MICROANALYTICAL DETERMINATION OF METALLIC CONSTITUENTS OF RIVER SEDIMENTS

The distribution of metallic constituents in torrential rivers as a function of the size particle cannot be frequently achieved by conventional analytical procedures, because of the lack of sufficient amounts of the fine fractions. For the study of river sediments in the Basque Country, microanalytical methods have been developed both for major (Na, K, Ca, Mg, Fe, Al, Si) and trace (Cu, Zn, Mn, Cr, Pb, Ni, Cd) components. Wet digestion in PTFE vessels at 140-degrees-C was done with 0.05 g sample using HNO3-HClO4-HF-H3BO3 or HNO3-HClO4, respectively. Further determinations were made by i) emission spectrometry (Na, K), ii) visible spectrophotometry (Al), iii) FIA (Fe, Si) and iv) AAS with flow spoiler (Ca, Mg, Cu, Zn, Mn) or graphite furnace (Cr, Pb, Ni, Cd). The proposed method has been checked with a standard sample obtaining mean values almost coincident with the certified ones and variation coefficients lower than 2% for major and 8% for trace components. Then it was applied to total samples and the fine fractions (< 63-mu-m) of 26 samples of sediments from three torrential rivers. Replicated values with analogous variation coefficients were obtained. Some considerations on distribution of major and trace constituents as a function of particle size are also included.