natural pollution by some heavy metals in the tigris river, northern iraq

twenty samples of the recent sediments were collected from the tigris river and some of its tributaries of northern iraq and twelve samples from the miocene and quaternary sediments. the study is conducted to define and assess the paleoenvironmental pollution by some heavy metals in these sediments in order to elucidate the probable source rocks and the main mineral phases suggested to be a source of such pollution by using x-ray diffraction, x-ray fluorescence and scanning electron microscopes analyses. the study indicates a polluted level of some heavy metals mainly cr, cu, ni, pb and zn. clay and heavy minerals may form the main sources for this natural pollution. the combined affects of mechanical attrition and chemical etching during the transportation by the river water are indicated through several morphological characteristics on the surface textures of the heavy minerals. the high concentration of some of the studied trace elements could be attributed to incorporation of such elements in the lattice of the heavy and clay minerals.