1. δ 56 Fe – Motivation GA10 Samples & Planned Work We have deep water profiles from the trace metal casts For JC068 we have stations 8, 11, 12, 13, 16, 18 and 21 For D357 we have stations 3, 6, 11/4.5 and 8/0.5 No isotope measurements yet, but as soon as we have Fe concentration (hopefully complete Fe isotope measurements early next year) To understand processes and cycling of Fe in the ocean in a way that is not always possible with Fe concentration alone. To fingerprint the different sources of Fe and constrain their various importance, their impact on the ocean, and how Fe is cycled through the ocean. Tim Conway and Seth John Marine Trace Element Lab, University of South Carolina

2. δ 56 Fe – What do we know? A. Santa Monica Basin E. North Atlantic D. Eq. Pacifc C. S. Ocean B. San Pedro Basin Sediments Hydrothermal Venting?? Dust Sediments Biological remineralization Dust (John et al., 2012; Lacan et al., 2008; Radic et al, 2011; John and Adkins, 2012) Fe sources appear to have distinctive signatures : Aerosol Dust is slightly +ve – from 0.1 to perhaps 0.5 ‰ ? Crustal Fe 0.07 ‰ (Poitrasson, 2006), rivers (-0.6 to 0.3 ‰; Radic et al., 2011) Fe(II) from reducing sediments is very –ve (as much as -3 ‰; John and Adkins) Hydrothermal complicated? Biological fractionation is currently relatively unconstrained (heavy?) δ 56 Fe (‰)

3. Method for dissolved δ 56 Fe, δ 114 Cd and δ 66 Zn We have developed a new method to measure δ 56 Fe, δ 114 Cd and δ 66 Zn simultaneously in small volumes of seawater (1-2 L). Metals are extracted onto Nobias PA-1 chelating resin, eluted, then purified using AGMP-1 ion-exchange resin. This generates low blank, high extraction efficiency and effective purification of each element from salts/interference (e.g. Ni, Cr). Analysis is by Neptune MC ICP-MS using a Jet interface (HR for Fe, Zn; LR for Cd). 57 Fe- 58 Fe, 110 Cd- 111 Cd, 64 Zn- 66 Zn double spikes allow correction for IMB. Fe Zn Cd Fe Zn Cd Procedural BlankExtraction EfficiencyColumn Purification CdFe Salts ZnCu ng

4. Fe Isotopes from GA-03 (Eastern North Atlantic) [Fe] (nM)δ 56 Fe (‰) Depth (m) [Fe] (nM) δ 56 Fe (‰) Both stations exhibit similar patterns IRMM-14 Fe St. 9 St. 10 Tim Conway and Seth John Marine Trace Element Lab, University of South Carolina Several hypothesized features visible: 1. Dust input (+0.5-0.8 ‰) 2. Biological uptake of heavy Fe 3. Deep sedimentary input of light Fe 1 2 3 3 2 1 IRMM-14 Fe

5. Tim Conway and Seth John Marine Trace Element Lab, University of South Carolina Cd Isotope and concentration profiles reflect nutrient uptake and remineralisation : 1.Low concentration and high δ 114 Cd at surface 2.Deep water δ 114 Cd stable at 0.3 - 0.4 ‰ NIST 3108 Cd [Cd] (pM) δ 114 Cd (‰)[Cd] (pM)δ 114 Cd (‰) NIST 3108 Cd St. 9 St. 10 Depth (m) Cd Isotopes from GA-03 (Eastern North Atlantic) 1 1 2 2