ESTIMATION OF OCCURRENCE AND SPATIAL DISTRIBUTION OF HEAVY METALS IN OHRID AND PRESPA LAKES, ALBANIA

The occurrence and distribution of some heavy metals in waters of Ohrid and Prespa lakes were investigated by means of their content determination in the water column. Different anthropogenic pressures, especially heavy metal originating from mining activities might have influenced the fragile equilibrium of the lakes ecosystem. Heavy metal concentrations in water were investigated at selected sites of both lakes. A total of 19 samples of water have been collected and the dissolved fraction of heavy metals such as Fe, Cr, Ni in the water was measured using the GF-AAS technique. According to the results obtained, Fe (52.7-1.6 ?g.L-1), Cr (17.9-0.9 ?g.L-1) and Ni (12.2-3.6 ?g.L-1) were found in high content in the surface and bottom waters of Ohrid and Prespa lakes, (NIVA, 2000). Compared to Ohrid Lake, Prespa Lake was characterized by a lower presence of heavy metals in its waters. Apparent variations of metal content in different depths of each station were evident especially for Fe, assuming that their dissolved fraction is very dependent of lake water factors such as redox potential, presence of other ions as well as water stratification.