Isotope Analyses

Seawater samples were collected for stable isotopic analysis by rinsing, then filling 125-mL bottles such that no headspace remained. Samples were fixed with 50 microliters (µL) of saturated mercuric chloride, and sealed with Teflon crimp caps containing a thin coating of Apiezon grease. Samples were refrigerated during storage prior to analysis. Analyses were completed at the University of South Florida Department of Geology Stable Isotope Laboratory using a Thermo-Finnigan Delta V 3 kiloelectron (keV) Isotope Ratio Mass Spectrometer coupled to a GasBench II preparation device. Analyses of d18O of H2O was completed by equilibrating 200 µL of sample with approximately 12 mL headspace of H2 in septum-capped vials. After equlibration, the isotopic composition of the headspace gas was measured (methods following Epstein and Mayeda, 1953; Prosser and Scrimgeour, 1995). Analyses of δ13C of dissolved inorganic carbon (DIC) was completed by injecting 1 mL of sample into an approximately 12-mL vial that was pre-flushed with He and pre-filled with 1 mL of 85 percent H3PO4 (methods following Assayag and others, 2006). The CO2 produced by this acid-stripping of the DIC was then measured after 24 h of equilibration. All stable isotope data are expressed in the conventional delta (d) notation:

Δ = [(Rsample-Rstandard)/Rstandard] × 1000‰

where Rsample and Rstandard is the 18O/16O ratio of the sample and standard, respectively, for d18O. The standard used as a reference for the d scale is VSMOW for H2O. Internal standards were used in the calibration to the VSMOW scale (VEEN and HTAMP waters with d18O = -13.17 per mil (‰) and +15.05‰) and PDB scale Carrara Marble and NBS-18 calcite). Analytical precision on these standards was better than 0.15‰ for d18O and 0.2‰ for d13C.

The QA/QC process compared analysis results with calibrated reference standards

For aditional information see:
HLY1202 Cruise Report, Appendix E
U.S. Geological Survey Data Series 862 - Methods
USFSI Stable Isotope Lab

BCO-DMO Processing Notes
- Generated from original file: "HLY1202_Isotopes.csv" contributed by Lisa Robbins
- Parameter names edited to conform to BCO-DMO naming convention found at Choosing Parameter Name
- Date reformatted from MM/DD/YYYY to YYYYMMDD
- Time reformatted from HH:MM to HHMM
- "nd" (no data) inserted into blank fields