Seasonal Variations of soluble Organic-Fe(III) in Sediment Porewaters as Revealed by Voltammetric Microelectrodes

摘要

The seasonal cycling of iron and sulfur in the sediment from Rehoboth Bay (Delaware) was examined with solid state Hg/Au voltammetric microelectrodes. High resolution vertical profiles of ΣH_2S, Fe(II), and soluble organic-Fe(III) in the porewaters indicate that dissolved sulfide controls the fate of soluble organic-Fe(III). in the spring and in the fall, dissolved sulfide concentrations are negligible, and soluble Fe(III) and Fe(II) are dominant. This may be explained if the reduction of Fe(III) occurs by dissolution of solid Fe(III), then reduction to Fe(II), or if Fe(II) is oxidized anaerobically in the presence of organic ligands. During the summer, intensive sulfate reduction precipitates iron as FeS and pyrite. Because of its high reactivity and mobility, soluble organic-Fe(III) produced in porewaters can be considered a new reactive electron acceptor.