Geochemical and Environmental Assessment of Some Minor and Trace Elements in Soils of Najaf Province, Southwest Iraq


125 Soil samples were collected from Najaf province which located within the southern deserts and Mesopotamia plain to determine the geogenic geochemical background range values for some chemical elements in the province. Some minor and trace elements (Al2O3, Fe2O3, SO3, Cu, Zn, U, Cr and Ni) were analyzed by Titration and Atomic Absorption Spectrophotometry (AAS) and chemical properties of soil such as PH and the presence of salt (TDS, SO3), are statistically treated in this study to extract natural background values for these terrains. Natural (geogenic) background range values are presented in two ways: the first involved all analytical results including natural anomalous values and the second after removing values above the statistically calculated threshold. The concentration range values for the studied area are comparable to those reported for world soil with some exceptions. Higher upper range values are noticed for Cr, but the median values are within the world range. The distribution of minor elements ( Al2O3, Fe2O3 and SO3) is largely controlled by parent rocks. Some trace elements are also related to source rocks, especially U, Cr and Ni. Sulfate is enriched by authigenic processes. This study clearly emphasizes the impact of various soil – forming processes, parent rocks, physiography and climate on the geogenic background range of the analysed elements. It also suggests that local environmental studies to demonstrate pollution cases should consider comparison with backgrounds of the uncontaminated soil related to the same physiographic terrain instead of making conclusions based on comparison with world averages for soil.