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 m easured in the porewaters of a Danish salt marsh and subtidal marine s ediments by HPLC analysis after derivatization with DTNP [2,2'-dithiob is(5-nitropyridine)]. The distributions were compared to the redox zon ation as indicated by Eh and Mn2+, Fe2+, and H2S distributions. Concen trations Of S2O32- varied from below detection (<50 nM) to 600 nM whil e SO32- concentrations generally were 2-3 times higher, 100-1500 nM. D epth distributions of the two species were roughly similar. Lowest con centrations were found in the oxidized zone, including both the oxic s urface layer and the suboxic zone of intense manganese and iron reduct ion, and concentrations tended to increase through the suboxic and int o the reduced, sulfidic zone. The similarity of SO32- and S2O32- profi les suggested a close coupling of the cycling of the two species. Rate s of consumption were suggested as the main factor governing their dis tribution. Rapid turnover times for S2O32- and H2S of 4 and 1. 1 h, re spectively, were estimated for the upper 0-1 cm of a subtidal sediment .