Abstract
Thiosulfate is a sulfur compound in an intermediate oxidation state between sulfate and sulfide. It emerges during processes of sulfide oxidation in bacterial and chemical reactions. Thiosulfate plays a prominent role in oxidation of sulfide and its presence may clear the mechanism of redox reactions in the biogeochemical cycles of sulfur and carbon. This work presents the distribution of thiosulfate, determined by derivatization technique with reagent 2,2'-Dithiobis(5-nitropyridine), in the upper part of the Black Sea anoxic water column in 2018–2021. Observations were carried out annually at the station located seaward of Gelendzhik in the area of continental slope. Independently of observation time the concentration of thiosulfate rises depth wards simultaneously with increase of sulfide. The thiosulfate concentration above limit of detection 0.01 µM are found at water depth with density (σθ) of 16.3 kg/m3 and sulfide concentration of 8–11 µM. Thiosulfate reaches its maximum values of 0.30 µM at maximal studied depth of 600 m. We suggest that in the absence of oxidants in the anoxic waters the thiosulfate appearance is attributed to the process of sulfate reduction in reductive part of sulfur cycle. The thiosulfate disappears in the upper part of anoxic water column before the sulfide.
Published Version
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