title: Abundant porewater Mn(III) is a major component of the sedimentary redox system.
abstract: Soluble manganese(III) [Mn(III)] can potentially serve as both oxidant and reductant in one-electron-transfer reactions with other redox species. In near-surface sediment porewater, it is often overlooked as a major component of Mn cycling. Applying a spectrophotometric kinetic method to hemipelagic sediments from the Laurentian Trough (Quebec, Canada), we found that soluble Mn(III), likely stabilized by organic or inorganic ligands, accounts for up to 90% of the total dissolved Mn pool. Vertical profiles of dissolved oxygen and dissolved and solid Mn suggest that soluble Mn(III) is primarily produced via oxidation of Mn(II) diffusing upwards from anoxic sediments with lesser contributions from biotic and abiotic reductive dissolution of MnO2. The conceptual model of the sedimentary redox cycle should therefore explicitly include dissolved Mn(III).
authors: School of Marine Science and Policy, University of Delaware, Lewes, DE 19958, USA. andrew_madison@golder.com
authors: Andrew S
authors: AS
authors: Madison
authors: Bradley M
authors: BM
authors: Tebo
authors: Alfonso
authors: A
authors: Mucci
authors: Bjørn
authors: B
authors: Sundby
authors: George W
authors: GW
authors: Luther