Abstract
The uptake of nutrients or toxicants by different organisms in aquatic systems is known to correlate with different fractions of the nutrient's or toxicant's total concentration. These fractions can be provided by different analytical techniques, from which the better correlation is expected to be found for those with a characteristic length comparable to that in the considered organism uptake. An effective concentration signature can be built up with the concentration values associated to the availability (i.e. fluxes in dynamic techniques) of the nutrient or toxicant measured by various analytical techniques with different characteristic lengths. Here, this new representation was obtained for the pool of Zn complexes in the Mediterranean stream Riera d'Osor (Girona, Catalonia, Spain) with a suite of four analytical techniques. Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) and Polymer Inclusion Membrane (PIM) devices provided the free Zn concentration. Linear Anodic Stripping Voltammetry provided a labile fraction (defined here as cLASV, higher than the free concentration), related to the diffusion layer scale. Diffusion Gradients in Thin-films provided higher labile fractions (known as DGT concentrations, cDGT) connected to the different characteristic lengths of different configurations (e.g. one or two resin discs) longer, in any case, than that corresponding to LASV. The combination of the information retrieved by the techniques allowed to quantify lability degrees of the pool of Zn complexes and to build up the effective concentration signature for this water.
Highlights
No single analytical technique – applied to the medium- can claim to provide a complete description of the availability of the metal in such a medium for all organisms, because each analytical technique accesses to a window of the total information, usually related to some characteristic length of its sensor (Sigg et al, 2006; van Leeuwen et al, 2005)
The main aim of this paper is to present the “effective concentration signature” as an integration of the measurements obtained with the different techniques, based on the comparison of the available concentrations retrieved by each one of the techniques
The total Zn concentration for the sample analysed with AGNES and LASV was 6.33 × 10−7 mol L−1
Summary
The dynamics can be modulated by the length of the path to be followed by the metal species from the bulk of the medium towards the active surface of the biota. No single analytical technique – applied to the medium- can claim to provide a complete description of the availability of the metal in such a medium for all organisms, because each analytical technique accesses to a window of the total information, usually related to some characteristic length of its sensor (Sigg et al, 2006; van Leeuwen et al, 2005). The more techniques (with different characteristics) contribute with their specific information, the more complete the resulting picture of the metal availability in the medium will be
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