β-O-4 type dilignol compounds and their iron complexes for modeling of iron binding to humic acids: synthesis, characterization, electrochemical studies and algal growth experiments

Orlowska, Ewelina; Enyedy, Éva A.; Pignitter, Marc; Jirsa, Franz; Krachler, Regina; Kandioller, Wolfgang; Keppler, Bernhard K.

doi:10.1039/c7nj02328f

Cited by 5 publications

(5 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sato et al (2019) have shown that, in peatland-draining rivers, there is a strong positive correlation between the concentrations of CDOM and dissolved iron (dFe) whereby only the SAHLs-bound fraction of river iron is soluble in seawater, that is, it withstands coagulation and subsequent flocculation. Riverine SAHLs originate mainly from organic soil horizons with very wet conditions, such as raised bogs, swamps, forested peatlands, and other types of wetlands common in the catchment areas of CDOM-rich rivers and streams. − …”

Section: Steep Upward Trends Of Chlorophyll Concentrations In Surface...mentioning

confidence: 99%

“…In other types of soils, dissolved phenolic compounds are much less abundant. This is noteworthy because phenolic compounds (originating from the leaves of Sphagnum moss and/or from lignin degradation) play a key role as building blocks of Fe-binding humic substances in peatland runoff. , Krachler et al (2012) extracted Fe-binding SAHLs from a peatland-draining creek. These iron complexes (that were easily soluble in seawater) were further investigated using asymmetric flow field-flow-fractionation.…”

Section: Structural Information On Iron-binding Small Aquatic Humic L...mentioning

confidence: 99%

See 1 more Smart Citation

Northern High-Latitude Organic Soils As a Vital Source of River-Borne Dissolved Iron to the Ocean

Krachler

2021

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

Organic soils in the Arctic−boreal region produce small aquatic humic ligands (SAHLs), a category of naturally occurring complexing agents for iron. Every year, large amounts of SAHLsloaded with iron mobilized in river basinsreach the oceans via river runoff. Recent studies have shown that a fraction of SAHLs belong to the group of strong iron-binding ligands in the ocean. That means, their Fe(III) complexes withstand dissociation even under the conditions of extremely high dilution in the open ocean. Fe(III)-loaded SAHLs are prone to UV-photoinduced ligand-to-metal charge-transfer which leads to disintegration of the complex and, as a consequence, to enhanced concentrations of bioavailable dissolved Fe(II) in sunlit upper water layers. On the other hand, in water depths below the penetration depth of UV, the Fe(III)-loaded SAHLs are fairly resistant to degradation which makes them ideally suited as long-lived molecular transport vehicles for river-derived iron in ocean currents. At locations where SAHLs are present in excess, they can bind to iron originating from various sources. For example, SAHLs were proposed to contribute substantially to the stabilization of hydrothermal iron in deep North Atlantic waters. Recent discoveries have shown that SAHLs, supplied by the Arctic Great Rivers, greatly improve dissolved iron concentrations in the Arctic Ocean and the North Atlantic Ocean. In these regions, SAHLs play a critical role in relieving iron limitation of phytoplankton, thereby supporting the oceanic sink for anthropogenic CO 2 . The present Critical Review describes the most recent findings and highlights future research directions.

show abstract

Section: Steep Upward Trends Of Chlorophyll Concentrations In Surface...mentioning

confidence: 99%

Section: Structural Information On Iron-binding Small Aquatic Humic L...mentioning

confidence: 99%

Northern High-Latitude Organic Soils As a Vital Source of River-Borne Dissolved Iron to the Ocean

Krachler

2021

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Theoretical approaches to the classification of metals and ligands in solution tell us that Fe 3+ is a hard Lewis acid which will tend to form strong complexes with correspondingly hard ligands such as OH − (Morel and Hering, 1993;Stumm and Morgan, 1996;Luther, 2016). Recent XAS analyses of terrigenous humic substances have indeed shown that iron complexation was only dependent on oxygen containing groups such as carbonyl and phenol (Blazevic et al, 2016;Orlowska et al, 2017a). This, in turn, is consistent with the view that lignin products are important in maintaining iron in solution (Murphy et al, 2008;Krachler et al, 2012) and also that functional groups residing in the proximity of aromatic structures within the humics are especially significant (Fujii et al, 2014).…”

Section: What Do We Know About the Nature And Structure Of Iron-bindimentioning

confidence: 99%

“…It is also worth comparing the above iron-humic complexation studies with studies of iron binding at the iron oxide-DOM interface, such as occurs in sediments where iron and organic carbon mutually stabilize each other. Such a comparison reveals that the same functional groups (carboxylic, phenolic, catechol) are involved in the stabilization of iron in solution (Blazevic et al, 2016;Orlowska et al, 2017a) as in the stabilization of nanoscale iron and manganese oxides in sediments (Lalonde et al, 2012;Johnson et al, 2015), or indeed in the stabilization of engineered nanomaterials (Chen et al, 2015). Therefore, determining the control that humic ligands exert on the iron cycle would benefit from extensive transfer of information and collaboration opportunities between the seawater chemistry and sedimentary organic geochemistry communities.…”

Section: What Do We Know About the Nature And Structure Of Iron-bindimentioning

confidence: 99%

Exploring the Potential Role of Terrestrially Derived Humic Substances in the Marine Biogeochemistry of Iron

Muller

2018

Front. Earth Sci.

