The redox speciation of many biogeochemically important elements in seawater is found to be under strong kinetic control through reactions with oxygen and/or sulfide. This is most noticeably for iron and manganese, as the reduced species are more soluble than the corresponding higher oxidation states. In regions of low oxygen, significant concentrations of the reduced species can accumulate leading to changes in the distribution and residence times for these metals. Similarly Iodine speciation appears to be far from thermodynamic equilibrium in the ocean due to the facile reduction of iodate and the slow oxidation of iodide. In this presentation results from measurements of Fe, Mn and I speciation and kinetic reactivity during Meteor 90 (Nov 2012) along a North-South transect through the Oxygen Minimum Zone in the Eastern Tropical South Pacific will be shown and compared to early data along the same transect from 2008 (Meteor 77-4).

Importance of redox kinetics in the biogeochemical cycling of iron, manganese, and iodine in oxygen minimum zones

245th National Meeting (2013)

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