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  • 1
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    Hydroxamate siderophores: Occurrence and importance in the Atlantic Ocean (2008)
    American Chemistry Society
    In:  Environmental Science and Technology, 42 (23). pp. 8675-8680.
    Details
    Publication Date: 2017-10-24
    Description: Siderophores are chelates produced by bacteria as part of a highly specific iron uptake mechanism. They are thought to be important in the bacterial acquisition of iron in seawater and to influence iron biogeochemistry in the ocean. We have identified and quantified two types of siderophores in seawater samples collected from the Atlantic Ocean. These siderophores were identified as hydroxamate siderophores, both ferrioxamine species representative of the more soluble marine siderophores characterized to date. Ferrioxamine G was widely distributed in surface waters throughout the Atlantic Ocean, while ferrioxamine E had a more varied distribution. Total concentrations of the two siderophores were between 3 and 20 pM in the euphotic zone. If these compounds are fully complexed in seawater, they represent approximately 0.2-4.6 of the 〈0.2 μm iron pool. Our data confirm that siderophore-mediated iron acquisition is important for marine heterotrophic bacteria and indicate that siderophores play an important role in the oceanic biogeochemical cycling of iron. © 2008 American Chemical Society.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1021/es801884r
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Chemical speciation of dissolved Cu, Ni, and Co in a contaminated estuary in southwest Spain and its influence on plankton communities (2007)
    American Chemistry Society
    In:  Environmental Science and Technology, 41 (12). pp. 4214-4220.
    Details
    Publication Date: 2017-10-24
    Description: Four surveys of the Huelva Estuary in southwest Spain and its sources, the Tinto and the Odiel Rivers, were carried out between 1996 and 1998. The surveys investigated the impact of metalliferous mining of sulfide-rich ores in the catchment area on metal speciation, metal concentrations in a macrophyte, and phytoplankton diversity and abundance. Chemical speciation measurements in the lower Tinto Estuary showed that metals were predominantly electrochemically labile (>99 of total dissolved Cu, Co, and Ni at 10 μM Cu, 424 nM Co, and 500 nM Ni, S = 28). Concentrations of Cu complexing ligands and free cupric ions Cu2+ in the Gulf of Cádiz ranged between 5.3 and 38 nM and 0.2-7.9 pM, respectively, with conditional stability constants of the ligands of log K′CuL = 11.7-12.6. At enhanced dissolved Cu concentrations in the lower Huelva Estuary, Cu complexing ligands were saturated with Cu, resulting in nanomolar Cu2+, which increased upstream. Metal tissue concentrations of the macrophyte Blindingia marginata were high, and a clear relationship between dissolved labile Cu and macrophyte tissue Cu concentrations was observed. A low biodiversity was observed in the Huelva system (Shannon-Wiener indices (H) typically 〈0.2). Nevertheless, the maximum biomass was observed in the lower Tinto Estuary, which showed high labile metal and nutrient concentrations and a low biodiversity (H 〈 0.02), thereby suggesting adaptation through evolutionary processes of the phytoplankton community to the harsh conditions. © 2007 American Chemical Society.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1021/es063042h
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    In situ measurements of explosive compound dissolution fluxes from exposed munition material in the Baltic Sea (2019)
    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 53 (10). pp. 5652-5660.
    Details
    Publication Date: 2022-01-31
    Description: Underwater munitions containing millions of tons of toxic explosives are present worldwide in coastal marine waters as a result of unexploded ordnance and intentional dumping. Dissolution flux of solid explosives following corrosion of metal munition housings controls exposure of biological receptors to toxic munition compounds (MC; including TNT: 2,4,6-Trinitrotoluene, RDX: 1,3,5-Trinitro-1,3,5-triazinane, and DNB: 1,3-Dinitrobenzene). Very little is known about the dissolution behavior of MC in the marine environment. In this work, we exploit a unique marine study site in the Baltic Sea with exposed solid explosives to quantify in situ MC dissolution fluxes using dissolved MC gradients near the exposed explosive surface, as well as benthic chamber incubations. The gradient method gave dissolution fluxes that ranged between 0.001 and 3.2, 0.0001 and 0.04, and 0.003 and 1.7 mg cm-2 d-1 for TNT, RDX, and DNB, respectively. Benthic chamber incubations indicated dissolution fluxes of 0.0047-0.277, 0-0.11, and 0.00047-1.45 mg cm-2 d-1 for TNT, RDX, and DNB, respectively. In situ dissolution fluxes estimated in the current study were lower than most dissolution rates reported for laboratory experiments, but clearly demonstrated that MC are released from underwater munitions to the water column in the Baltic Sea.
