Metals in grain fractions of bottom sediments from selected rivers in north-eastern Poland

The studies carried out in March 2006 aimed at evaluating the distribution of total and labile forms of Cd, Pb, Zn, Cr, Ni, Cu and Co in grain fractions (mm): 1.0–0.2; 0.2–0.1; 0.1–0.063; <0.063 of bottom sediments from the upper Narew river and some of its tributaries. The studies were performed also to find out which fractions are mostly responsible for sediment contamination. Metal concentrations were determined by means of atomic absorption spectrometry (AAS) technique. It was found that the contents of lead, zinc, chromium, nickel, copper and cobalt both in total and labile forms increased along with the decrease of particle size. Our investigation revealed that bottom sediments in the upper Narew river and in its tributaries contained low concentrations of the studied metals.