H eavy metal contamination and risk assessment in the riverine sediment

Intensity of pollution was evaluated using enrichment factor (EF), geo-accumulation index (Igeo), pollution index (IPOLL), m – ERM – Q and RF for (As, Cd, Cu, Mn, Ni, Pb and Zn) in sediments collected from Siahrud river, Iran. Chemical sequential extractions were employed for determination of the anthropogenic portions of metals. Heavy metal contents in the sediments follow the order of Al>Ca>Mn> Zn > Ni > Cu >Pb> As > Cd. Anthropogenic portion of the metals was determined through three-step chemical sequential extraction. The results of partition studies revealed the proportion of anthropogenic metals to their original bulk concentrations are Pb(85%) > Zn(84%) > Cd( 62%) > As(47%) >Mn(35%) > Ni(34%) > Cu(2l %). Mean enrichment factor (EF) values obtained for various metals were between moderate enrichment and extremely high enrichment. Based on the classification of metals contamination, all sediment samples have a 74% probability of toxicity. Newly developed pollution index (RF) showes very good perfomance to determine the degree of contamination. Interestingly, the results of chemical partitioning tallies well with cluster analysis. Metals with highest anthropogenic portions are grouped together at a high similarity coefficient. Presence of organic matter in this group may be indicative of organic pollution source.