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Couture, R. M., University of Waterloo, Waterloo, Canada, raoul.couture@uwaterloo.ca
Van Cappellen, P., University of Waterloo, Waterloo, Canada, pvc@uwaterloo.ca
Fisher, R., University of Waterloo, Waterloo, Canada, r3fisher@uwaterloo.ca
Campisi, D., Université du Québec INRS-ETE, Québec, Canada, diego.campisi@ete.inrs.ca
Gobeil, C., Université du Québec INRS-ETE, Québec, Canada, charles.gobeil@ete.inrs.ca

REACTIVE-TRANSPORT MODELING OF THE SULFUR CYCLE IN LAKE SEDIMENTS: FIXING THE LEAKS

Current reactive-transport models for the early diagenesis of sulfur (S) coupled to the microbial degradation of organic matter (OM) in lake sediments generally consider only sulfate (SO4) reduction and iron sulfides formation. They neglect the pools of organic oxidized (e.g., ester-SO4) and reduced (e.g., sulfidized OM) S, despite the evidence that these pools can dominate sedimentary S speciation [1]. Similarly, dissolved zero-valent S (S0 (aq)), a key redox-active species, is often included in the reaction set but not accounted for in the reactive-transport equations, resulting in “leaky” models [2]. Here, we build on an existing biogeochemical simulation module for MATLAB® ([3]) to study the vertical distribution of three pore water (SO4, S0 (aq) and HS-) and five solid phase S species (elemental sulfur, iron monosulfide, pyrite, ester-SO4, and sulfidized OM) in lake sediments. The code, which includes a representation of the effect of benthic macro-fauna on S cycling, and allows non-steady state boundary conditions, is calibrated against a dataset on solid-phase S speciation acquired through a combination of sequential extractions and X-ray near-edge absorption spectroscopy (XANES). [1] Urban NR et al. (1999) Geochim. Cosmochim. Acta 63, 837-853. [2] Meysman FJR and Middelburg JJ (2005) Mar. Chem. 97, 206-212. [3] https://sites.google.com/site/biogeomatlab/

Oral presentation

Session #:SS34
Date: 7/09/2012
Time: 17:45