| Autor: |
Mueller, Kristin K., Couture, Raoul-Marie, Fortin, Claude, Campbell, Peter G. C. |
| Předmět: |
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| Zdroj: |
Environmental Chemistry (14482517); 2024, Vol. 21 Issue 1, p1-13, 13p |
| Abstrakt: |
Environmental context: Natural dissolved organic matter strongly influences the biogeochemistry and bioavailability of trace metals in natural waters. Chemical equilibrium models are often used to predict the relative importance of the free metal cation, a recognised indicator of the metal's bioavailability. Here we show how the nature of the organic matter varies between two lakes, affecting the measured speciation of copper and nickel, a result that challenges existing chemical equilibrium models. Rationale: Thermodynamic models such as the Windermere Humic Aqueous Model (WHAM) are often used to estimate the binding of cations by dissolved organic matter (DOM) in natural aquatic systems. Such models require as input data the quantity of DOM but do not consider its quality. Using two well-characterised lakewater samples, we demonstrate, for realistic environmental conditions, that the conditional binding parameters for the complexation of Ni and Cu with natural DOM vary between lakes and we relate these differences to the spectroscopic quality of the DOM. Methodology: Waters from two lakes with contrasting types of DOM were titrated with Cu and Ni and the conditional binding parameters were calculated using a two-site ligand model, with associated conditional stability constants implemented in PHREEQC v.3.1.2, and compared between lakes and between metals. The titration curves for each lake were compared to those predicted by WHAM v7.05. Results: Binding affinities and capacities of DOM for Cu and Ni were found to differ not only between metals, but also between lakes. Discussion: Overall, the titration results suggest that the more aromatic humic-like DOM from allochthonous sources may have a significantly higher complexation affinity for Ni than the more protein-like DOM from autochthonous sources. The differing behaviour of Ni and Cu in the two lakes suggests that they are binding to different types of binding sites within the DOM matrix. More data with various natural DOM samples are needed to capture the diversity of metal–DOM interactions and to improve our ability to predict metal speciation in natural waters. Environmental context. Natural dissolved organic matter strongly influences the biogeochemistry and bioavailability of trace metals in natural waters. Chemical equilibrium models are often used to predict the relative importance of the free metal cation, a recognised indicator of the metal's bioavailability. Here we show how the nature of the organic matter varies between two lakes, affecting the measured speciation of copper and nickel, a result that challenges existing chemical equilibrium models. This article belongs to the collection Dedication to Prof. Edward Tipping. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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