Samples were filtered, acidified, and split at sea. Samples were collected by Niskin bottle and the towed GeoFish. Refer to the EPZT cruise report\u00a0for more information on cruise operations (http://dmoserv3.whoi.edu/data_docs/GEOTRACES/EPZT/GT13_EPZT_ODFReport_All.pdf).\u00a0
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We prepared our 5L split for neodymium isotopic analysis following Shabani et al. (1992). Samples were pH-adjusted to pH ~3.5, then pumped through 300 \u00b5l of HDEHP in a C18 cartridge to capture REEs. Rare earth elements were eluted from the cartridge using 6M HCl, then Nd was isolated using sequential chromatographic columns: AG50-X8 (BioRad) and Ln-Spec (Eichrom). Neodymium isotopic measurements were made at Lamont-Doherty Earth Observatory (Palisades, NY) using a Thermo Neptune multicollector ICP-MS.
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For REE concentrations we removed an aliquot after pH-adjustment of each sample. Sample methodology is described in Behrens et al. (2006), as Lab #3. We preconcentrated 20 ml of sample offline using a SeaFast PICO system (ESI), then analysed the resulting solution at Oregon State University (Corvallis, OR) using a Thermo X-Series II ICP-MS.
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Problem Report: Cerium measurements yielded questionable data during a couple of run days, these data are indicated using IODE quality flag 3\u2013 Questionable Data. Sample gaps in REE concentrations are due to analytical error during pre-concentration, sample gaps in Nd isotope data are due to insufficient quantity of Nd to make a measurement.
Neodymium isotope ratios were corrected using JNdi-1 standard for reference (Tanaka et al., 2000). Dissolved concentrations were determined by external calibration. Calibration standards were diluted by weight and pre-concentrated using the same method as the samples. To account for evaporation we included pre-concentrations of an in-house REE consistency standard at regular intervals. Validation of the correction was done by additional pre-concentrations and measurements of two in-house seawater samples, one from Bransfeld Strait (~1100m depth) and one from nearshore California (~surface depth).
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IODE Quality Flag Codes:
\nGood quality = 1
\nNot evaluated, not available, or unknown quality = 2
\nQuestionable/suspect quality = 3
\nBad quality = 4
\nMissing data = 9