Electrochemical characterization of Cobalt(II)-Complexes involved in marine biogeochemical processes. I. Co(II)-4-nitrocatechol and Co(II)-Humate

Bačinić, Anđela; Tumir, Lidija-Marija; Mlakar, Marina

doi:10.1016/j.electacta.2020.135797

Cited by 5 publications

(4 citation statements)

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“…Cobalt forms strong complexes with organic ligands, and in some surface waters over 99% of dissolved Co may be complexed [100]. The statistically significant positive correlations among Co, DOC and SAS (Figures 4 and 5, Table 1), and N-POM (Supplementary Figure S4) at station 108 confirm Co affinity for DOM, probably with the freshly produced OM [101], as the same correlations were not statistically significant at station 107, characterized with lower primary production and therefore with less fresh OM. The statistically significant positive correlation between dissolved Co and PO 4 3− at station 107 suggests a nutrient-like behavior of Co. At station 108, the correlation between dissolved Co and PO 4 3− was also positive but not statistically significant.…”

Section: Dom Impacts On the Distribution Of Tms In The Northern Adriaticmentioning

confidence: 78%

Dissolved Trace Metals and Organic Matter Distribution in the Northern Adriatic, an Increasingly Oligotrophic Shallow Sea

Penezić

Gašparović

Cuculić

et al. 2022

Water

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We report a monthly distribution of Zn, Cd, Pb, Cu, Ni and Co, biologically relevant trace metals (TMs), within one year, in the productive surface layer at two stations with different trophic characters in the northern Adriatic (NA). The TM data was accompanied by a multivariable dataset, including dissolved organic carbon (DOC), surface-active organic substances (SAS), nitrogen-containing polymeric organic material (N-POM), nutrients, pH, dissolved O2, chlorophyll a (Chl a), seawater temperature, and the Po River discharge rate. At the eu- to mesotrophic station 108, the concentrations of dissolved TMs were 5–116 nM for Zn, 0.04–0.18 nM for Cd, 0.05–0.63 nM for Pb, 3–17 nM for Cu, 4–11 nM for Ni, and 0.2–1.2 nM for Co, while at the oligotrophic station 107, they were 6–224 nM for Zn, 0.03–0.16 nM for Cd, 0.05–1.25 nM for Pb, 3–17 nM for Cu, 4–19 nM for Ni, and 0.1–0.7 nM for Co. The characterization of organic matter (OM) in conjunction with the analysis of correlations with TMs indicated that the OM–TMs interactions differed between the two stations; namely, the freshly produced OM detected at station 108 was probably involved in the complexation of Cu, Co, Cd, and Ni, whereas at station 107, such complexation processes were not present. Accumulation of DOC was observed during the summer months at both stations. Our results present a significant contribution to biogeochemical studies in the NA by focusing on the complexity of TM–OM interactions, which is a prerequisite for interpretation of their responses to local and global changes.

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Section: Dom Impacts On the Distribution Of Tms In The Northern Adriaticmentioning

confidence: 78%

Dissolved Trace Metals and Organic Matter Distribution in the Northern Adriatic, an Increasingly Oligotrophic Shallow Sea

Penezić

Gašparović

Cuculić

et al. 2022

Water

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“…To investigate the identity of the dCo‐binding organic ligands in the East China Sea, we applied the reverse titration method for two model ligands: (1) terrestrial humic acid, and (2) cyanocobalamin. Previous studies have found that dCo can form organic complexes with humic acid (Yang and van den Berg 2009; Bacinic et al 2020), while cyanocobalamin is an essential micronutrient that contains Co (Rickes et al 1948; Brink et al 1950; Abeles and Dolphin 1976). Our results showed that both humic acid and cyanocobalamin in seawater are not the predominant dCo‐binding organic ligands in the East China Sea.…”

Section: Resultsmentioning

confidence: 99%

“…In the samples containing humic acid, the voltametric peak current reached a maximum at 1 μM Nx concentrations (α Nx = 1.3 × 10 6 ). Voltammetric analyses revealed that log K ′ Co‐(humic)2 was ~ 11.3 (Bacinic et al 2020). Yang and van den Berg (2009) also found a relatively low log K ′ Co‐humic of ~ 8.7 using forward titration CLE‐AdCSV.…”

Section: Resultsmentioning

confidence: 99%

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Very strong but exchangeable organic ligand of cobalt in the marginal sea

Wong

Kondo

et al. 2022

Limnology & Oceanography

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Cobalt (Co) is an important micronutrient for phytoplankton and its chemical speciation in the ocean is dominated by organic complexation. However, determination of the chemical speciation parameters of dissolved Co (dCo) in seawater is difficult because the ligands have conditional stability constants (K′) higher than those detectable by current forward titration methods. Furthermore, forward titration is not ideal when the ligand concentration is less than the dCo concentration in natural seawater, which is a probable scenario because excess ligands will bind more strongly to nickel instead. In this study, we successfully determined the concentrations and K′ of the dCo‐binding organic ligands in East China Sea using the reverse titration method. Our results indicate that organic complexes of dCo in the East China Sea are very strong but are kinetically exchangeable at high detection windows. Log K′ values of the ligands were between 16.6 and 17.1 in the Kuroshio waters and ranged from 19.7 to 20.9 in coastal waters. These ligands might be phytoplankton exudates or degradation products of cobalamin. Our findings suggest that an inert dCo fraction may be significant in coastal regions with high primary productivity. These inert dCo complexes were not detected within our detection window, which may lead to overestimation of the titration results.

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