Sediment quality of Ergene River Basin: bio-ecological risk assessment of toxic metals.

Ergene River Basin is located in the north-west part of Marmara Region of Turkey. There are many industrial enterprises on its basin and as well as the majority of these facilities are located on the upstream of the basin. Therefore, Ergene River is one of the rare river ecosystems that are contaminated almost from the source area.The aim of this investigation was to assess the sediment contamination of Ergene River Basin including Meriç and Ergene Rivers and 10 significant tributaries of the system by investigating total of 25 macro- and micro-element concentrations. Sediments were sampled in spring season (rainy) of 2018 from 21 stations and element accumulations were investigated by using an ICP-MS.The investigated macro- and micro-elements in terms of concentration levels in abiotic components of the basin and the investigated basin components in terms of sediment quality characteristics were classified by using cluster analysis (CA). Biological Risk Index (mERM-Q) and Potential Ecological Risk Index (RI) were also applied to detected data to make an assessment of biological and ecological risks of toxic elements on the system.As a result of elemental CA, four statistically significant clusters were formed, which were named as "most intense elements", "moderate intense elements", "moderate rare elements", and "rarest elements". As a result of locational CA, three statistically significant clusters were formed, which were named as "low contaminated zone", "moderate contaminated zone", and "high contaminated zone". As a result of mERM-Q, chromium was determined as the most risky element, and as a result of RI, cadmium was determined as the most risky element for the sediments of Ergene River Basin.