Abundance and fractionation patterns of rare earth elements in streams affected by acid sulphate soils

The abundance and shale-normalised fractionation patterns of rare earth ele ments (REEs) were studied in 121 streams of first and second order in an ar ea where acid sulphate soils. developed on oxidised sulphide-bearing marine sediments. are abundant. During high-water flow events in autumn, on which this study focuses, the leaching of REEs from the acid sulphate soils is e xtensive, resulting in high total REE concentrations (up to > 1 mg/l) in st reams draining such soils exclusively. In these streams, there is a general depletion of the heavy REEs explained by preferential scavenging of the la tter by oxyhydroxides in the deepest soil-profile horizons. In streams drai ning areas of glacial till and peat, the REE concentrations are several ord ers of magnitude lower. In these streams, in contrast to the REE-enriched s treams, there is a depletion of light REEs explained most likely by prefere ntial complexation of the middle and heavy REEs by dissolved humic substanc es. (C) 2001 Elsevier Science B.V. All rights reserved.