Competitive binding of protons and metal ions in humic substances by lanthanide ion probe spectroscopy

Dobbs, J. C.; Susetyo, W.; Carreira, L. A.; Azarraga, L. V.

doi:10.1021/ac00189a012

Cited by 55 publications

(26 citation statements)

References 16 publications

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“…Indeed, increasing the pH should, in the absence of a chelator, favor Fe(III) hydrolysis and precipitation, especially at pH 8 (34), and hence be deleterious to the cells. Modeling calculations suggest that as the pH increases, a greater proportion of Fe(II) is bound to humic substances, which can be explained if Fe(II) and protons compete for carboxylic binding sites on humic substances (13,39). However, over the range of pHs tested, protonation is not expected to significantly affect NTA speciation or its binding to Fe(II), which is consistent with our observation that the Fe(II) oxidation rate is indifferent to the pH when Fe(II)-NTA is the substrate.…”

Section: Discussionmentioning

confidence: 99%

Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism

Poulain

Newman

2009

Appl Environ Microbiol

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Diverse bacteria are known to oxidize millimolar concentrations of ferrous iron [Fe(II)] under anaerobic conditions, both phototrophically and chemotrophically. Yet whether they can do this under conditions that are relevant to natural systems is understood less well. In this study, we tested how light, Fe(II) speciation, pH, and salinity affected the rate of Fe(II) oxidation by Rhodobacter capsulatus SB1003. Although R. capsulatus cannot grow photoautotrophically on Fe(II), it oxidizes Fe(II) at rates comparable to those of bacteria that do grow photoautotrophically on Fe(II) as soon as it is exposed to light, provided it has a functional photosystem. Chelation of Fe(II) by diverse organic ligands promotes Fe(II) oxidation, and as the pH increases, so does the oxidation rate, except in the presence of nitrilotriacetate; nonchelated forms of Fe(II) are also more rapidly oxidized at higher pH. Salt concentrations typical of marine environments inhibit Fe(II) oxidation. When growing photoheterotrophically on humic substances, R. capsulatus is highly sensitive to low concentrations of Fe(II); it is inhibited in the presence of concentrations as low as 5 M. The product of Fe(II) oxidation, ferric iron, does not hamper growth under these conditions. When other parameters, such as pH or the presence of chelators, are adjusted to promote Fe(II) oxidation, the growth inhibition effect of Fe(II) is alleviated. Together, these results suggest that Fe(II) is toxic to R. capsulatus growing under strictly anaerobic conditions and that Fe(II) oxidation alleviates this toxicity.

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Section: Discussionmentioning

confidence: 99%

Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism

Poulain

Newman

2009

Appl Environ Microbiol

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“…The most recent version of CHEAQS now incorporates WHAM V in its data base. Conversely, the program MINTEQA2 gives the user three options to model DOC; Gaussian [91], NICA-Donnan [79] and the Stockholm humic acid model [8,23].…”

Section: Discussionmentioning

confidence: 99%

Application of Chemical Speciation Modelling to Studies on Toxic Element Behaviour in Soils

Evans

Barabash

Lumsdon

et al. 2010

Trace Elements in Soils

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“…The traditionally unfriendly interface of this code has led to the development of at least two commercial versions, MINEQL+ (www.mineql.com) and MINTEQA2 for Windows (www.allisongeoscience.com), and a freely distributed version (www.lwr.kth.se/English/OurSoftware/vminteq/). MINTEQA2 incorporates a relatively unsophisticated way of modelling NOM binding: it includes a Gaussian distribution model based on the assumption that NOM is a complex mixture of various functional groups which comprise a population of binding sites and that the probability of occurrence of a binding site is normally distributed with respect to its log K value for metal or proton binding [10,11]. Both publications include data for humic substances.…”

Section: Speciation Modellingmentioning

confidence: 99%

Quantifying ‘humics’ in freshwaters: purpose and methods

Filella

2010

Chemistry and Ecology

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Natural organic matter (NOM) plays an important role in many environmentally relevant processes. NOM includes many different types of compounds, not all of which behave similarly. Much effort has gone into characterising some fractions of NOM (e.g. humic substances) in the different environmental compartments, in finding tracers to ascertain their origin, etc. However, few methods exist for quantifying the different types of NOM and, as a result, field studies have limited themselves to measuring only total or dissolved organic carbon. In this article, the few existing methods for humic substance quantification are reviewed, and the implications of the current lack of simple measurement methods are discussed in relation to two fields of high environmental relevance: trace element speciation modelling and natural colloid and engineered nanoparticle fate.

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Competitive binding of protons and metal ions in humic substances by lanthanide ion probe spectroscopy

Cited by 55 publications

References 16 publications

Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism

Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism

Application of Chemical Speciation Modelling to Studies on Toxic Element Behaviour in Soils

Quantifying ‘humics’ in freshwaters: purpose and methods

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