View full text Add to dashboard Cite

There is a widely recognized link between iron bioavailability and phytoplankton growth in large tracts of the World Ocean. Iron bioavailability is thus pivotal to the removal of atmospheric carbon via the ocean's 'biological pump.' To evaluate future scenarios of global climate change, we must therefore understand better how the bioavailability of iron in seawater is linked to processes controlling its supply, chemical speciation and removal from the water column. Much of the research on iron inputs to the open ocean has focused on atmospheric, benthic (shelf sediments) and hydrothermal (midocean) sources of iron. The conventional wisdom has been that riverine iron sources are negligible because many of the major world rivers exhibit extensive removal of dissolved iron by flocculation processes during estuarine mixing. However, recent studies have revealed that a fraction of iron associated with peatland-derived humic and fulvic acids may survive aggregation processes in the freshwater-seawater mixing zone, and thus be exported offshore. This review is a synthesis of available data and information for and against the hypothesis that land-derived humic substances exert a significant control on the marine biogeochemical cycle of iron. From the outset, it is shown that this hypothesis can neither be verified nor disproved at present, in part due to analytical difficulties in characterizing the all-important marine colloidal phase. Evidence is then presented on the likely chemical nature and structure of iron-binding humic ligands along with implications for the lateral transport of iron in surface waters and its participation in carbon stabilization in marine sediments. This is followed by a discussion of photochemically and microbially mediated processes acting on terrestrial humic substances and a discussion of how terrestrial humic substances may influence the biological availability of iron. The review finishes with a presentation of measurement technologies and approaches that could be used to assess (i) how iron-binding ligands in seawater relate to land-derived humic substances and (ii) how terrestrial humics may influence the global carbon cycle indirectly by influencing the processes that control the supply and maintain the pool of 'dissolved' iron in the ocean.

show abstract

“…Among all possible organic compounds, polyphenols are relevant because they form complexes with Fe, by forming strong or weak bonds, modifying its chemical speciation and bioavailability (Brown et al, 1998;Witter et al, 2000;Lodovici et al, 2001;Mira et al, 2002;Sroka and Cisowski, 2003;Andjelković et al, 2006;Santana-Casiano et al, 2010, 2014González et al, 2019;Arreguin et al, 2021). Polyphenols can reach the ocean via terrestrial supply and can be considered as model ligands within the group of humic substances (Krachler et al, 2005(Krachler et al, , 2010(Krachler et al, , 2012(Krachler et al, , 2015(Krachler et al, , 2016(Krachler et al, , 2019Blazevic et al, 2016;Orlowska et al, 2016Orlowska et al, , 2017aRathgeb et al, 2017). In the ocean, they are excreted by marine diatoms and green algae, particularly under metallic stress conditions (Rico et al, 2013;López et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Ocean Acidification Effect on the Iron-Gallic Acid Redox Interaction in Seawater

et al. 2022

View full text Add to dashboard Cite

Ocean acidification impacts the iron (Fe) biogeochemistry both by its redox and its complexation reactions. This has a direct effect on the ecosystems due to Fe being an essential micronutrient. Polyphenols exudated by marine microorganisms can complex Fe(III), modifying the Fe(II) oxidation rates as well as promoting the reduction of Fe(III) to Fe(II) in seawater. The effect of the polyphenol gallic acid (GA; 3,4,5-trihydroxy benzoic acid) on the oxidation and reduction of Fe was studied. The Fe(II) oxidation rate constant decreased, increasing the permanence of Fe(II) in solutions at nM levels. At pH = 8.0 and in the absence of gallic acid, 69.3% of the initial Fe(II) was oxidized after 10 min. With 100 nM of gallic acid (ratio 4:1 GA:Fe), and after 30 min, 37.5% of the initial Fe(II) was oxidized. Fe(III) is reduced to Fe(II) by gallic acid in a process that depends on the pH and composition of solution, being faster as pH decreases. At pH > 7.00, the Fe(III) reduction rate constant in seawater was lower than in NaCl solutions, being the difference at pH 8.0 of 1.577 × 10–5 s–1. Moreover, the change of the Fe(III) rate constant with pH, within the studied range, was higher in seawater (slope = 0.91) than in NaCl solutions (slope = 0.46). The Fe(III) reduction rate constant increased with increasing ligand concentration, being the effect higher at pH 7.0 [k′ = 1.078 × 10–4 s–1; (GA) = 250 nM] compared with that at pH 8.0 [k′ = 3.407 × 10–5 s–1; (GA) = 250 nM]. Accordingly, gallic acid reduces Fe(III) to Fe(II) in seawater, making possible the presence of Fe(II) for longer periods and favoring its bioavailability.

show abstract

β-O-4 type dilignol compounds and their iron complexes for modeling of iron binding to humic acids: synthesis, characterization, electrochemical studies and algal growth experiments

Abstract: A series of β-O-4 type dilignols and their iron(iii) complexes were evaluated as model compounds for humic acids.

Cited by 5 publications

References 60 publications

Northern High-Latitude Organic Soils As a Vital Source of River-Borne Dissolved Iron to the Ocean

Northern High-Latitude Organic Soils As a Vital Source of River-Borne Dissolved Iron to the Ocean

Exploring the Potential Role of Terrestrially Derived Humic Substances in the Marine Biogeochemistry of Iron

Ocean Acidification Effect on the Iron-Gallic Acid Redox Interaction in Seawater

Contact Info

Product

Resources

About