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Kinetic signatures of metals in natural waters

Jacqui Levy, LEC

Friday 25 February 2011, 1300-1400
LEC Training Room 1

Centre for Sustainable Water Management Seminar

Metal-organic matter interaction is a key process controlling metal bioavailability in aquatic systems. Fulvic acid is often the dominant form of dissolved organic carbon (DOC) in freshwater systems, but aquagenic organic carbon (e.g. carbohydrates and proteins released by algae and bacteria) can also make up a significant fraction of DOC, particularly in productive lakes. Diffusive Gradients in Thin-films (DGT) is a dynamic technique that can measure metal speciation in situ. Free and labile metals diffuse through a polyacrylamide gel layer and are consumed at the resin binding layer. This creates a concentration gradient and the steady flux of metal from an aquatic system can be measured. DGT can also be used to derive information on kinetics. By looking at the metal-complex exchange kinetics for many metals at once, kinetic signature plots can be derived, and information about the rate of dissociation and/or strength of metal binding may then be evaluated. In this work we used DGT to look at the kinetics of metals dissociation in the laboratory, with fulvic acid and algal exudates, and in the field for a variety of waters with different pH, DOC and metal concentrations.