107 J. Adv. Appl. Geol. Summer, 2019, No: 32 Investigating contamination and sources of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in surface sediment of Qarasoo River, Kermanshah Meisam Rastegari Mehr 1 , Adnan Deshaee 1 , Ata Shakeri 1 1-Assistant Professor in Environmental Geology, Faculty of Earth Sciences, Kharazmi University Keywords: Heavy metals, PAH, Qarasoo River, Sediment, Kermanshah 1-Introduction Land use change and entry of pollutants such as sewage sludge, mineral waste, industrial waste, pesticides and use of fertilizers are the main factors changing flood flow and contaminating river sediments with heavy metals and organic contaminants (Chen et al., 2004; Lepane and Heonsalu, 2007; Gautam et al., 2013; Amin et al., 2014; Singh et al., 2014; Narsimlu et al., 2015; Kumar et al., 2017). In general, sediments are the important indicators for contamination, by which the type and amount of contaminants could be identified, to help decision makers for better management. In developing countries such as Iran, ecological problems associated with heavy metals and organic compounds can be exacerbated by inappropriate management and poor standards. Most of the previous studies in Iran have investigated the pollution of large rivers such as Karoon and Zayandehrud (Keshavarzi et al., 2015; Rastegari Mehr et al., 2012), while less attention has been paid to smaller rivers such as Gharasoo in Kermanshah, despite numerous sources of industrial and urban pollution. Due to crossing the river from different land uses including agricultural, industrial and urban, the present study was conducted to assess heavy metals and polycyclic aromatic hydrocarbons (PAHs), and source identification for the first time in the Gharasoo River sediments which is located in the boundaries of the Kermanshah province. 2-Materials and Methods A total of 19 surface sediment sampled from different points, were analysed using ICP-MS and GC-MS methods after preparation to determine the concentration of selected heavy metals and 16 polycyclic aromatic hydrocarbons (PAHs), respectively. For analyzing the data (geochemically and statistically) contamination factor (CF), pollution load index (PLI), enrichment factor (EF), toxic equivalence index (TEF) and principal component analysis (PCA) were used (Hakanson, 1980; Tomlinson et al., 1980; Ergin et al., 1991; Nisbet and LaGoy, 1992; Cabrera et al., 1999; Sutherland, 2000; Blaser et al., 2000; Zhang and Liu, 2002; Sprovieri et al., 2007). 3-Results and discussion The texture of Qaraosoo River sediments were mainly sandy silt, silty loam, and sandy-silty-loam, indicating fine-grained texture. High concentrations of metals at the sediment surface indicate that the presence of one or more point source of contaminants may increase the concentration of these elements. The main contamination sources includes discharging various types of sewage, refinery waste and existing garbage in the river's margin. The differences in heavy metals concentrations between samples taken from urban areas and distant points from contaminating sources indicated the role of human activities on sediment quality. In general, the contamination factor in most stations is moderate or high, which indicates the relative pollution of the Qaraosoo River sediments. Also, the results of PLI calculation showed that in 47.36% of stations the values of this index are more than one. The lowest amount of PLI is related to Brimvand and Meymoon Baz stations, indicating the dominance of geogenic sources for elements in the upstream of the river. The results of the enrichment factor showed that all of the studied metals are more or less enriched in the sediments of the river compared with the average of shale. It seems that the elements in the first and second components in PCA have anthropogenic origins. The third component indicates the dominance of geogenic source for aluminium, which is due to the erosion and release of this element from the lithology of the upstream and the soil formation.  adnandeshaee@gmail.com