See Estes el al. (2019) for complete methods.
\nSediment slurries were generated by subsampling ~0.1 g of wet sediment from samples stored at 4 \u00b0C into a sterile microcentrifuge tube. Then, 0.2\u20130.5 ml of 0.2 \u03bcm filtered 18 M\u03a9 water was added
\nand the sample shaken. Sediment slurry (1\u201310 \u03bcl) was pipetted onto silicon wafers and air-dried. The beamline was operated with a 500 l mm\u20131 spherical grating monochromator and entrance and exit slits set to 40 \u03bcm, which yielded an absolute energy resolution of less than 0.3 eV. The samples were attached to an aluminium sample stick in a single load and analysed under ultrahigh vacuum conditions (pressure ~10\u22129 mbar). The measurements were made in the total electron yield (TEY) mode on a spot size of less than 1 mm2 using a grazing incidence angle
\nof 45\u00b0, where previous trials determined that the incidence angle did not yield a
\ndifference in results. The TEY mode was selected instead of fluorescence as we observed dampening of the fluorescence signal, probably due to matrix-induced absorption.
Spectra were collected around the C 1s edge, from 260 to 340 eV, with a dwell time of 0.2 s. To avoid beam damage and variation of the background due to charging, scans were taken at different positions on the sample. The spectra analysed were the average of 2\u20133 scans taken at different positions on the sample. The dark current was measured prior to the collection of each spectrum and subtracted from the raw data. Spectra were then normalized to no load current measured by a mesh upstream of the chamber with freshly evaporated gold.
\nInstruments:
\nBulk carbon NEXAFS spectroscopy was conducted on beamlines 8-2 and 10-1 at the Stanford Synchrotron Radiation Lightsource.
\nThe absolute energy calibration of the carbon spectra was achieved by shifting the energy such that the first dip in the incoming intensity due to carbon contamination on the beamline optics (carbon dip) occurred at 284.7 eV.
Carbon near edge X-ray absorption fine structure (NEXAFS) spectra from pelagic sediment from the North Atlantic gyre, South Pacific gyre, and Peru Basin from cruises KN223 (R/V Knorr), KNOX02RR\u00a0(R/V Roger Revelle), and ODP leg 201 between 2002 and 2014.\u00a0\u00a0
\nThese data were published in Estes et al. (2019).
\nThese data are available in two forms (see Data Processing Description section on this page for more information).
Spectral processing was completed by subtracting a line fit to the pre-edge region (281\u2013283 eV), followed by an area normalization between 282 and 310 eV with the high-energy intensity kept constant (atomic normalization). The entire pre-edge region appeared linear; fitting and background subtraction was conducted over a smaller energy range due to the presence of oxygen harmonic peaks. All the data normalization was conducted in Igor Pro (WaveMetrics).
\nBCO-DMO Data Manager Processing Notes:
\n* exported data in xlsx file \"Estes_bulkNEXAFSspectra_data.xlsx\" to csv file \"Estes_bulkNEXAFSspectra_data.csv\" which is available to download in the \"Data Files\" section of this page.\u00a0 The following changes were made after discussion with the original submitter.
\n* original data had 10 header rows with sample, and cruise information e.g. cruise_id, date, latitude, sample_depth, etc.\u00a0 The data were unpivoted so these values became new columns in the dataset.
\n* added a conventional header with dataset name, PI name, version date
\n* modified parameter names to conform with BCO-DMO naming conventions
\n* blank values in this dataset are displayed as \"nd\" for \"no data.\"\u00a0 nd is the default missing data identifier in the BCO-DMO system.
\n* latitude and longitude in degrees decimal minutes converted to decimal degrees then rounded to 5 decimal places.
\n* date format converted to ISO 8601 format yyyy-mm-dd
\n* added sample_comment column to capture the difference between the two columns with header information \"South Pacific;Knox02-RR;11-Jan-07;9;38\u00b0 03.7' S;133\u00b0 05.5' W;4924;piston;5.125\" in the original file (columns CE and CF in original data).
\n* data sorted by\u00a0{location}{expedition}{date}{latitude}{longitude}{water_depth}{core_type}{core_depth}{sample_comment}{eV}
\n* absorption values rounded to 5 decimal places