Trace metals in the open oceans: Speciation modelling based on humic-type ligands

Anthony Stockdale, Edward Tipping, John Hamilton-Taylor, Stephen Lofts

Research output: Contribution to journalArticlepeer-review


The speciation of trace metals in the oceans is typically explained by invoking the concept of metal binding to specific organic ligands, but a lack of detailed knowledge about the ligands has impeded the formulation of comprehensive models to predict speciation chemistry. The aim of our study was to shed further light on the possible role of humic-type ligands in trace metal complexation in the oceans by comparing published seawater (open ocean) speciation measurements with predictions obtained using a speciation model typically used for freshwater and soil systems (Windermere Humic Aqueous Model; WHAM). We show that in some cases, speciation of trace metals in seawater environments may be reasonably predicted using this model with its default parameter set, without any model fitting. The results support the idea that humic-type ligands may account for much of the observed organic binding at least in the cases of Fe, Cu and Pb. Although the model does not consistently provide agreement with the measured values, it provides a useful benchmark to compare different datasets and to examine variation in speciation as a result of varying levels of competing metal ion concentration and fulvic acid activity.

Original languageEnglish
Pages (from-to)304-319
Number of pages16
JournalEnvironmental Chemistry
Issue number3
Publication statusPublished - 29 Jun 2011
Externally publishedYes


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