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Biogeochemical cycling in an organic-rich coastal marine basin. 8. A sulfur isotopic budget balanced by differential diffusion across the sediment-water interface

Geochimica et Cosmochimica Acta
By: , , and 
https://doi.org/10.1016/0016-7037(87)90212-2

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Abstract

The sulfur isotopic composition of the sulfur fluxes occurring in the anoxic marine sediments of Cape Lookout Bight, N.C., U.S.A., was determined, and the result of isotopic mass balance was obtained via the differential diffusion model. Seasonal pore water sulfate δ34S measurements yielded a calculated sulfate input of 0.6%.. Sulfate transported into the sediments via diffusion appeared to be enriched in the lighter isotope because its concentration gradient was steeper, due to the increase in the measured isotopic composition of sulfate with depth. Similarly, the back diffusion of dissolved sulfide towards the sediment-water interface appeared enriched in the heavier isotope. The isotopic composition of this flux was calculated from measurements of the δ34S of dissolved sulfide and was determined to be 15.9%.. The isotopic composition of buried sulfide was determined to be −5.2%. and the detrital sulfur input was estimated to be −6.2%.. An isotope mass balance equation based upon the fluxes at the sediment-water interface successfully predicted the isotopic composition of the buried sulfur flux within 0.5%., thus confirming that isotopes diffuse in response to their individual concentration gradients.

Publication type Article
Publication Subtype Journal Article
Title Biogeochemical cycling in an organic-rich coastal marine basin. 8. A sulfur isotopic budget balanced by differential diffusion across the sediment-water interface
Series title Geochimica et Cosmochimica Acta
DOI 10.1016/0016-7037(87)90212-2
Volume 51
Issue 5
Year Published 1987
Language English
Publisher Elsevier
Description 8 p.
First page 1201
Last page 1208
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