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In Situ Speciation Measurements of Trace Metals in Headwater Streams

Warnken, Kent W.; Lawlor, Alan J.; Lofts, Stephen; Tipping, Edward; Davison, William; Zhang, Hao. 2009 In Situ Speciation Measurements of Trace Metals in Headwater Streams. Environmental Science & Technology, 43 (19). 7230-7236. 10.1021/es900112w

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Abstract/Summary

Concentrations of Al, Fe, Mn, Ni, Cu, Cd, Pb, and Zn were measured using DGT (diffusive gradients in thin-films) devices deployed in situ in 34 headwater streams in Northern England. Mean values of filtered samples analyzed by ICP-MS (inductively coupled plasma mass spectrometry) were used, along with DOC (dissolved organic carbon), pH and major ions, to calculate the distribution of metal species using the speciation code WHAM. DGT-measured concentrations, [Me]DGT, of Zn and Cd were generally similar to concentrations in filtered samples, [Me]filt. For the other metals, [Me]DGT was similar to or lower than [Me]filt. Calculation of the maximum dynamic metal from the speciation predicted using WHAM showed that most of the lower values of [Cu]DGT could be attributed to the dominance of Cu−fulvic acid complexes, which diffuse more slowly than simple inorganic species. Similar calculations for Al, Pb, and Mn were consistent with appreciable proportions of these metals being present as colloids that are not simple complexes with humic substances. Differences between WHAM predictions and the measured [Ni]DGT indicated that WHAM used with the default binding parameters underestimates Ni binding to natural organic matter. Plots of [Me]DGT versus the ratio of bound metal to DOC provided slight evidence of heterogeneous binding of Pb and Cu, while results for Mn, Cd, and Zn were consistent with weak binding and complete lability.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1021/es900112w
Programmes: CEH Topics & Objectives 2009 onwards > Biogeochemistry > BGC Topic 2 - Biogeochemistry and Climate System Processes > BGC - 2.1 - Quantify & model processes that control the emission, fate and bioavailability of pollutants
CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon > BG01.4 Metals
CEH Sections: Shore
ISSN: 0013-936X
NORA Subject Terms: Ecology and Environment
Earth Sciences
Chemistry
Date made live: 09 Dec 2009 16:35
URI: http://nora.nerc.ac.uk/id/eprint/7481

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