HEAVY-METAL LOAD OF SEDIMENTS OF THE RIVER GURK (CARINTHIA AUSTRIA) -MERITS AND LIMITATIONS OF SEQUENTIAL LEACHING

By means of the analysis of sediments cored in the small river Gurk (C arinthia/Austria), the input of Ag, Cd, Ce, Cr, Hg, La, Mo, Ni, V, and W from a chemical industrial plant could be detected. To estimate the actual load, and to obtain data for comparison with other sites, both unsieved fine sediments and sediments sieved to 20 mum were investiga ted from the same cores. Environmental mobilities of toxic heavy metal s (Co, Cr, Cu, Ni, Zn) have been shown by sequential leaching followin g Tessier/Forstner. In the last step, HNO3 leaches a purely geogenic f raction, which is fairly constant along the investigated river. Wherea s the additional Cr from the input of the chemical plant is mainly fou nd in the oxalate-leachable fraction, short-time-load to unpolluted se diments in the laboratory is found mainly in hydroxylamine/acetic acid . Both is due to the high affinity of Cr to Fe- and Mn-oxides. Adsorpt ion/desorption experiments reveal that the low carbonate content of th e Gurk sediments increases the importance of Fe/Mn-oxides for the sorp tion of Cr compared to other samples containing carbonate. The Ni-load was primarily found in weak-acid-leachable and oxalate-leachable frac tions. Similarly, the oxalate-leachable fraction is dominant for adsor ption of other metals and phosphorus. Other inter-element relationship s among the amounts leached, which are attributable partly to carbonat e-, silicate-, organic or coating phases, have been found by means of factor analyses together with marker fractions for each type.