GEOCHEMICAL PARTITIONING OF HEAVY METALS IN THE URBAN SOIL, KIRKUK, IRAQ
This work focused on anthropogenic influences of the trace metals distribution in the soils of Kirkuk city. Sequential extraction technique was used to determine the distribution of the chemical fractions of Ag, Cd, Co, Cu, Ni, Pb, Zn, As, Cr and V in soil of Kirkuk city. This area is affected mainly by burning oil trash. Results show that these heavy metals were primarily restricted to surface horizons and mostly associated with the residual fraction (28.8 – 50%). The remnant fractions (13.8 – 33.1%) linked to the organic matter, 7.9 – 27.2% was bound to Fe-Mn oxide, 0.7 – 27.9 was bound to carbonate. Only a small amount of the total metals in the soil is exchangeable (0.5 – 4.2%) and water soluble (0 – 4.1%) fractions. Ag, Cd, Cu, As, Cr and V mainly associated to organic matter fraction; Co, Ni and Zn mostly bound to Fe-Mn oxide fraction; Pb primarily bound to the carbonate fraction. Metals that are bound to the organic matter fraction could be released under oxic conditions, while those associated with Fe-Mn oxide and carbonate fraction could be leached out by changes in the ionic composition and pH. The mobility factors for the metals in the surface soil ranged from 0 to 36 for Ag, 22.2 to 43.6 for Cd, 5.3 to 20.8 for Ni, 16.1 to 41.2 for Pb, 7.3 to 37.9 for Zn, 10.4 to 22.9 for As, 3.2 to 12.3 for Cr and 2.4 to 9.4 for V. The high level of metals remnant as residual fraction coupled with low values of mobility factors, indicate that these metals do not cause any environmental risk or hazard.