    Type: Article , PeerReviewed
    Format: text
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    DOI: 10.1021/acs.est.8b06974
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Seasonal Variations in Proton Binding Characteristics of Dissolved Organic Matter Isolated from the Southwest Baltic Sea (2021)
    ACS (American Chemical Society)
    Details
    Publication Date: 2024-02-07
    Description: The physicochemical characteristics of dissolved organic matter (DOM) strongly influence its interactions with inorganic species such as protons and trace elements in natural waters. We collected water samples at Boknis Eck, a time series station in the Baltic Sea with a low exposure to freshwater inputs, to investigate how seasonal fluctuations impact the proton binding properties of the isolated DOM. We used potentiometric titrations to assess the binding properties of solid-phase extracted DOM (SPE–DOM) over a seasonal cycle. We report and critically analyze the first NICA parameters estimates of carboxylic-like and phenolic-like sites for brackish water SPE–DOM. The total amount of functional groups (QmaxH,tot) showed no seasonal fluctuations and an average value of 136 ± 5.2 mmol·mol C–1. The average proton affinity (logKH) and binding site heterogeneity (m) showed a relatively minor variability for samples obtained between April and September, when the water remained stratified. These results contribute to a better understanding of the ion binding characteristics of DOM in natural brackish waters.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: archive
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Influence of pH and Dissolved Organic Matter on Iron Speciation and Apparent Iron Solubility in the Peruvian Shelf and Slope Region (2021)
    ACS (American Chemical Society)
    Details
    Publication Date: 2024-02-07
    Description: The chemical speciation of iron (Fe) in oceans is influenced by ambient pH, dissolved oxygen, and the concentrations and strengths of the binding sites of dissolved organic matter (DOM). Here, we derived new nonideal competitive adsorption (NICA) constants for Fe(III) binding to marine DOM via pH-Fe titrations. We used the constants to calculate Fe(III) speciation and derive the apparent Fe(III) solubility (SFe(III)app) in the ambient water column across the Peruvian shelf and slope region. We define SFe(III)app as the sum of aqueous inorganic Fe(III) species and Fe(III) bound to DOM at a free Fe (Fe3+) concentration equal to the limiting solubility of Fe hydroxide (Fe(OH)3(s)). A ca. twofold increase in SFe(III)app in the oxygen minimum zone (OMZ) compared to surface waters is predicted. The increase results from a one order of magnitude decrease in H+ concentration which impacts both Fe(III) hydroxide solubility and organic complexation. A correlation matrix suggests that changes in pH have a larger impact on SFe(III)app and Fe(III) speciation than DOM in this region. Using Fe(II) measurements, we calculated ambient DFe(III) and compared the value with the predicted SFe(III)app. The underlying distribution of ambient DFe(III) largely reflected the predicted SFe(III)app, indicating that decreased pH as a result of OMZ intensification and ocean acidification may increase SFe(III)app with potential impacts on surface DFe inventories.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Proton Binding Characteristics of Dissolved Organic Matter Extracted from the North Atlantic (2023)
    ACS (American Chemical Society)
    Details
    Publication Date: 2024-02-07
    Description: Marine dissolved organic matter (DOM) presents key thermodynamic properties that are not yet fully constrained. Here, we report the distribution of binding sites occupied by protons (i.e., proton affinity spectra) and parametrize the median intrinsic proton binding affinities (log K̅H) and heterogeneities (m), for DOM samples extracted from the North Atlantic. We estimate that 11.4 ± 0.6% of C atoms in the extracted marine DOM have a functional group with a binding site for ionic species. The log K̅H of the most acidic groups was larger (4.01–4.02 ± 0.02) than that observed in DOM from coastal waters (3.82 ± 0.02), while the chemical binding heterogeneity parameter increased with depth to values (m1= 0.666 ± 0.009) ca. 10% higher than those observed in surface open ocean or coastal samples. On the contrary, the log K̅H for the less acidic groups shows a difference between the surface (10.01 ± 0.08) and deep (9.22 ± 0.35) samples. The latter chemical groups were more heterogeneous for marine than for terrestrial DOM, and m2 decreased with depth to values of 0.28 ± 0.03. Binding heterogeneity reflects aromatic carbon compounds’ persistence and accumulation in diverse, low-abundance chemical forms, while easily degradable low-affinity groups accumulate more uniformly in the deep ocean.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Rapid, At-Sea Detection of Munition Compounds in Coastal Waters Using a Shipboard System (2023)
    ACS (American Chemical Society)
    Details
    Publication Date: 2024-02-29
    Description: Coastal waters are contaminated globally with millions of metric tons of munitions from the two world wars which constitute a potential threat to ecosystems and humans. Laboratory-based chemical methods for the detection of munition compounds (MCs) in seawater typically take weeks to months between sample collection and analysis. The current work details a novel, field-deployable system for rapid (under 10 min) analysis of four common MCs (1,3-dinitrobenzene (DNB), amino-4,6-dinitrotoluene (ADNT), 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)). The system uses a fluidic preconcentration unit with high-performance liquid chromatography (HPLC) and detection by electrospray-ionization mass spectrometry and UV–vis spectroscopy. The fluidic unit comprises two solid-phase extraction (SPE) columns for preconcentration of target MCs from the seawater matrix and allows loading and analysis of two samples simultaneously. Seven SPE resins were tested for extraction efficiency and robustness, with Porapak RDX showing best performance. Chromatographic separation of target MCs was performed using a C8 reversed-phase HPLC column. Limits of detection (LODs) were 3.7, 1.8, 3.6, and 10.7 ng L–1 for DNB, ADNT, TNT, and RDX, respectively. The system’s analytical performance and automated data processing procedure were demonstrated in the Baltic Sea.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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