Development of an electrochemical method for monitoring polysulfides (Sx2-) in marine euxinic environment

Mateša Đureković, Sarah (2024) Development of an electrochemical method for monitoring polysulfides (Sx2-) in marine euxinic environment. Doctoral thesis, Sveučilište u Zagrebu, Prirodoslovno-matematički fakultet.

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Abstract

The direct analytical determination of polysulfide (Sx2-) in seawater solutions is a challenge due to the low thermodynamic stability constants of Sx2-. To develop and apply a direct method for determining and characterizing Sx2-, its electrochemical behavior was investigated at a mercury (Hg) electrode. The marine euxinic environment of Lake Rogoznica – Zmajevo oko (RL) was chosen as a model for testing the electroanalytical method (EM), differential pulse voltammetry (DPV) for the direct determination of polysulfides under natural conditions. In addition to DPV, cyclic voltammetry (CV) and sampled DC voltammetry/polarography (SDC) were also used to monitor reduced sulfur species (RSS), i.e. Sx2-, as well as other analytical methods: UV/Vis spectrophotometry for additional determination of Sx2- and atomic force microscopy (AFM) and dynamic light scattering (DLS) to monitor changes in RSS properties. The change in cell morphology of phototrophic sulfur bacteria as a source of elemental S under different environmental and experimental conditions was monitored by AFM, while DLS monitored the change in hydrodynamic properties of elemental S under different dilution conditions. The DPV method was used to determine Sx2- in model solutions and the RL water column, with the highest concentrations measured in samples below the chemocline. The observation of the seasonal dynamics of Sx2- showed that its presence and concentration depend on physico-chemical and microbiological factors. The highest concentrations, up to 89 μM polysulfide S0, were determined in summer during pronounced stratification of the water column and intense microbial activity when purple sulfur bacteria (PSB) predominate, while Sx2- was not detected during periods of weak stratification and occurrence of holomixia.

Item Type:

Thesis (Doctoral thesis)

Uncontrolled Keywords:

electroanalytical methods; differential pulse voltammetry; polysulfides; reduced sulfur species; euxinia; Rogoznica Lake – Dragons eye

Subjects:

NATURAL SCIENCES > Interdisciplinary Natural Sciences
NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science

Divisions:

Division for Marine and Enviromental Research

Projects: