Comparative assessment of baseline concentration of the heavy metals in the soils of Tehran (Iran) with the comprisable reference data

Industrial soil systems have become complex due to human activities, as they disturb the natural development of soil and add hazardous elements. Hence, there is a growing public concern over the accumulation of heavy metals in soil due to the rapid industrial development during the last decade in Iran. The objectives of the present study are to carry out comparative assessment of the heavy metals in soils of the Chitgar Industrial Area Tehran (Iran) with average world guidelines and to evaluate enrichment and normalized scatter coefficient. In this work the concentrations of seven heavy metals (Cr, Co, Cd, Cu, Pb, Ni and Zn) from the surface soils of the industrial area were quantified, based on 210 samples collected from 70 sampling stations in three consecutive seasons May 2007, November 2007 and May 2008 using 0.5 × l Km square mesh. Common comparison methods were employed to assess the quality of soils and guideline values were used to represent a desired level of elements. Comparison variables and enrichment factor showed that Pb has high-level value while normalized scatter coefficient demonstrates that Cd increases in soils more rapidly as compared to other elements. This study revealed that normalized scatter coefficient can be effectively used to evaluate soil pollution and is independent of the past.