In situ Measurement of Trace Metals in Estuarine Waters of Patos Lagoon using Diffusive Gradients in Thin Films (DGT)

The diffusive gradients in thin-films (DGT) technique was used to determine labile metals in situ during different hydrological conditions in the Patos Lagoon estuary. Water samples were also analyzed for Chelex-labile fractions of Cd, Co, Cu, Mn, Ni and Zn using Chelex-100 resin. DGT-labile concentrations of Cd, Cu, Ni and Zn were lower than Chelex-labile concentrations, possibly because colloids were trapped in the Chelex resin column. There was a decrease with increasing deployment time in the concentrations of all elements measured by DGT, reflecting changes in metal speciation in solution caused by the decrease in the salinity and associated with change in pH in the estuary. The results demonstrated the sensitivity of DGT to metal speciation and the feasibility of using the DGT technique in highly dynamic estuarine waters to obtain a time-integrated record of labile trace metals.