Opredelenie vosstanovlennykh form sery v vode anaerobnykh basseynov

Abstract

Introduction. Development of anoxia in marine basins leads to formation of hydrogen sulfide and the intermediate reduced sulfur species – thiosulfate, sulfite, zero-valent sulfur and sulfur of polysulfides. Except for thiosulfate, the data on the other reduced species of sulfur in the Black Sea water are scarce. The thiosulfate concentration in the papers of different authors varies from 20 to 40 μM; and it can be a consequence of hydrogen sulfide oxidation during sampling and analyzing. Data and methods. The previously proposed (by I. I. Volkov and N. N. Zhabina) method for determining the sulfur reduced species (sulfite + thiosulfate, zero-valent sulfur + sulfur of polysulfides) in the anaerobic basins’ water has been re-evaluated and developed. Addition of suspension Zn 2 (OH) 2 CO 3 to a seawater sample destructs polysulfides and converts the elemental sulfur into precipitation. The elemental sulfur, sulfur polysulfides and sulfides are separated from the sum of thiosulfate and sulfite by filtration. To analyze the reduced species of sulfur, we applied their reduction to hydrogen sulfide which is determined spectrophotometrically after its distillation in the argon stream and precipitation as ZnS. Results. The results of determining the sulfur species were tested by analyzing 2% solutions of NaCl with the introduced contents of thiosulfate (0.5–1.5 μmol), sulfite (< 1 μmol), elemental sulfur (< 1 μmol) against the background of much higher concentrations of hydrogen sulfide (60 µmol). Such ratios of concentrations of the sulfur and hydrogen sulfide reduced species are found in the Black Sea water. Discussion and conclusion. It is shown that the proposed method correctly reflects presence of the reduced species of sulfur in the solutions. To analyze the sulfur species, the Niskin bottles are necessarily filled with the inert gas and the samples are filtered in the inert atmosphere. The method for determining the sulfur reduced species is highly sensitive. The detection limit for (S 2 O 3 2- +- SO 3 2- ) is 0.03 μM, for (S 0 + S 0 polysulfide) is 0.02 μM and for sulfide sulfur – 0.01 μM.