The iron “redox battery” in sandy sediments: Its impact on organic matter remineralization and phosphorus cycling

• DOI: 10.1016/j.scitotenv.2022.161168
• Publication Date: 2022-12-23T16:03:13Z
• Authors: Zhe Zhou; Susann Henkel; Sabine Kasten; Moritz Holtappels
• Keywords: Biogeochemical Cycle; Authigenic; Cycling

Permeable sandy sediments cover 50-60 % of the global continental shelf and are important bioreactors that regulate organic matter (OM) turnover nutrient cycling in coastal ocean. In sands, dynamic porewater advection can cause rapid mass transfer variable redox conditions, thus affecting OM remineralization pathways, as well recycling iron phosphorus. this study, North Sea sands were incubated flow-through reactors (FTRs) to investigate biogeochemical processes under changing conditions. We found average rate anaerobic was 12 times lower than aerobic pathway, Fe(III) oxyhydroxides be major electron acceptors during 34 days anoxic incubation. Reduced Fe accumulated solid phase (expressed Fe(II)) before significant release Fe2+ into porewater, most reduced (~96 %) remained throughout Fe(II) retained phase, either through formation authigenic Fe(II)-bearing minerals or adsorption, easily re-oxidized upon exposure O2. Excessive P (apart from remineralization) started at beginning incubation accelerated after with a constant P/Fe2+ ratio 0.26. After incubation, re‑oxygenated > 99 released coprecipitated oxidation (so-called "Fe curtain"). Our results demonstrate Fe(III)/Fe(II) serve relatively immobile rechargeable "redox battery" advection. This is characteristic for permeable environments making an player turnover. also suggest liberated escape curtain" surface sediments, potentially increasing net benthic efflux