Annual fluctuations in sulfur isotope fractionation in the water column of a euxinic marine basin |
| |
Authors: | Ketil B Sørensen Donald E Canfield |
| |
Institution: | 1 12-7 Venable Hall CB 3300, Marine Sciences Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3300, USA 2 Danish Center for Earth System Science, Institute of Biology, University of Southern Denmark, Campuvej 55, 5230, Odense M, Denmark |
| |
Abstract: | The sulfur cycle of Mariager Fjord was studied by following the pool of sulfide in the anoxic water and its isotopic composition during a period of 3 yr. Though most of the sulfide accumulating in the fjord was formed in the sediment, the isotopic composition of sulfide in the water was different from the isotopic composition of sulfide diffusing into the water from the sediment. The mean isotopic composition of the water column sulfide (δ34S) varied during the year between −13‰ and −21‰ with the most negative values reached during winter/early spring, while the sulfide diffusing into the water from the sediment had a mean isotope composition of −11.3‰. This annual pattern suggested that processes in the oxidative part of the sulfur cycle were responsible for the excess fractionation, and mass-balance considerations indicated that the excess fractionation of the sulfur isotopes could be accounted for by disproportionation of S0 or S2O32− in the water column, but not by water column sulfate reduction or sulfide oxidation alone. MPN counts demonstrated that a population of more than 3 × 104 cells mL−1 capable of growing by disproportionation of these two substrates was present in all depths of the fjord. The results presented in this communication demonstrate that the isotopic depletion of sulfide in anoxic systems may vary between periods of net sulfate reduction versus periods of net sulfide oxidation and indicate that disproportionation of sulfur compounds may be an important step in the sulfur cycle of euxinic basins. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|