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Sulfur species in Rogoznica Lake - extreme anoxic seawater system on the Adriatic Coast

By using different electrochemical methods it is possible to measure a variety of soluble and particulate sulfur compounds in natural waters. In this work we used hanging mercury drop electrode to measure different dissolved reduced sulfur species (RSS), including S(-II), S(0) and Sx(-II) species in anoxic seawater lake. In parallel, possibility of using UV/VIS spectrophotometry in determination of S(0), Sx(-II)) was tested. Concentration of total RSS in anoxic water column of Rogoznica Lake is relatively high, up to 2 x 10-3 M. Polysulfide concentrations are extremly high with detected numbers of 3.5 x 10-5 M implying that polysulfides are contributing the most to the total S(0) (up to the 1.7 x 10-4 M) measured by voltammetry. High concentrations of total S(0) in Rogoznica Lake are most probably consequence of bacterial oxidation of S(-II) proved by presence of phototrophic sulfur bacteria, Chromatium sp. Polarographic measurements with the use of dropping Hg electrode together with spectrophotometric measurements are found as useful techniques for determination of polysulphide species in Rogoznica Lake.

sulphur species; electrochemistry; spectrophotometry; anoxic conditions; Rogoznica Lake

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