SEASONAL VARIATION AND ASSESSMENT OF HEAVY METALS POLLUTION IN SEDIMENTS FROM SELECTED STATIONS IN TIGRIS AND EUPHRATES RIVERS, CENTRAL IRAQ

In this study, four sampling stations were selected from two locates on the Tigris river (Baghdad region) and others on the Euphrates river (Al-Anbar Governorate) in order to determine concentrations, seasonal variation and pollution intensity assessment of heavy metals (Ni, Cu, Pb, Mn and Cd) in the two rivers sediments. Distribution of studied metals showed that stations in the Tigris river generally had higher concentrations than stations in Euphrates river. Manganese was found at high concentrations in all studied stations and ranged between 200 - 500 ppm, while Cd was found at the lowest concentrations and ranged between not detected to 1.8 ppm during study period. Based on index of geoaccumulation (I-geo) for studied heavy metals indicates that the surface sediments in the studied stations are unpolluted by Ni and Mn, while unpolluted to slightly polluted by Pb and Cd except the Cd at south of Baghdad station (moderately polluted). The I-geo for Cu indicate the sediments were unpolluted to slightly polluted in the Tigris stations, and unpolluted in the Euphrates stations. The calculated enrichment factor (EF) indicate that all stations can be classified as minimal enrichment for Ni, moderate enrichment for Cu and significant enrichment for the elements Pb and Cd.