Speciation of Cu, Pb, Cd and Hg in waters of the Oporto coast in Portugal, using pre-concentration in a Chelamine resin column 1

Sea water was collected monthly between January and March 1996 from the shore of the Oporto coast at three different representative sampling points and speciation of Cu, Pb, Cd and Hg were carried out. For the purpose, total particulate (retained on a 0.45 μm pore-size filter), particulate sorbed to inorganic matter, total dissolved, and dissolved and operationally labile metal was discriminated. The filters were digested by microwaves. The filtered water was pre-concentrated on a microcolumn of Chelamine, eluted with 5 ml of 2 mol l−1 HNO3 and analysed by flame atomic absorption spectrometry (F-AAS) or mercury cold vapour (MCV-AAS) for Hg. Spike recovery percentages did not differ significantly (P>0.05) from 100% for any metal studied. The organic matter (OM) destruction was performed by UV photolysis. For quality control of the results, determination of Cu, Pb and Cd total dissolved concentration by differential pulse anodic stripping voltammetry was also performed; for Hg only the pre-concentration in the column was changed to partial evaporation of the sea water, followed by MCV-AAS. No statistically significant difference was observed between the results provided by the comparative methods. Online pre-concentration with Chelamine showed to be expeditious and effective for extraction of the heavy metals in coastal waters. The distribution of each metal in the different fractions, including ascertainment of significant correlation between pairs of metal fractions and the respective partition coefficients, is discussed.