In the coastal areas of Finland and Sweden, widespread acid sulphate soil occurrences (c. 4760 km2), developed on artificially drained Holocene sulphide-bearing sediments, are causing serious environmental problems, such as acidification and metal contamination of surface waters, hydrobiological damage and elemental imbalance in crops. In this study, five acid sulphate soil profiles were geochemically characterized and compared with existing hydrogeochemical data in order to find evidence of the behaviour of a variety of trace elements in catchments affected by these soils. The results show that Cd, Co, Ni, Y and Zn are depleted in the acid sulphate soils and enriched in the recipient streams, whereas As, Ga, Mo, Nb, Pb, Sb, Sc, Ti and Zr are not depleted in detectable amounts in these soils and are not (or only weakly) enriched in the recipient streams. It is concluded that the former group is highly mobile in the acid sulphate soils and thus lost to adjacent drains in substantial amounts, whereas the latter group is moderately to highly immobile in these soils and is thus leached in background amounts only. The approach is possible to use in similar areas elsewhere, i.e. where oxidation and weathering of soils or overburden significantly affect the surface-water quality.

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