THIOSULFATE AND SULFITE DISTRIBUTIONS IN POREWATER OF MARINE-SEDIMENTS RELATED TO MANGANESE, IRON, AND SULFUR GEOCHEMISTRY

Depth distributions of thiosulfate (S2O32-) and sulfite (SO32-) were measured in the porewaters of a Danish salt marsh and subtidal marine sediments by HPLC analysis after derivatization with DTNP [2,2'-dithiobis(5-nitropyridine)]. The distributions were compared to the redox zonation as indicated by Eh and Mn2+, Fe2+, and H2S distributions. Concentrations Of S2O32- varied from below detection (<50 nM) to 600 nM while SO32- concentrations generally were 2-3 times higher, 100-1500 nM. Depth distributions of the two species were roughly similar. Lowest concentrations were found in the oxidized zone, including both the oxic surface layer and the suboxic zone of intense manganese and iron reduction, and concentrations tended to increase through the suboxic and into the reduced, sulfidic zone. The similarity of SO32- and S2O32- profiles suggested a close coupling of the cycling of the two species. Rates of consumption were suggested as the main factor governing their distribution. Rapid turnover times for S2O32- and H2S of 4 and 1. 1 h, respectively, were estimated for the upper 0-1 cm of a subtidal sediment.