Abstract

The extent of pollution was investigated in sediments collected along the course of the river Meža and its tributaries in the lead and zinc mining area of the Mežica valley (Slovenia). In order to evaluate the heavy metal burden, total concentrations of Zn, Pb and Cd were determined and the partitioning of these metals between the easily and sparingly soluble sediment fractions was performed by the use of the slightly modified BCR sequential extraction procedure. The quality of analytical data was checked with Certified Reference Material CRM 601. Good agreement between the determined and certified or indicative metal concentrations was obtained. In order to estimate the natural and anthropogenic inputs of Zn, Pb and Cd in the sediments, normalisation to Al was applied. The results of the partitioning study indicate that Zn prevails in the most sparingly soluble fraction and is distributed between organic matter and sulfides, while a smaller proportion is found in the easily soluble fraction. Pb is distributed mainly between organic matter and sulfides, whereas Cd is predominantly associated with the most sparingly soluble fraction. Data from the normalisation procedure indicate that the anthropogenic inputs of Zn, Pb and Cd correlate with the very high total metal concentrations determined in sediments. The highest total Zn, Pb and Cd concentrations (16.3, 9.3 and 0.13 g kg⁻¹, respectively) were found in the sediment of the Helena rivulet, arising from former mining activities. In spite of the relatively low easily soluble metal fractions in the sediment, the concentrations of metals in these fractions are high, owing to the extremely high total metal concentrations. These data indicate severe pollution of the terrestrial and aquatic environment.