title: Iron traps terrestrially derived dissolved organic matter at redox interfaces.
abstract: Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 ± 7% (mean ± SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters.
authors.affiliation: Institut für Geoökologie, Technische Universität Braunschweig, 38106 Braunschweig, Germany. thomas.riedel@tu-bs.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Riedel
authors.forename: Dominik
authors.initials: D
authors.lastname: Zak
authors.forename: Harald
authors.initials: H
authors.lastname: Biester
authors.forename: Thorsten
authors.initials: T
authors.lastname: Dittmar
mesh_terms: D001419:Bacteria / Q000378:metabolism; D057486:Carbon Cycle / Q000502:physiology*; D057965:Carbon Sequestration / Q000502:physiology*; D005227:Fatty Acids / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D062385:Hydroxybenzoates / Q000737:chemistry*; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D012623:Seawater / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D053833:Wetlands
chemical_list: D005227:Fatty Acids; D006841:Hydrocarbons, Aromatic; D062385:Hydroxybenzoates; D012987:Soil; D007501:Iron; C017616:phenolic acid; D010100:Oxygen
keywords: carbon cycle; carbon sequestration; phenolics; wetland restoration