A Comparative Study of Total and Bioavailable Cadmium and Zinc Concentrations and Distributions among Different Land Use Types within Baghdad City

Abstract

Total and bioavailable levels of Cd and Zn in topsoil (0–20) cm taken from four different land use types (residential, commercial, industrial and mixed) of the urban area of Bagdad, Iraq, were analyzed by the flame atomic absorption spectrophotometer. This was with a view to appraising the influence of a variety of anthropogenic activities on heavy metal contamination of the urban soil. Results showed that the range of Cd and Zn were (0.00-6.35) mg/kg and (5.20-219.95) mg/kg respectively. As compared with the calculated world average of unpolluted soils, cadmium displays higher concentrations while the zinc concentration was within this common world range. The level of pollution was assessed using geoaccumulation index (Igeo), for all land use types Igeo decreasing order, followed the order of (Cd> Zn). The relative bioavailability for Cd, and Zn has been observed as 2.46-5 % and 2.80-9.78 % respectively. It can be concluded that, although total concentrations of the examined heavy metals were generally high, but at the same time the bioavailable ones were relatively low. This can be an indicator that with the recent environmental factors (alkaline to sub-alkaline soil pH), the toxicity of heavy metals to humans was in its minimum level.