Stable isotopic signature of Dissolved Inorganic Carbon from surface underway samples collected during cruise AMT15
Originator's Protocol for Data Acquisition and Analysis
This data originates from analyses on samples collected from the ship's non-toxic supply each day around every 3-6 hours. Seawater samples were collected into glass collection bottles and preserved with mercuric chloride.
Total inorganic carbon was analyzed by manometry.
The stable carbon isotope enrichment in inorganic carbon in the water column was analysed using acidification and mass spectrometry (see Quay, Tilbrook and Wong, 1992). Seawater samples were collected and stored in pre-washed, baked (450°C) ground glass-stoppered bottles and then poisoned with HgCl 2 . CO 2 was extracted from the seawater samples by drawing the seawater sample into a gravimetrically calibrated burette, acidifying with phosphoric acid and stripping with 99.999% pure He at a flow rate of 40cm 3 min -1 for 30 minutes and collecting the CO 2 at -196°C after trapping out water at -70°C (the helium stripping technique). The d13C of the CO 2 gas was measured on a Finnigan MAT 251 mass spectrometer.
References Cited
Quay, P.D., Tilbrook, B., Wong, C.S., 1992. Oceanic uptake of fossil fuel CO2: Carbon-13 evidence, Science , 256, 74-79.
Instrumentation Description
Not applicable for this data set.
BODC Data Processing Procedures
Data were submitted via email in an Excel spreadsheet archived under BODC's accession number UWA060487. The data file received contained underway DIC and d13C data for cruises AMT15, AMT16 and AMT17. Sample metadata (Date, time (GMT), latitude, longitude and depth) were checked against information held in the database. The sampling times had been converted to GMT from local time in the file provided by the data originator. One discrepancy was noticed; the date of the sample taken on 29 September 2004 at 21.03 hours was incorrect when compared to the central navigation file and cruise report, so was changed to 28 September 2004.
The data were reformatted and marked up with BODC parameter codes and loaded into BODC's samples database under Oracle Relational Database Management System. For the following 3 samples the data contained repeat measurements; date: 11 October 2004, 15.00 hours, lat:-5.00°, lon:-25.00°; date: 12 October 2004, 09.05 hours, lat: -7.92°, lon: -25.00° and date: 13 October 2004, 04.00 hours, lat: -10.46°, lon: -25.00°. No DIC or d13C data values were obtained for these repeats so they were not loaded to the database. The sample taken on 12 October 2004 at 09.05 hours which also had repeat metadata did not have any data values but the metadata was loaded to the database for future reference. The sample taken on 26 September 2004, lat: 30.20°, lon: -18.98°, had no values reported so was not loaded to the database.
The stable carbon isotope data were provided in parts per thousand (per mille) quoted relative to the Pee Dee Belemnite standard (PDB). The total dissolved inorganic carbon concentration data were provided in micro grams per kilogram. These units were consistent with the BODC parameter code units and no conversions were applied.
A parameter mapping table is provided below;
Originator's Parameter | Units | Description | BODC Parameter Code | Units | Comments |
---|---|---|---|---|---|
DIC Conc. (µmol/kg) | µmol/kg -1 | Concentration of carbon (total inorganic) {TCO2} per unit volume of the water body [dissolved plus reactive particulate phase] by manometry | TCO2MATX | µmol/l -1 | n/a |
Delta 13C (per mille PDB) | ‰ (PDB) | Enrichment of 13C in inorganic carbon in the water body [dissolved plus reactive particulate phase] by acidification and mass spectrometry | D13CMITX | ‰ (PDB) | n/a |
Data Quality Report
BODC was advised by the data originator of a number of quality issues with the data and these data points were flagged 'L' within the database.
Problem Report
Not relevant to this data set.