Towards a new method for labile metal assessment in aquatic environments [Vers une nouvelle méthode de détermination des métaux labiles dans les milieux aquatiques]

Abstract : It is now recognized that in order to evaluate the impact of metals on living organisms in aquatic systems, it is necessary to assess the bioavailable fraction of metal. Several techniques exist such as the DGT method (Diffusive Gradient in Thin Film) which allows the measurement of the labile fraction of metal complexes. However, this method is by nature an integrative approach and is not suitable for spot measurements of labile metals. The objective of this study, conducted by the Leesu in collaboration with Siaap, is to optimize and to validate a simple method for the determination of labile metal concentrations in aquatic systems. For this, we chose the use of chelating disks made of a polymer (polystyrene divinylbenzene) functionalized with imino-diacetic acid (IDA) which are chelating groups similar to those used by the DGT method. The originality here is to use these chelating groups in chelating disks which can be used just like ordinary filter discs. The filtered sample is introduced into the chelating disk, IDA groups retain labile metal by complexation. The concentration of "inert" metal is determined in the disk effluent and provides access to the concentration of labile forms by subtracting from total dissolved metal. This principle is very simple and is compatible with spot measurements.