Permeability Changes in Model and Phytoplankton Membranes in the Presence of Aquatic Humic Substances

Vigneault, Bernard; Percot, Aline; Lafleur, Michel; Campbell, Peter G. C.

doi:10.1021/es001087r

Cited by 198 publications

(185 citation statements)

References 21 publications

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“…Hence, the adsorbed humic substances might affect the properties of the algal surface by enhancing membrane permeability of both lipophilic metal complexes (24) and hydrophilic substances (25), by increasing the negative surface charge (6,11), and by adding the additional binding sites (10,11,26).…”

Section: Resultsmentioning

confidence: 99%

Effect of Humic Acid on Cd(II), Cu(II), and Pb(II) Uptake by Freshwater Algae: Kinetic and Cell Wall Speciation Considerations

Lamelas

Pinheiro

Slaveykova

2009

Environ. Sci. Technol.

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The present study examines the effect of humic acid on the uptake kinetics of Cd(II), Cu(II), and Pb(II) by the freshwater alga Chlorella kesslerii. The results demonstrated that the relative proportion of Pb in the cell wall layer is greater than that of the internalized Pb, while internalized Cd and Cu were comparable or greater than the adsorbed metal concentration. In the presence of 10 mg L -1 humic acid (HA), Cd and Cu uptake kinetics were consistent with that predicted by measured free metal concentrations. For Pb, the uptake flux and amount of lead bound to internalization and adsorption sites were an order of magnitude higher than those found at the same free lead ion concentrations in the presence of citric acid. Chemodynamic modeling suggested that the enhancement of the Pb uptake flux in the presence of HA originates from an increasing amount of Pb bound to the internalization sites through a ternary complex formation between lead-humic acid complex and internalization sites. Cell wall speciation calculations indicated that the lead-humic acid complex is the predominant species in the cell wall layer, while for Cu(II) and Cd(II) metal bound to the internalization (Cu) and adsorption (Cd) sites significantly dominated over the M-HA complex. The findings of the work show the relevance of the cell wall layer concentration and speciation and its key role in defining the local equilibrium conditions between metal and internalizations sites. The results of the present kinetic study have important consequences for improvement of the mechanistic understanding of the role of dissolved organic matter in metal uptake in phytoplankton and biogeochemical cycling of metals in the surface waters.

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Section: Resultsmentioning

confidence: 99%

Effect of Humic Acid on Cd(II), Cu(II), and Pb(II) Uptake by Freshwater Algae: Kinetic and Cell Wall Speciation Considerations

Lamelas

Pinheiro

Slaveykova

2009

Environ. Sci. Technol.

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“…It was suggested that, due to its surfactant-like properties, humic acid may intercalate among membrane phospholipids, resulting in a decrease in lipid-lipid interactions and an overall increase in membrane permeability (38). In such a case, an effect is likely to be observed for the SRHA, while no influence would be expected for the polysaccharides.…”

Section: Resultsmentioning

confidence: 99%

Influence of the Composition of Natural Organic Matter on Pb Bioavailability to Microalgae

Lamelas

Wilkinson

Slaveykova

2005

Environ. Sci. Technol.

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The current work examines the effects of model allochtonous (humic substances) and autochtonous (microbial polysaccharides) natural organic matter (NOM) on Pb speciation and bioaccumulation. The results demonstrated that polysaccharides, in particular alginic acid, had complexing properties and effects on Pb bioaccumulation by the green alga Chlorella kesslerii that were similar to equivalent complexing capacity of humic substances. Pb uptake decreased in the presence of humic, alginic, and polygalacturonic acids with respect to noncomplexed Pb, but accumulated Pb was higher than predicted from measured Pb 2+ concentrations or from previous results obtained in the presence of simple synthetic ligands. An improved fit between experimental observations and Pb speciation was obtained by taking into account the formation of a ternary complex at the algal surface. The contribution of the ternary complexes to Pb bioaccumulation was dependent on the relative binding constants of the Pb to the NOM and to the binding sites on the biological surface. In the presence of the humic acid, a decreased surface charge and increased membrane permeability were considered to be of secondary importance to explain the observation of increased Pb uptake with respect to that predicted on the basis of [Pb 2+ ]. The environmental implications of the results are discussed with respect to the development of site-specific water quality criteria.

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“…Laboratory-based experimental work, mainly with well-characterised pre-isolated fulvic and humic acids, demonstrated the key yet dual role of the DOM in metal uptake by algae. Humic substances decrease metal uptake by complexing metals in the medium, [7][8][9][10][11][12][13] but they can increase the adsorbed or internalised metal by adsorbing to the algal surfaces, [14][15][16] enhancing the negative charge [11,14,16] and adding additional binding sites on the algal cell surface that were proposed to contribute to increased Pb uptake. [11,12] A non-humic fraction, for example extracellular polymeric substances, representing up to 25% of DOM in natural waters [17] has received very little attention in metal uptake studies.…”

Section: Introductionmentioning

confidence: 99%

Pb uptake by the freshwater alga Chlorella kesslerii in the presence of dissolved organic matter of variable composition

Lamelas¹

2008

Environ. Chem.

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Environmental context. Dissolved organic matter (DOM) is of utmost importance for a toxic metal's fate and ecotoxicity in the aquatic system, but the complex nature and variable composition of DOM makes the quantitative understanding of DOM's role in the environment very difficult. We have demonstrated that the assumption that the properties of a DOM mixture are the sum of the properties of its individual fractions can capture the main trends characterising the role of DOM in lead speciation and adsorption by freshwater microalgae. This was done by mixing the isolated, well-characterised fractions of DOM and measuring levels of free lead ion and Pb adsorbed and internalised by algae.Abstract. Dissolved organic matter (DOM) is a complex mixture of ill-defined components, which makes the quantitative understanding of DOM functions in aquatic systems a challenging task. The traditional approach for studying such complex mixtures involves their separation into groups of different components, while assuming minimal or no alteration of their properties. By mixing the pre-isolated and well-characterised individual fractions of the DOM, including humic, fulvic and alginic acids, we have demonstrated that the free Pb ion concentrations and the adsorbed Pb plus Pb internalised by the alga Chlorella kesslerii in the presence of DOM samples of different compositions can be predicted on the basis of the experiments performed in the presence of the individual DOM fractions. An additivity model assuming that the properties of the mixture can be considered as the sum of the properties of the individual components captured the Pb speciation and adsorption behaviour in the presence of DOM of variable compositions. Similarly to the results with the individual DOM fractions, internalised Pb concentrations in the presence of the reconstituted DOM were greater than that predicted by the corresponding free lead ion concentration. An improved fit between experimental observations and the model predictions of adsorbed plus internalised Pb in the presence of DOM of different compositions was observed by assuming that each individual component adsorbed by the algae gave access to additional binding sites for Pb. Furthermore, the contribution of the Pb-DOM complex to total cellular Pb was dominated by the humic and fulvic acids, whereas the contribution of alginate was minimal.

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Permeability Changes in Model and Phytoplankton Membranes in the Presence of Aquatic Humic Substances

Cited by 198 publications

References 21 publications

Effect of Humic Acid on Cd(II), Cu(II), and Pb(II) Uptake by Freshwater Algae: Kinetic and Cell Wall Speciation Considerations

Effect of Humic Acid on Cd(II), Cu(II), and Pb(II) Uptake by Freshwater Algae: Kinetic and Cell Wall Speciation Considerations

Influence of the Composition of Natural Organic Matter on Pb Bioavailability to Microalgae

Pb uptake by the freshwater alga Chlorella kesslerii in the presence of dissolved organic matter of variable composition

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