Lecture Chemical Speciation in the Oceans (and beyond) 1

Some general paper/proposal topic areas Specific geochemistry of element(s) Particular sources/sinks (rivers, dust, hydrothermal, groundwater or sedimentary) Influences of metal(s) on primary productivity or other biological processes Paleoclimate (Cd Zn other tracers in biominerals) Ancient Ocean/Co-Evolution of Ocean Chemistry and Life Analytical approaches Specific metalloenzyme(s) and the relationship(s) to biogeochemical function/processes Policy of iron fertilization and other climate mitigation proposals Aspects of marine pollution Redox processes Aspects of metal toxicology Application of Modeling Studies to trace metal biogeochemistry 2

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Speciation is also critical to the intracellular environment 4

Inorganic Analytical Approaches Graphite Furnace Atomic Absorption Spectroscopy (GF-AAS) – Older technique, often coupled with solvent extraction, not used as much anymore Inductively Coupled Plasma Mass Spectrometry (ICP-MS) – Quadrapoles, high resolution magnetic sector, multicollector Flow Injection/Chemiluminescence/Spectrophotometry Electrochemistry (Voltammetry) HPLC Electrospray ionization mass spectrometry (organic molecule component of complex) 5

Types of Electrochemical Analyses Cathodic Stripping Voltametry (Fe, Co, Ni, Zn, Cu) – Hanging Mercury Drop Electrode (CSV-HMDE) – Preconcentrates using adsorption of a metal-L synthetic complex – Reduces the metal (and in some cases the ligand) to generate signal e.g. -0.6V to -1.4 V Anodic Stripping Voltametry (Zn, Cd, Pb) – Thin Film Mercury Rotating disk electrodes (ASV TF-RDE) – Preconcentrates using adsorption of elemental metal holding a reduction potential – No synthetic Ligand needed – Oxidizes the metal to achieve signal e.g to -0.4 V 6

Calibration of the Synthetic Ligand with EDTA 7

Kinetics of Competitive Ligand Exchange A = +Fe B = + SA C begin analysis L’ = unbound ligand 8

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To actually calculate ligand concentrations, and K cond titration data is analyzed using Scatchard plots or van den Berg/Ruzic plot, or non-linear fitting 12

Morel, Allen, Saito, Treatise on Geochemisrty

From Vraspir and Butler

Bruland

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From Buck and Bruland 2007 The physiochemical speciation of dissolved iron in the Bering Sea, Alaska Limnol Oceanogr, 2007 “These observations suggest that the phytoplankton community is readily able to access dissolved Fe from the FeL 1 complex, resulting in excess L 1 between dissolved Fe and L 1 ligand concentrations in samples with intermediate dissolved Fe, and this is a seemingly ubiquitous feature of dissolved Fe cycling in the marine environment.” FeL 1 as a nutritional source? How do phytoplankton acquire iron and other bioactive metals? 20

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In culture, copper ligands are produced by cyanobacteria Moffett and Brand, Limnol Oceanogr,

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Cobalt ligands in seawater have a biological source (Production of ligands in a Synechococcus feature in the Costa Rica Upwelling Dome Saito et al., Limnol Oceanogr 2005) 24

Competition between metals for ligands Nickel affinity > Cobalt Nickel is also much more abundant than cobalt (from Saito and Moffett, 2001) How can CoL exist? Turns out it is Co(III)L 25 K CoL

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LC-MS Detection of siderophores in seawater (nutrient enriched incubations) Gledhill et al., Marine Chemistry

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