Heavy Metals Contamination in Soil, Surface Water and Groundwater of an Agricultural Area Adjacent to Tehran oil Refinery, Iran

Concentrations of six heavy metals including Cr, Mn, Ni, Pb, V and Zn were determined in top soil (from 47 grid cells), surface water (4 streams) and groundwater (8 wells and 4 qanats) from an agricultural area located at south part of the Iranian capital, near the Tehran oil refinery. Concentrations of the elements were measured using flame and flameless atomic absorption spectrometry. Based on the results of agglomerative hierarchical method for clustering of the soil grid cells, some similarities between the dendrograms of Mn and Ni, Pb and V, and Zn and Cr were observed. The pattern of metal occurrence exhibited the following descending order: Mn > Zn > Cr > V > Ni > Pb for soil, Pb, Ni, Mn > Zn, V, Cr for wells and Ni, Pb > Cr, V > Mn, Zn for streams. Significant positive correlations were found among Zn, Cr and Ni as well as between Mn and Zn, Ni and V, and Pb and Zn in soil. Significant positive associations were also observed in the case of Mn-Ni and MnCr in wells and streams, respectively. The mean concentrations of the heavy metals in the soil exceeded the normal uncontaminated soils (with the exception of V). In the case of Cr, Zn and V, our results were above the soil critical range. The mean levels of all the elements in the surface and groundwater were considerably lower than the related guidelines and limits.