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

Zmajevo oko – a unique example of anchialine system on the Adriatic coast (Croatia) during spring-summer stratification and autumn mixing period

Zmajevo oko is a naturally eutrophicated saline lake situated on the Gradina Peninsula, close to the village of Rogoznica on the central Dalmatian coast. Since 1992 the Lake has been intensively studied and in 2011 hydrographic and water column stratification in relation with reduced sulfur species and microbial activity was investigated during two different seasons: the spring-summer stratification and autumn mixing period

Voltammetric Study of Organic Matter Components in the Upper Reach of the Krka River, Croatia

The increased amount of organic matter (OM) accompanied with the development of hypoxia/anoxia and appearance of the sulphur species are indicators of eutrophication in natural waters. To predict biogeochemical and ecological changes, specific OM components in the Lake Brljan (the karst Krka River, Croatia; station B and station B2 downstream) were studied during 2011 and in January 2012 using voltam¬metry. Surface‒active substances (eq. 0.018 to 0.150 mg dm–3 Triton‒X‒100) and Cu complexing capacity (54‒680 nmol dm–3) showed the highest values in surface water layer in May 2011 (B) and in November 2011 (B2), associated with the highest dissolved (0.505‒1.530 mg C dm–3) and particulate (0.051‒0.725 mg C dm–3) organic carbon and phytoplankton biomass. Autochthonously produced OM did not cause hypoxia/anoxia during the investigated period. Brljan\u27s lake water could be characterised as oligotrophic with occasionally elevated OM concentration depending on season and Krka River water regime. This work is licensed under a Creative Commons Attribution 4.0 International License

Diatoms in the extreme euxinic environment (Rogoznica Lake, eastern Adriatic coast)

Marine lake system, Rogoznica Lake is a small, karstic, naturally eutrophic and euxinic marine environment. Abundance and temporal distribution of phytoplankton was investigated in relation to environmental conditions in the period from 1998. - 2013. The 36 determined diatoms contributed to 90% to the total phytoplankton abundance. The diatom composition is characterized by low species diversity and high single species abundance (up to 107 cells L-1). There were, in average, 2.6 diatom species per sample (maximum 14 diatom species per sample) reflecting extreme environmental conditions. Dominant diatoms Thalassionema nitzschioides, Cyclotella choctawhatcheeana, Dactyliosolen fragilissimus and Chaetoceros curvisetus repeatedly occurred alternating in domination in the lake during the whole research period. Some diatoms were dominant only in limited period like Cyclotella choctawhatcheeana (evident since 2001), and Pseudo-nitzschia spp. (evident in the period 2002 to 2009). It appears that interplay of environmental conditions such as variability in thermohaline and redox conditions, nutrient and reduced sulphur concentration influence the phytoplankton development and abundance in the lake