Heavy metal content and distribution in surface sediments of Lower Seyhan River

In this study, chemical fractionation of six heavy metals ( Cr, Cu, Mn, Ni, Pb and Zn) was studied using a modified three- step sequential procedure to assess their impacts in the sediments of the Seyhan River. Samples were collected from six representative stations in two campaigns in October 2010 and June 2011. The total metal concentrations in the sediments demonstrated different distribution patterns at the various stations. Metal fractionation showed that, except for Mn and Pb, the majority of metals were found in the residual fraction regardless of sampling time, indicating that these metals were strongly bound to the sediments. The potential mobility of the metals (non-residual fractions) is reflected in the following ranking: Mn>Zn>Ni>Pb>Cu>Cr in October 2010 Mn>Zn>Ni>Pb>Cr>Cu in June 2011. The second highest proportion of metals was bound to organic matter/ sulfides, originating primarily from anthropogenic activities. Non-residual metal fractions for all stations were highest in June 2011, which may be linked to higher organic matter concentrations in sediment. Potential sediment toxicity was evaluated using the Risk Assessment Code (RAC). Based on RAC classification, Cr pose no risk, Cu and Ni pose low risk, Pb and Zn were classified as medium risk metals, while the environmental risk from Mn was high. In addition, based on the sediment quality guidelines (SQG), the Seyhan River can be classified as a river with no, to moderate, toxicological risks, based on total metal concentrations