Contents lists available at ScienceDirect Ecological Indicators journal homepage: www.elsevier.com/locate/ecolind Potential toxic elements in sediment of some rivers at Giresun, Northeast Turkey: A preliminary assessment for ecotoxicological status and health risk Fikret Ustaoğlu a , Md. Saiful Islam b,c, ⁎ a Biology Department, Faculty of Arts and Science Giresun University Gure Campus, 28200 Giresun, Turkey b Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali 8602, Bangladesh c Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan ARTICLE INFO Keywords: Risk assessment Health hazard index Trace metals Multivariate statistical analysis River Sediments Turkey ABSTRACT The concentration of globally alarming potential toxic elements (PTEs) like Aluminum (Al), chrome (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), lead (Pb), and uranium (U) were measured in surface sediment of seven major rivers residing in Giresun (one of the most important Hazelnut production areas of Turkey). The mean concentrations of PTEs in all river sediments showed the descending order of Al > Fe > Mn > Zn > Cu > Pb > Cr > Ni > Co > As > U > Cd. The level of studied metals in most of the rivers exceeded the threshold effect level (TEL), indicating a potential risk to the environment. Certain indices, including the sediment quality guidelines (SQGs), contamination factor (CF), pollution load index (PLI), enrichment factor (EF), potential ecological risk index (E r i ), geoaccumulation index (I geo ), toxic risk index (TRI), modified hazard quotient (mHQ) and ecological contamination index (ECI) were used to assess the ecological risk posed by PTEs in sediment. Contamination factor (CF) and geoaccumu- lation index (I geo ) demonstrated that most of the sediment samples were moderately to considerably con- taminated by Cu, As, Cd and Pb. In view of the potential ecological risk index, sediments from Pazarsuyu Stream (PS), Batlama Stream (BS) and Gelevera Stream (GLS) showed considerable potential ecological risk. The sources of PTEs and the relations between them were determined by using principal component analysis/factor analysis (PCA/FA), Hierarchical clustering analysis (HCA) and Pearson correlation index (PCI). Three factors explaining 83.94% of the total variance was found by PCA/FA. 43.34% of the total variance explained by the first factor (F1) was correlated with Ni, Cr, Pb and Co elements. 28.35% of the total variance explained by the second factor (F2) was correlated with U, Al, the third factor (F3) explains 12.24% of the total variance and correlated with Zn, Cd, Cu and As elements. These factors revealed that the quality of the sediment was mainly influenced by anthropogenic effects. The extent of pollution by heavy metals in the studied streams implies that the condition is much frightening to the biota and inhabitants in the vicinity of these rivers as well. 1. Introduction Potential Toxic Elements (PTEs) are non-biodegradable, toxic to all living organisms and have significant health-related side effects (Kükrer et al., 2015; Yalçin Tepe, 2013). In recent years, due to the rapid ex- pansion of emissions sources, they pose serious threat to the aquatic ecosystems (Chau, 2005; Türkmen et al., 2011). However, the spread of PTEs to the environment occur commonly through geological weath- ering, volcanoes, erosion, exhaust gases of motor vehicles, mining sites, metal-containing fertilizers, pesticides, runoff and various urban and industrial activities (Islam et al., 2015, 2018; Tokatlı et al., 2015). Besides, continuous accumulation of contaminants in the environment severely deteriorates the quality of environment and adversely affects the structure of biosphere, causing changes in the normal biogeo- chemical cycle (Alizadeh et al., 2017, 2018; Maria Cavadas Morais Couto et al., 2019). Therefore, the distribution, potential ecological risks and emission sources of PTEs is crucial for effective environmental risk management (Tepe et al., 2017; Kormoker et al., 2019). In rivers stream, estuaries and bays, water quality is a critical issue due to the high potential for anthropogenic pollution in runoff (Shamshirband et al., 2019). In the hydrological cycle, the chemical composition and quality of water-related sediments are highly influenced by the elevated concentration of pollutants (Taş et al., 2019). However, sediment is an important part of the environment that provides the necessary en- vironmental information and regarded as the final precipitating medium for PTEs (Chen and Chau, 2016, 2019; Fiket et al., 2019). As https://doi.org/10.1016/j.ecolind.2020.106237 Received 20 December 2019; Received in revised form 9 February 2020; Accepted 19 February 2020 ⁎ Corresponding author at: Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali 8602, Bangladesh. E-mail address: msaifulpstu@yahoo.com (Md. S. Islam). Ecological Indicators 113 (2020) 106237 1470-160X/ © 2020 Elsevier Ltd. All rights reserved. T