Assessing the trace metal pollution in the sediments of Mahshahr Bay, Persian Gulf, via a novel pollution index A. R. Vaezi & A. R. Karbassi & M. Fakhraee Received: 20 May 2015 /Accepted: 26 August 2015 # Springer International Publishing Switzerland 2015 Abstract Sediment samples were collected from the Petrochemical Special Economic Zone of Mahshahr Bay, Persian Gulf, and analyzed for possible trace metal contamination by means of a chemical partitioning method. The heavy metal contents in the sediments follow the order of Al>Sr>Mn>Zn>Ni>Ba>Cr> Cu>As>Co. The degree of sediment contamination was evaluated using pollution load index (PLI), modi- fied degree of contamination (mC d ), geo-accumulation index (I geo ), and enrichment factor (EF). All these indi- ces compare present concentrations of metals to their background levels in crust and shale. In a specific area with high geological background like Mahshahr Bay, such a comparison may lead to erroneous conclusions. Due to the remarkable contribution of lithogenous frac- tion, as the natural component, to the bulk concentration of trace metals in the sediments of such an area, assessment of chemical hazard to the surrounding aquat- ic environment should not be carried out through tradi- tional approaches. In the present study, anthropogenic portion of the metals was determined through one-step chemical sequential extraction and lithogenous portion substituted for the mean crust and shale levels in the new pollution index (RI Aquatic ). PLI, mC d , and I geo revealed overall low values, but EF, pollution index (I POLL ), and newly developed pollution index were relatively high for all samples. Keywords Persian Gulf . Sediment contamination . Pollution index . Chemical partitioning . Anthropogenic portion Introduction Heavy metals are considered as a common environmen- tal contamination and a worldwide concern (Ergin et al. 1991; Sinem Atgin et al. 2000; Samani et al. 2014; Vaezi et al. 2014). Accumulation of trace metals in an aquatic system and sediments depends on different factors in- cluding the nature of sediment particles and factors affecting physicochemical conditions (Nemr et al. 2007; Tam and Wong 2000). Due to heavy metal toxic- ity, hard biodegradation, and easy bioaccumulation in aquatic ecosystems, various indices have been devel- oped (Yang et al. 2012) including sediment quality guidelines (SQGs) (Macdonald et al. 1996; Sundaray et al. 2011), enrichment factor (EF) (Tang et al. 2010), pollution load index (I POLL ) (Karbassi et al. 2008), and Environ Monit Assess (2015) 187:613 DOI 10.1007/s10661-015-4833-7 A. R. Vaezi : A. R. Karbassi Graduate Faculty of Environment, University of Tehran, 1417853111#23, Azin Avenue, Ghods Street, Enghelab Square, Tehran, Iran e-mail: Al.vaezi@ut.ac.ir A. R. Vaezi e-mail: Al.vaezi@yahoo.com e-mail: Akarbasi@ut.ac.ir A. R. Karbassi e-mail: Arkabssi738@yahoo.com M. Fakhraee (*) University of Minnesota, 173 McNeal Hall, 1985 Buford Ave., St. Paul, MN 55108, USA e-mail: fakhr008@umn.edu