Electroanalytical methods in characterization of sulfur species in aqueous environment

Electroanalytical (voltammetric, polarographic, chronoamperometric) methods on an Hg electrode were applied for studying of different sulfur compounds in model and natural water systems (anoxic lakes, waste water, rain precipitation, sea-aerosols). In all investigated samples typical HgS reduction voltammetric peak, characteristic for many different reduced sulfur species (RSS: sulfide, elemental sulfur, polysulfide, labile metal sulfide and organosulfur species) was recorded at about 0.6 V vs. Ag/AgCl reference electrode. In addition, in anoxic waters which are enriched with sulfide and iron species, voltammetric peaks characteristic for the presence of free Fe(II) and FeS nanoparticles (NPs) were recorded at -1.4 V and around -0.45 V, respectively. Depending on the used electroanalytical method and experimental conditions (varying deposition potential, varying time of oxidative and/or reductive accumulation, sample pretreatment i.e. acidification followed by purging) it is possible to distinguish between different sulfur species. This work clearly shows a large potential of the electrochemistry as a powerful analytical technique for screening water quality regarding presence of different reduced sulfur species and their speciation between dissolved and colloidal/nanoparticle phases.