Dataset: Dissolved concentrations and stable isotope ratios of Fe, Zn, and Cd from Leg 2 (Hilo, HI to Papeete, French Polynesia) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1815) on R/V Roger Revelle from October to November 2018

Final no updates expectedDOI: 10.26008/1912/bco-dmo.884673.1Version 1 (2022-12-06)Dataset Type:Cruise Results

Principal Investigator: Timothy M. Conway (University of South Florida)

Co-Principal Investigator: Seth G. John (University of Southern California)

Scientist: Matthias Sieber (University of South Florida)

BCO-DMO Data Manager: Shannon Rauch (Woods Hole Oceanographic Institution)


Program: U.S. GEOTRACES (U.S. GEOTRACES)

Project: US GEOTRACES Pacific Meridional Transect (GP15) (U.S. GEOTRACES PMT)

Project: Collaborative research: US GEOTRACES PMT: Trace-metal concentrations and stable isotopes in the North Pacific (PMT TM Stable Isotopes)


Abstract

This dataset reports dissolved (0.2µm AcroPak filter) concentrations and stable isotope ratios of iron, zinc, and cadmium (Fe, Zn, and Cd) via Nobias PA-1 extraction and MC-ICPMS analysis in water samples collected by the GTC (GEOTRACES Trace-metal clean CTD carousel) and/or surface tow fish from 23 stations along the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15) on R/V Roger Revelle from October to November 2018. The GP15 cruise sailed from September to November 2018 on a meridio...

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Seawater samples were collected using the GEOTRACES trace-metal clean sampling system (rosette with 24 12-liter GO-FLO bottles) or a towfish for surface samples (Cutter and Bruland, 2012). Samples were filtered through acid-cleaned AcroPak capsule filters (0.2 micrometers (μm)) into acid-cleaned LDPE bottles. For concentration and isotope analysis at the University of South Florida (USF), 2 liters of filtered seawater were collected, acidified ashore at USF by addition of 2.4 milliliters (mL) 10 molar (M) Teflon-distilled HCl, and stored for at least 12 months at pH ∼2 before processing.

Seawater samples were processed for isotope analysis following Sieber et al. (2019). Briefly, a double-spike for cadmium (Cd), iron (Fe), and zinc (Zn) was added prior to batch extraction using Nobias PA-1 chelating resin, followed by purification by anion-exchange chromatography using AG-MP1 resin. Isotope analyses were performed on a Thermo Neptune Plus MC-ICPMS in the Tampa Bay Plasma Facility at the University of South Florida using an Apex-Q (Cd) or Apex Ω (Fe, Zn) introduction system.

We express Cd stable isotope ratios in delta notation (δ114Cd) relative to the NIST SRM-3108 Cd standard. A secondary standard, BAM-I012, was analyzed over 8 sessions on the same timescale as the samples to provide an estimate of long-term instrumental precision. We obtain a value of −1.32 ± 0.06‰ (2SD, n = 172), in agreement with consensus values (Abouchami et al., 2013). Using the 2SD of offsets from the mean of full replicate measurements based on 26 pairs of replicate analysis on separate seawater samples collected at the same depth (the GP15 sampling strategy collected overlapping samples between casts), we obtain a second estimate of external precision (0.05‰), which is similar to analytical precision. Therefore, we consider a 2SD uncertainty of 0.06‰ as a conservative estimate of analytical precision, and have applied it to all samples, except for low-concentration samples where the larger internal error is considered a more conservative estimate of uncertainty. Concentrations were calculated using the isotope dilution technique based on on-peak blank, interference and mass-bias corrected 114Cd/111Cd ratios measured simultaneously with isotope analyses (Sieber et al., 2019). We express uncertainty (1SD) on Cd concentrations as 2%, based on replicate analysis on separate seawater samples collected at the same depth (n = 26).

