Investigation of Contaminated Sediments by Toxic Elements Using Principal Component Analysis and Determination of Pollution Index in South East of Tehran

In this study the environmental problems has been studied in south east of Tehran (Bibi Shahrbanou mount). 31 sediment samples were taken from 10-15 cm extremity of streams and were analyzed by ICP. Toxic elements studied include: Ag, As, Cd, Cr, Cu, Ni, Pb, Sb and Zn. The samples were also investigated for mineralogy using XRD. The clay mineral assemblage encountered in the analyzed samples is composed of kaolinite, illite, montmorillonite, dictite, vermiculite, clinochlore. The nonclay minerals are composed mainly of quartz, calcite and dolomite as major minerals with alebite and muscovite as minor minerals. According to the index of geoaccumulation, the sediments of the study area are considered to be extremely polluted with respect to Sb and Ag, strongly polluted with respect to As, Cd, Zn and Cu, extremely to strongly polluted with respect to Pb, moderately to strongly polluted with respect to Cr, unpolluted to moderately polluted with respect to Ni. Except of As and Cr all the toxic elements are positively correlated with the determined physicochemical parameter such as pH, clay content, organic matter content, and carbonate content. Applied principal components analysis on the data makes nine principal components for the data set, the first three components of over 70 percent of the population variability to explain. The first component including Ag, Pb, Zn and Cu. Seems to be the first component in combination with abandoned lead mine and clay content. The second one including Ni and Sb, seems to be affected by organic matter and cation exchange capacity while the third including As and Cr is affected by cement factory. The results of cluster analysis are also fully consistent with the results of principal component analysis.