Jackson Estuarine Laboratory

Evidence for organically associated iron in nearshore pore fluids


The role of dissolved organic matter (DOM) in the speciation of trace metals in natural waters is poorly understood1–3. Although dissolved organic matter–iron associations have been observed in freshwater systems4–6, it has been thought that DOM–iron species are not significant in saline waters7. Yet recent studies have suggested that iron–DOM interactions in the pore waters of anoxic marine sediments may be important8,9. The possibility of organically associated trace metals in anoxic water has been used to explain why metal concentrations are higher than those predicted by sulphide-mineral equilibria10,11. We present here data that indicate that strong iron–DOM associations do occur in the anoxic pore waters of nearshore marine sediments and that both the total dissolved iron and organically associated iron change seasonally.

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