Factors Affecting the Levels of Toxic Metals in the Shatt Al-Arab River, Southern Iraq

Abstract

During the last two decades, the changes in the economic setting of the Basra province and the hydrological system of the Shatt Al-Arab River have led to significant shifts in the sources and levels of contaminants in the river. Therefore, the levels of toxic metals (Ni, Cr, Pb, As, Hg, U, and Cd) in the surface water and bed sediments at four sites have been measured to investigate the natural and anthropogenic influences that have led to these shifts. In comparison with the sediments, low concentrations and a uniform distribution of most metals were observed in the river water. The results show that the river sediments were polluted with toxic metals, while pollution levels in the water are still within permissible limits for drinking, irrigation, and aquatic life. These findings indicated that the major sources of river contamination with toxic metals are the atmospheric deposit of gaseous emissions from oil production and electric generators and the surface runoff from agricultural areas after rainfall. In addition, the tide greatly controls the distribution toxic metals in the river. In addition, the physicochemical properties of the water and sediments play an important role in the metal accumulation, while the effect of agricultural, industrial, and domestic sewage is limited. However, the water quality in the Shatt Al-Arab River reflects the combined effects of natural and anthropogenic factors.