Copper and nickel speciation in mine effluents by combination of two independent techniques.

To control potentially toxic metals in water resources it is necessary to know metal speciation and changes in the metal speciation that occur after aqueous effluents containing metals are discharged into freshwaters. This work explores the speciation of nickel and copper in metal-mining aqueous effluents. Diffusive gradients in thin films (DGT) technique and competing ligand exchange (CLE) method have been applied to determine the speciation of nickel and copper. The results of this investigation demonstrate that combination of two analytical techniques having complementary analytical capabilities can provide a better physicochemical picture of metal speciation than either one of the analytical technique can do alone. The combined use of these techniques revealed that copper formed labile complexes having slow diffusion coefficient along with the presence of small labile copper complexes. Nickel-dissolved organic complexes (DOC) complexes in the aqueous effluent have been found to have fast diffusion coefficient. The results are likely to have environmental significance for providing a link between the metal species in mine aqueous effluent and their bioavailability by determining the characteristics of copper and nickel complexes in metal-mine aqueous effluents. This knowledge is expected to promote a better understanding of the lability of DOC complexes of copper and nickel in mining effluents.