Dépôt numérique
RECHERCHER

Non-steady state diagenesis of organic and inorganic sulfur in lake sediments.

Couture, Raoul-Marie; Fischer, Rachele; Van Cappellen, Philippe; Gobeil, Charles (2016). Non-steady state diagenesis of organic and inorganic sulfur in lake sediments. Geochimica et Cosmochimica Acta , vol. 194 . p. 15-33. DOI: 10.1016/j.gca.2016.08.029.

Ce document n'est pas hébergé sur EspaceINRS.

Résumé

Sulfur controls the fate of many geochemical elements in lake sediments, including iron, phosphorus and environmentally important trace elements. We measured the speciation of pore-water and sediment-bound sulfur (aqueous sulfate and sulfides, elemental sulfur, iron monosulfide, pyrite, organic sulfur) and supporting geochemical variables (carbon, oxygen, iron) in the sediments of a perennially oxygenated and a seasonally anoxic basin of an oligotrophic lake in Québec, using a combination of pore-water analyses, sequential extractions and X-ray absorption near edge structure. A non-steady state early diagenetic model was developed and calibrated against this extensive dataset to help unravel the pathways and quantify the rates of S transformations. Results suggest that the main source of S to the sediments is the settling of organic ester-sulfate (R-O-SO₃-H). Hydrolysis of these compounds provides an additional source of sulfate for anaerobic microbial oxidation of sedimentary organic matter, releasing sulfide to the pore-water. Reduced solid-bound S species accumulate as thiols (R-SH) and iron sulfides in the perennially oxygenated and seasonally anoxic basin, respectively. The model-estimated rate constant for R-SH formation is lower than previously estimated for this particular lacustrine site, but similar to that proposed for marine shelf sediments. The solid sediment S profiles, however, carry the imprint of the time-dependent sulfate input to the lake. Iron sulfide enrichments formed during past decades of elevated atmospheric SO₄ deposition are presently dissolving. In the sediments of the perennially oxygenated basin this reaction hampers the build-up of Fe(III) (oxy)hydroxide near the sediment–water interface.

Type de document: Article
Mots-clés libres: sulphur; organosulfur compounds; iron sulphides; early diagenetic modeling; seasonal anoxia; oligotrophic lakes; X-ray absorption spectroscopy
Centre: Centre Eau Terre Environnement
Date de dépôt: 04 mai 2018 19:26
Dernière modification: 04 mai 2018 19:26
URI: http://espace.inrs.ca/id/eprint/5660

Actions (Identification requise)

Modifier la notice Modifier la notice