial Pacific Ocean, strongly indicate a considerable influence of lateral particle transport on the vertical link between surface waters and underlying sediments. This observation is supported by sediment trap data. Furthermore, local differences in the availability and quality of the organic matter as well as different transport mechanisms through the water column are discussed
Multibeam bathymetry raw data (Atlas Hydrosweep DS 2 echo sounder entire dataset) of RV METEOR during cruise M57/2
No full textMultibeam bathymetry raw data using the ship's own Atlas Hydrographic Hydrosweep DS 2 multibeam echo sounder was almost continuously recorded during RV METEOR cruise M57/2. Data was recorded on 27 days between 2003-02-11 and 2003-03-09. This dataset contains a elongated survey mostly 100 nautical miles of the Namibian coast. The approximate average depth of the entire dataset is around 2600m. Data analysis during data curation revealed that the data are partially of bad to very bad quality (especially in shallow areas), which is indicated in the parameter table.
The data are archived at the Federal Maritime and Hydrographic Agency of Germany (Bundesamt für Seeschifffahrt und Hydrographie, BSH) and provided to PANGAEA database for data curation and publication. No ancillary sound velocity profiles (SVP) from the cruise are archived at the BSH, thus no SVP added to this dataset. Whether SVP has been changed during the survey is unknown.
This publication is conducted within the efforts of the German Marine Research Alliance in the core area "Data management and Digitalization" (Deutsche Allianz Meeresforschung, DAM).
Data are unprocessed and therefore may contain incorrect depth measurements (artifacts) without further processing.
Data can be processed e.g. with the open source software package MB-System (Caress, D. W., and D. N. Chayes, MB-System: Mapping the Seafloor, http://www.mbari.org/products/research-software/mb-system/, 2021)
Sequential extraction of P components (SEDEX) in sediment core M157_41-03, off Namibia
No full textA 5-step sequential extraction scheme modified after Ruttenberg (1992), Schenau and De Lange (2000) and Küster-Heins et al., (2010) was used for the speciation of particulate P. Approximately 125mg freeze-dried sediment sample was successively washed with 25 ml of (1) 2 M NH4Cl (pH 7; 4 h; repeat 8 to 10 times), (2) CDB (citrate-dithionite-bicarbonate) buffer solution (pH 7.5; 8 h), (3) 1M sodium acetate buffer solution (pH 4; 6 h), (4) 1 M HCl (24 h) and (5) 1 M HCl (24 h) after ignition for 3 hours at 550 °C. The extracted P components include biogenic P in fish scales, bones and teeth that are mainly composed of hydroxyapatite (PHydap) from step 1, iron-bound P (PFe) from step 2, authigenic apatite (PAuthigenic) from step 3 typically corresponding to carbonate fluorapatite, detrital P (PDetrital) from step 4 and organic P (Porg) from step 5. The sum of these fractions gives the total P content (Ptotal). The P concentration of the solutions was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) with a precision of < 5 %
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