Measurement of Free Cu Ion Activity in Seawater Using a Passive-Equilibrium Sonic-Assisted Free Ion Recorder (SAFIR)

2011 ◽  
Vol 45 (13) ◽  
pp. 5660-5667 ◽  
Author(s):  
Li Li ◽  
Franco Pala ◽  
Jaclyn Haskins ◽  
Katrina Sukola ◽  
Gordon T. Wallace
Keyword(s):  
Free Ion ◽  
Ion Activity

scholarly journals When are metal complexes bioavailable?

2016 ◽  
Vol 13 (3) ◽  
pp. 425 ◽  
Author(s):  
Chun-Mei Zhao ◽  
Peter G.C. Campbell ◽  
Kevin J. Wilkinson
Keyword(s):  
Metal Complexes ◽  
Biotic Ligand Model ◽  
Metal Bioavailability ◽  
Biotic Ligand ◽  
Free Ion ◽  
Ion Activity ◽  
Classical Models ◽  
Kinetic Processes ◽  
Free Metal ◽  
Ligand Model

Environmental contextThe concentration of a free metal cation has proved to be a useful predictor of metal bioaccumulation and toxicity, as represented by the free ion activity and biotic ligand models. However, under certain circumstances, metal complexes have been shown to contribute to metal bioavailability. In the current mini-review, we summarise the studies where the classic models fail and organise them into categories based on the different uptake pathways and kinetic processes. Our goal is to define the limits within which currently used models such as the biotic ligand model (BLM) can be applied with confidence, and to identify how these models might be expanded. AbstractNumerous data from studies over the past 30 years have shown that metal uptake and toxicity are often best predicted by the concentrations of free metal cations, which has led to the development of the largely successful free-ion activity model (FIAM) and biotic ligand model (BLM). Nonetheless, some exceptions to these classical models, showing enhanced metal bioavailability in the presence of metal complexes, have also been documented, although it is not yet fully understood to what extent these exceptions can or should be generalised. Only a few studies have specifically measured the bioaccumulation or toxicity of metal complexes while carefully measuring or controlling metal speciation. Fewer still have verified the fundamental assumptions of the classical models, especially when dealing with metal complexes. In the current paper, we have summarised the exceptions to classical models and categorised them into five groups based on the fundamental uptake pathways and kinetic processes. Our aim is to summarise the mechanisms involved in the interaction of metal complexes with organisms and to improve the predictive capability of the classic models when dealing with complexes.

A Comparison of Copper Speciation Measurements with the Toxic Responses of Three Sensitive Freshwater Organisms

2005 ◽  
Vol 2 (4) ◽  
pp. 320 ◽  
Author(s):  
Simon C. Apte ◽  
Graeme E. Batley ◽  
Karl C. Bowles ◽  
Paul L. Brown ◽  
Nicola Creighton ◽  
...  
Keyword(s):  
Organic Matter ◽  
Natural Water ◽  
Natural Waters ◽  
Copper Toxicity ◽  
Copper Ion ◽  
Fresh Waters ◽  
Total Copper ◽  
Free Ion ◽  
Ion Activity ◽  
Toxic Responses

Environmental Context.A rapid Chelex resin method is shown to be a valuable speciation screening tool for use in a tiered risk assessment of copper toxicity in fresh waters. It is a more conservative measure than toxicity testing with sensitive biota, but a better indicator of toxicity than a dissolved copper measurement. Abstract.Twelve natural fresh waters with similar pH and hardness, but varying dissolved organic carbon (DOC) and copper concentrations, were assessed for (a) toxicity to an alga (Chlorella sp. 12), a cladoceran (Ceriodaphnia cf. dubia) and a bacterium (Erwinnia sp.), and (b) copper speciation using a rapid Chelex extraction method, diffusive gradients in thin films (DGT) and anodic stripping voltammetry (ASV). In synthetic fresh water with no added DOC, at pH 7.0 and low hardness, the toxic responses (EC/IC50) of all three organisms to copper were similar. However, in the toxicity of copper added to natural water samples exhibited a negative linear relationship to DOC (r2 = 0.82–0.83), with respective slopes for algae, cladocerans and bacteria decreasing in the ratio 7.4 : 3.5 : 1. The marked difference in responses in the presence of natural dissolved organic matter indicated that not all of the organisms conformed to the free ion activity model (FIAM). This was confirmed by copper ion selective electrode measurement of copper ion activity. Copper toxicity to algae in the presence of DOC was overestimated by free ion activity possibly due to surface binding of DOC. Copper toxicity to the bacteria was greater than predicted and was shown to be a result of bioavailability of some copper complexes formed with organic matter. Cladocerans appear to more closely follow FIAM predictions. These findings have important implications for attempts to extend predictive models of metal toxicity beyond fish to more sensitive freshwater species. The measured labile copper concentrations of copper-spiked natural waters varied from 0 to 70% of total copper concentrations. There was no clear relationship between the three measurement techniques. Good correlations were obtained between both algal and bacterial growth inhibitions measured on copper-spiked natural waters and the corresponding Chelex-labile copper concentrations. A single natural water sample was manipulated to different pH and hardness values, spiked with copper, and tested using the above three organisms with the Chelex method. Toxicity test results generally agreed with studies performed in synthetic fresh waters, showing that the relationships between toxicity, pH and hardness were organism-specific. Chelex-labile copper was always over-predictive of toxicity but significantly better (P ≤ 0.05) than dissolved copper concentrations, as it only detects the fraction of total copper that is reactive over biologically-relevant timescales. Colloidally-bound copper and copper associated with strong ligands are not detected. The Chelex method is therefore useful as a measure where speciation is accepted in water quality regulations.

Evaluating a ‘Free Ion Activity Model’ applied to metal uptake by Lolium perenne L. grown in contaminated soils.

2005 ◽  
Vol 270 (1) ◽  
pp. 1-12 ◽  
Author(s):  
R. L. Hough ◽  
A. M. Tye ◽  
N. M. J. Crout ◽  
S. P. McGrath ◽  
H. Zhang ◽  
...  
Keyword(s):  
Lolium Perenne ◽  
Contaminated Soils ◽  
Metal Uptake ◽  
Activity Model ◽  
Lolium Perenne L ◽  
Free Ion Activity Model ◽  
Free Ion ◽  
Ion Activity
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