Performance of diffusion gradient in thin films to evaluate the toxic fraction of copper to Daphnia magna

Abstract

This study investigates the relevance of the diffusion gradient in thin films technique (DGT) to measure copper's induced lethality on Daphnia magna in natural water spiked with various organic ligands. Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and glycine were used as artificial organic ligands in controlled solutions of mineral water. With EDTA, DGT measurement makes it possible to predict the toxicity of the mixture because Cu-EDTA complexes are inert, whereas DGT is of no help in the case of NTA, because Cu-NTA complexes are fully labile. The Cu-glycine complexes appear as partly labile and toxic. Humic acids as well as fresh and aged algae extracts also were used as models for natural dissolved organic matters. All three of them form copper complexes that are not toxic to Daphnia magna and appear as partly labile with open-pored DGT. However, the use of restricted gels in DGT greatly reduces the contribution of labile complexes, at least for humic acids and aged algae copper complexes. The DGT with restrictive gels, therefore, appears to be a powerful tool for measuring bioavailable copper in natural water bodies, especially when the dissolved organic matter mostly is of humic origin. The DGTs potential ability to mimic the lability induced by the biological uptake also is discussed.

Trace Metal Concentrations in an Intensive Agricultural Watershed in British Columbia, Canada1

“…, 2005; Buzier et al. , 2006) and can be manipulated with different binding gels to measure a variety of complexing ligands if necessary (Tusseau‐Vuillemin et al. , 2004; Li et al.…”

Progress in understanding the use of diffusive gradients in thin films (DGT) – back to basics

“…[39,51,52] To our knowledge the binding of simple organic ligands has not been directly tested, although measurements of metals by DGT in solutions where they are present have been sensibly interpreted without invoking such effects. [56][57][58] An experimental study has considered directly the enrichment in an APA gel of Suwannee River fulvic acid (SRFA) and humic acid extracted from forest soil (FSHA). Deployment solutions were buffered with the sodium salt of 2-(N-morpholino)ethanesulfonic acid (MES) to pH 6.1 and contained NaNO 3 (0.001-0.1 M).…”

Mobility and bioaccessibility of trace metals in soils assessed by conventional extraction procedures and passive diffusive samplers

“…As numerous experiments show that the biological effects of trace metals are related to the free metal ion activity (Allen et al, 1980;Tusseau-Vuillemin et al, 2004), it has been advantageous for researchers to utilise DGT techniques to measure labile metal species as a means to understand the bioaccessible metal fraction.…”