Abstract:
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.
