Metals in Main Rivers of Azerbaijan: Influence of Transboundary Pollution

Silver, arsenic, cadmium, chromium, cobalt, copper, mercury, lead, and zinc were determined monthly during 2004–2008 at 11 sites in the Kura–Araks river system, Azerbaijan. Suspended fractions of the elements were studied at the five sites experiencing the highest load. Metal concentrations varied moderately at each site but differed substantially between sites. Sites near the borders with Armenia and Georgia were most polluted, both with respect to soluble concentrations and percentage transported in suspended form. Lower parts of the Kura river were shielded from metal contamination by an upstream reservoir acting as a metal trap. Corresponding removal was not evident in Araks, its main tributary, where particularly high concentrations of arsenic were observed. At the most contaminated sites, more than 60% of cadmium, cobalt, chromium, copper, manganese, nickel, lead, and zinc was transported in suspended form whereas arsenic and molybdenum occurred mainly in soluble form. Dynamics of metals in the Kura–Araks water/sediment system should be further studied to meet future problems.