The possibilities of voltammetry in the study reactivity of dissolved organic carbon (DOC) in natural waters

Changes in organic carbon properties during intense plankton blooms and macroaggregate formation in the coastal Adriatic Sea, Croatia (case studies in 2020-2022)

“…SAS were analyzed with the electrochemical method of a.c. voltammetry (out-of-phase mode; Ciglenečki et al, 2023;Ćosović & Vojvodić, 1998). The method is based on the measurement of the adsorption effect of SAS on the surface of a hanging mercury drop electrode as a working electrode at a potential of -0.6 V (vs. Ag|AgCl, 3 M KCl; Ćosović & Vojvodić, 1998) at initial seawater (pH around 8).…”

“…Due to the adsorption of surface-active organic material, the decrease in the capacitive current below the value for pure electrolyte was recorded (see voltammograms in the Results and Discussion sections), which was then expressed as the equivalent adsorption effect (mg L -1 ) of the non-ionic model substance Triton-X-100 (octyl phenol ethylene oxide condensate; Supplementary Material Fig. S1A; Ciglenečki et al, 2023). Triton-X-100 has been shown to be a good representative of the majority of the reactive fraction of SAS in natural waters.…”

“…SAS were then normalized to DOC content to obtain the value of NSA = [SAS (eq. T-X-100)/DOC], the graphical representation of which provides a more accurate visual characterization of the nature of DOC (Ciglenečki et al, 2023;Ćosović et al, 2007). NSA can be compared with NSA of different model SAS (Table 1), which are representative of the surfactants present in the OM pool of natural samples (Ciglenečki et al, 2023;Ćosović & Vojvodić, 1998;Ćosović et al, 2000).…”

“…Surface-active substances (SAS) represent a crucial portion of DOC in marine ecosystems (Ciglenečki et al, 2020a;Ćosović et al, 2000;Simonović et al, 2023). Due to their different origins (allochthonous or autochthonous) and complex composition, the different types of DOC have significantly different physicochemical properties, including surface activity (Ciglenečki et al, 2023;Ćosović & Ciglenečki, 1997;Karavoltsos et al, 2015;Plavšić et al, 2007;Scoullos et al, 2006).…”

“…The normalization of SAS to DOC provides so-called DOC normalized surfactant activity (NSA = SAS/DOC) as a practical parameter for assessing and monitoring DOC reactivity-hydrophobicity in different water environments (Ciglenečki et al, 2023;Karavoltsos et al, 2015;Simonović et al, 2023 and references therein).…”