We express Fe stable isotope ratios in delta notation (δ56Fe) relative to the IRMM-014 standard. A secondary Fe standard, NIST-3126, was analyzed over 44 sessions to provide an estimate of long-term instrumental precision. We obtain a value of +0.36 ± 0.05‰ (2SD, n = 604), in agreement with consensus values (Conway et al., 2013). As a second estimate of external precision, we use the 2SD of offsets from the mean of full replicate measurements based on 26 pairs of replicate analysis using separate seawater samples collected at the same depth (0.08‰), which is similar to the analytical precision. Therefore, we consider a 2SD uncertainty of 0.05‰ as an estimate of analytical precision, and have applied it to all samples, except for low-concentration samples where the larger internal error is considered a more conservative estimate of uncertainty. Concentrations were calculated using the isotope dilution technique based on on-peak blank, interference and mass-bias corrected 57Fe/56Fe ratios measured simultaneously with isotope analysis. We express uncertainty (1SD) on Fe concentrations as 2%, based on replicate analysis on separate seawater samples collected at the same depth (n = 26).

We express Zn stable isotope ratios in delta notation (δ66Zn) relative to the JMC-Lyon standard. A secondary Zn standard, AA-ETH, was analyzed on the same timescale as the samples (over 10 sessions) to provide an estimate of long-term instrumental precision. We obtain a value of +0.28 ± 0.03‰ (2SD, n = 147), in agreement with consensus values (Archer et al., 2017). As a second estimate of external precision, we use the 2SD of offsets from the mean of full replicate measurements based on 26 pairs of replicate analysis using separate seawater samples collected at the same depth (0.03‰), which is similar to the analytical precision. Therefore, we consider a 2SD uncertainty of 0.03‰ as an estimate of analytical precision, and have applied it to all samples, except for low-concentration samples where the larger internal error is considered a more conservative estimate of uncertainty. Concentrations were calculated using the isotope dilution technique based on on-peak blank, interference and mass-bias corrected 67Zn/66Zn ratios measured simultaneously with isotope analysis. We express uncertainty (1SD) on Zn concentrations as 5%, based on replicate analysis on separate seawater samples collected at the same depth (n = 26).


Related Datasets

Continues

Dataset: GP15 Fe Zn Cd Dissolved and Stable Isotope Ratios - Leg 1
Relationship Description: GP15 was made up of two cruise legs, RR1814 (Leg 1) and RR1815 (Leg 2).
Conway, T. M., John, S. G., Sieber, M. (2022) Dissolved concentrations and stable isotope ratios of Fe, Zn, and Cd from Leg 1 (Seattle, WA to Hilo, HI) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1814) on R/V Roger Revelle from September to October 2018. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2022-12-06 doi:10.26008/1912/bco-dmo.883862.1

Related Publications

Methods

Abouchami, W., Galer, S. J. G., Horner, T. J., Rehkämper, M., Wombacher, F., Xue, Z., Lambelet, M., Gault-Ringold, M., Stirling, C. H., Schönbächler, M., Shiel, A. E., Weis, D., & Holdship, P. F. (2012). A Common Reference Material for Cadmium Isotope Studies - NIST SRM 3108. Geostandards and Geoanalytical Research, 37(1), 5–17. https://doi.org/10.1111/j.1751-908x.2012.00175.x
Methods

Archer, C., Andersen, M. B., Cloquet, C., Conway, T. M., Dong, S., Ellwood, M., Moore, R., Nelson, J., Rehkämper, M., Rouxel, O., Samanta, M., Shin, K.-C., Sohrin, Y., Takano, S., & Wasylenki, L. (2017). Inter-calibration of a proposed new primary reference standard AA-ETH Zn for zinc isotopic analysis. Journal of Analytical Atomic Spectrometry, 32(2), 415–419. https://doi.org/10.1039/c6ja00282j
Methods

Conway, T. M., Rosenberg, A. D., Adkins, J. F., & John, S. G. (2013). A new method for precise determination of iron, zinc and cadmium stable isotope ratios in seawater by double-spike mass spectrometry. Analytica Chimica Acta, 793, 44–52. doi:10.1016/j.aca.2013.07.025
Methods

Cutter, G. A., & Bruland, K. W. (2012). Rapid and noncontaminating sampling system for trace elements in global ocean surveys. Limnology and Oceanography: Methods, 10(6), 425–436. doi:10.4319/lom.2012.10.425
Methods

Sieber, M., Conway, T. M., de Souza, G. F., Obata, H., Takano, S., Sohrin, Y., & Vance, D. (2019). Physical and biogeochemical controls on the distribution of dissolved cadmium and its isotopes in the Southwest Pacific Ocean. Chemical Geology, 511, 494–509. doi:10.1016/j.chemgeo.2018.07.021