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description:
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This data layer comprise organic carbon and nitrogen concentrations and isotopes and specific surface areas of the mud fraction (less than 63 um) of the upper 2 cm of seabed sediments.
Bottom sediments were collected using either a Smith McIntyre grab or Box Core. The upper ~0-2 cm of seabed sediment was spooned into a bag for the purpose of grainsize analysis. The less than 63um sieve fraction was freeze-dried, ground in a tungsten carbide mill and decarbonated. The decarbonated powders were sent to Environmental Isotopes Pty Ltd (Sydney) for isotopic analysis by mass spectrometry. Samples were back-corrected to account for the carbonate removal, using carbonate concentrations derived from the bomb method. Specific surface areas were determined using a 5-point Brunauer-Emmett-Teller (BET) adsorption isotherm on a Quantachrome NOVA 2200e analyser, with nitrogen used as the adsorbate. The samples were first cleaned of organic matter by slow heating for 12 hours to 350oC. Error estimates for the C and N isotope values are ±0.15. The carbonate measurements (used to back correct) were better than 5%. The average RSD of the specific surface area measurements was 7.5%. |