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Abstract: By directly assessing, through atomic absorption spectrometry (AAS), the heavy metals and the arsenic contents of natural water-flows that cross regions where large-scale mining activities are carried out, there are quite accurately estimated the corresponding amounts of contamination. The present paper describes the methodology which was employed in order to assess the contents of Mn, Fe, Cu and Zn, by means of flame-AAS, and the contents of Cr, Co, Ni, Cd, Al, Pb, Sb and As, by means of direct electrothermal-AAS. The analytical methods which had been developed have been further utilized in surveying the chemical composition of an almost 110 km long stream section of Arieş river, by considering water samples collected both from the surface flow, and from the adjoining hyporheic zone. The experimental activities managed to identify two distinct regimes, one that was relatively normal in terms of contaminants distribution and, in contrast, one episode of severe pollution. Through the adopted approach there was ascertained that also the hyporheic zone was contaminated with heavy metals carried by the stream Arieş, yet the corresponding concentration levels were significantly smaller, the latter circumstance outlining the role played by that zone in the processes of self-decontamination.

Keyword: hyporheic zone, heavy metals, atomic absorption spectrometry, surface water, mining area, Arieş