DISCRIMINATION BETWEEN CR(VI) AND CR(III) LOAD BY SEQUENTIAL LEACHINGMETHODS

Freshwater sediments from Austrian rivers as well as clays and soils w ere spiked with Cr(III) or Cr(VI) by shaking them overnight with non-a cidified tap water. Whereas the adsorption of Cr(III) was quantitative , chromium(VI) adsorption depended on the sample composition, especial ly on the organic carbon contents. The desorption of chromium from spi ked and non-spiked samples was investigated by two independent sequent ial leaching methods. The resulting leaching patterns depended on the original form of the chromium species as well as on the main component s of the solids. Whereas the Cr(VI) spike was partially desorbed by am monium chloride, the displacement of Cr(III) was negligible. Contrary to this, in a leaching sequence starting with ammonium acetate pH 7 an d followed by ammonium acetate pH 5, the differences in the release pa tterns of both spikes were small. In the leaching sequences applied, m ajor parts of the spikes were found in 0.5M HCl, or in hydroxylamine/2 5% acetic acid. From the original sample, hot HNO3 mobilized the same amounts than from the spiked ones. Some of the Cr-spikes moved to frac tions not leachable without HF.