Dataset: pFe concentrations and isotopes of GP17-OCE

Sample source and treatment

Total phase

An aliquot (0.5 mL) of the total digest described in Ohnemus et al. (2015) were provided by D. Ohnemus and M. Ricci. Aliquots of the leachate containing a known quantity of Fe were then spiked with an Fe-57-Fe-58 double-spike and purified by anion exchange chromatography and Fe concentration and d⁵⁶Fe were measured by Thermo Neptune Plus multi-collector ICP-MS.

 

Labile phase

A subsample of 0.8 - 51 um-sized suspended particles collected using McLane in situ pumps on the GP17-OCE cruise was provided by D. Ohnemus. Details of the sampling methodology are described in Ohnemus & Lam (2015). For a small number of samples, a low volume of seawater drawn through the filter resulted in unreliable data (see Data Processing).

The "labile" phase of the suspended particles was determined by leaching with a pH 8 solution of 0.1M oxalic acid and 0.05M EDTA for 2 hours at 90 C. Method is described in Revels et al (2015). Concentrations of Fe in the labile phase were determined by analysis of the leachate on an Agilent 8900 QQQ ICPMS. Samples were run alongside blanks and standards prepared in the same matrix, with all samples, blanks and standards spiked with In as an internal standard. Repeat analyses of blanks and standards were carried out throughout analysis sequences as a further check on instrumental drift and reproducibility of data.

Aliquots of the leachate containing a known quantity of Fe were then spiked with an Fe-57-Fe-58 double-spike and purified by anion exchange chromatography and Fe concentration and d⁵⁶Fe were measured by Thermo Neptune Plus multi-collector ICP-MS. The method is fully described in Revels et al (2015).

 

References:

D.C. Ohnemus and P.J. Lam (2015) Cycling of lithogenic marine particles in the US GEOTRACES North Atlantic transect. Deep-Sea Research II 116, 283-302. doi:10.1016/j.dsr2.2014.11.019
B.N. Revels, D.C. Ohnemus, P.J. Lam, T.M. Conway, S.G. John (2015) The isotopic signature and distribution of particulate iron in the North Atlantic Ocean. Deep-Sea Research II 116, 321-331. doi:10.1016/j.dsr2.2014.12.004