Background: The Zayandeh Rud, as a main river in the center of Iran, is the most important source of water for irrigation, industrial development and municipal use. The aim of this study was to evaluate the changes in contamination of Zayandeh Rud sediments.

Materials and Methods: Samples were taken from the 6 stations along the river. Electrical conductivity, pH, organic matter and concentration of Pb, Cd and Ni were determined in the sediment samples.

Results: The results showed a much sharper increase in electrical conductivity from station no.4 (Ejieh) to station no. 6 (Gavkhuni). Also, the sediment pH of Zayandeh Rud was alkaline with a minimum of 7.3 in station no. 2 (Chom) and a maximum of 7.9 in station no. 4. Concentration of Ni and content of organic matter increased from station no. 1 (Siosepol) to station no. 3 (Ziyar). The highest concentration of Pb was 72.1 mg/kg in station no. 2.

Conclusion: According to the results of this study, concentration of Pb in urban areas was higher than the downstream. Concentration of Cd was 2 mg/kg in station no. 5 and in another stations was very low. Therefore, the sediments of the river are not contaminated with cadmium.