Tipping, E, Lofts, S and Stockdale, A (2015) Metal speciation from stream to open ocean: modelling v. measurement. Environmental Chemistry, 13 (3). pp. 464-477. ISSN 1448-2517
Abstract
We compiled a data set of ~2000 published metal speciation measurements made on samples of fresh waters, estuarine and coastal waters, and open ocean waters. For each sample, we applied the chemical speciation model WHAM7 to calculate the equilibrium free metal ion concentrations, [M] (mol L–1), amounts of metal bound by dissolved organic matter (DOM), ν (mol g–1), and their ratio ν/[M] (L g–1), which is a kind of ‘local’ partition coefficient. Comparison of the measured and predicted speciation variables for the whole data set showed that agreements are best for fresh waters, followed by estuarine and coastal waters, then open-ocean waters. Predicted values of ν/[M], averaged over all results for each metal, closely follow the trend in average measured values, confirming that metal reactivity, and consequent complexation by DOM, in natural waters accord with the expectations of the speciation model. Comparison of model predictions with measurements by different analytical techniques suggests that competitive ligand–stripping voltammetry methods overestimate metal complexation by DOM, and therefore underestimate [M]. When measurements by other methods are compared with predictions, for all metals, reasonable agreement with little bias is obtained at values of ν > 10–6 mol g–1 DOM, but at lower values of ν, the model predictions of [M] are mostly higher than the measured values, and the predictions of ν and ν/[M] are mostly lower. Research is needed to establish whether this reflects analytical error or the failure of the model to represent natural high-affinity ligands.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015, CSIRO Publishing. This is an author produced version of a paper published in Environmental Chemistry. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 09 Oct 2015 13:43 |
Last Modified: | 14 Apr 2017 04:00 |
Published Version: | http://dx.doi.org/10.1071/EN15111 |
Status: | Published |
Publisher: | CSIRO Publishing |
Identification Number: | 10.1071/EN15111 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:90599 |