ASFit - An all-inclusive tool for analysis of UV–Vis spectra of colored dissolved organic matter (CDOM)

Omanović, Dario; Santinelli, Chiara; Marcinek, Saša; Gonnelli, Margherita

doi:10.1016/j.cageo.2019.104334

Cited by 15 publications

(10 citation statements)

References 66 publications

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“…The spectrum of Milli-Q water, measured in the same conditions, was used as blank and subtracted from each sample. UV-Vis spectra were treated using newly purpose-developed software package, ASFit (Omanović et al, 2019). In order to minimize light scattering interferences, baseline subtraction of average absorption between 650 and 700 nm was performed.…”

Section: Absorbance Measurementsmentioning

confidence: 99%

“…Average SSCs of freshwater (n = 9) and seawater samples (n = 6) as well as SSC for few typical samples was obtained by calculating the spectral slopes for 20 nm intervals across 200-500 nm wavelength range. ASFit procedure is described in detail in (Omanović et al, 2019). International Humic Substances Society) and tryptophan from Sigma-Aldrich; (ii) similar components reported in the literature and (iii) matching spectra obtained from the OpenFluor database (Murphy et al, 2014) (Table S1).…”

Section: Absorbance Measurementsmentioning

confidence: 99%

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Dissolved organic matter dynamics in the pristine Krka River estuary (Croatia)

et al. 2020

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In many estuarine systems, riverine discharge is the main source of dissolved organic matter (DOM). In contrast, karstic Krka River, with self-purifying ability, is characterized by very low DOM concentrations (~30 µM) and a diluting effect on DOM in the estuary. Interestingly, within the estuary a marked in-situ production is observed, particularly in summer. Pristine nature of the estuary makes it a natural laboratory to study the DOM dynamics, originated from 3 sources: the river the seawater and in-situ production. With this work we aim at reporting the first information on DOM dynamics in the Krka estuary in two contrasting seasons, winter and summer 2019. The quality of DOM was assessed using absorbance and fluorescence measurements coupled with PARAFAC analysis. During winter, the estuary is characterized by extremely low DOC concentrations, for which optical properties indicate that is mainly of terrestrial origin. In summer, due to the low riverine discharge and high temperature, DOC concentrations are higher than in winter and a marked increase in absorption and protein-like fluorescence is observed in the estuary. The permanent stratification determines DOC accumulation in the surface layer with values up to 147 µM, suggesting a decoupling between production and removal processes. Our work opens intriguing questions about the main processes responsible for DOC accumulation in this system and highlights the need of new studies combing chemical and biological information.

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Section: Absorbance Measurementsmentioning

confidence: 99%

Section: Absorbance Measurementsmentioning

confidence: 99%

Dissolved organic matter dynamics in the pristine Krka River estuary (Croatia)

et al. 2020

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“…In order to examine the continuous DOM size distribution in more detail, we applied a decomposition method that aims to utilize all the potential information contained in the size‐exclusion chromatograms. Decomposing analyte chromatograms is an established technique (Maeder 1987), but only recently it has been applied to natural CDOM absorbance spectra (Massicotte and Markager 2016; Omanović et al 2019). By using these spectral decomposition techniques with size‐exclusion spectra, we were able to separate distinct chromophore groups based on their size.…”

Section: Discussionmentioning

confidence: 99%

Identification of dissolved organic matter size components in freshwater and marine environments

Asmala

Massicotte

Carstensen

2021

Limnology & Oceanography

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Dissolved organic matter (DOM) in the transition zone from freshwater to marine systems was analyzed with a new approach for parameterizing the size distribution of organic compounds. We used size‐exclusion chromatography for molecular size analysis and quantified colored DOM (CDOM) on samples from two coastal environments in the Baltic Sea (Roskilde Fjord, Denmark and Gulf of Gdansk, Poland). We applied a Gaussian decomposition method to identify peaks from the chromatograms, providing information beyond bulk size properties. This approach complements methods where DOM is separated into size classes with pre‐defined filtering cutoffs, or methods where chromatograms are used only to infer average molecular weight. With this decomposition method, we extracted between three and five peaks from each chromatogram and clustered these into three size groups. To test the applicability of our method, we linked our decomposed peaks with salinity, a major environmental driver in the freshwater‐marine continuum. Our results show that when moving from freshwater to low‐salinity coastal waters, the observed steep decrease of apparent molecular weight is mostly due to loss of the high‐molecular‐weight fraction (HMW; >2 kDa) of CDOM. Furthermore, most of the CDOM absorbance in freshwater originates from HMW DOM, whereas the absorbing moieties are more equally distributed along the smaller size range (< 2 kDa) in marine samples.

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“…The spectrum of Milli-Q water, measured in the same conditions, was used as blank and subtracted from each sample. Absorbance spectra were treated by using the ASFit tool ( Omanović et al, 2019 ). Absorbance at 254 nm ( A 254 ) was expressed as the absorption coefficient ( a 254 ) in m −1 ( Stedmon and Nelson, 2015 ).…”

Section: Methodsmentioning

confidence: 99%

Organic Copper Speciation by Anodic Stripping Voltammetry in Estuarine Waters With High Dissolved Organic Matter

et al. 2021

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The determination of copper (Cu) speciation and its bioavailability in natural waters is an important issue due to its specific role as an essential micronutrient but also a toxic element at elevated concentrations. Here, we report an improved anodic stripping voltammetry (ASV) method for organic Cu speciation, intended to eliminate the important problem of surface-active substances (SAS) interference on the voltammetric signal, hindering measurements in samples with high organic matter concentration. The method relies on the addition of nonionic surfactant Triton-X-100 (T-X-100) at a concentration of 1 mg L−1. T-X-100 competitively inhibits the adsorption of SAS on the Hg electrode, consequently 1) diminishing SAS influence during the deposition step and 2) strongly improving the shape of the stripping Cu peak by eliminating the high background current due to the adsorbed SAS, making the extraction of Cu peak intensities much more convenient. Performed tests revealed that the addition of T-X-100, in the concentration used here, does not have any influence on the determination of Cu complexation parameters and thus is considered "interference-free." The method was tested using fulvic acid as a model of natural organic matter and applied for the determination of Cu speciation in samples collected in the Arno River estuary (Italy) (in spring and summer), characterized by a high dissolved organic carbon (DOC) concentration (up to 5.2 mgC L−1) and anthropogenic Cu input during the tourist season (up to 48 nM of total dissolved Cu). In all the samples, two classes of ligands (denoted as L1 and L2) were determined in concentrations ranging from 3.5 ± 2.9 to 63 ± 4 nM eq Cu for L1 and 17 ± 4 to 104 ± 7 nM eq Cu for L2, with stability constants logKCu,1 = 9.6 ± 0.2–10.8 ± 0.6 and logKCu,2 = 8.2 ± 0.3–9.0 ± 0.3. Different linear relationships between DOC and total ligand concentrations between the two seasons suggest a higher abundance of organic ligands in the DOM pool in spring, which is linked to a higher input of terrestrial humic substances into the estuary. This implies that terrestrial humic substances represent a significant pool of Cu-binding ligands in the Arno River estuary.

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ASFit - An all-inclusive tool for analysis of UV–Vis spectra of colored dissolved organic matter (CDOM)

Cited by 15 publications

References 66 publications

Dissolved organic matter dynamics in the pristine Krka River estuary (Croatia)

Dissolved organic matter dynamics in the pristine Krka River estuary (Croatia)

Identification of dissolved organic matter size components in freshwater and marine environments

Organic Copper Speciation by Anodic Stripping Voltammetry in Estuarine Waters With High Dissolved Organic Matter

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