Settling particles in the Golden Horn estuary, Sea of Marmara: Concentrations and fluxes of trace elements and radionuclides

The Golden Horn estuary, which is located along the Sea of Marmara adjacent to the center of Istanbul, has been heavily polluted for centuries due to concentrated shipping activities, and a legacy of industrial and municipal discharges. The municipalities and associated governments have implemented environmental rehabilitation projects for over 25 years. However, the Golden Horn estuary is still exposed to various pollutants such as vehicle emissions including from fossil-fuel combustion. In this study, two sediment traps were deployed in the Golden Horn estuary to obtain information on settling particle (SP) composition and fluxes, trace element and radionuclide concentrations, and fluxes thereof. Conventional sediment traps (Trap-1 and Trap-2) were installed side-by-side, at a depth of 15-m and moored for 18 months during which time the sediment traps were periodically sampled. Over this time period, settling particle fluxes (SPFs) were calculated. The concentrations and fluxes of radionuclides (Cs-137, Ra-226, Ra-228, Po-210, and Pb-210) and trace elements (Ag, Al, As, Cd, Cu, Fe, K, Mn, Mo, Ni, Pb, Sb Sn, Tl, V, and Zn) were determined in SPs for each sampling period. Normalized enrichment factors (EF) and a Geoaccumulation Index (I-geo) showed that Ag, Cd, and Pb were statistically enriched in SPs. Together, the results of this study show that the Golden Horn estuary is still enriched in some environmental pollutants which could be a source term for the water column and associated marine animals. (C) 2021 Elsevier B.V. All rights reserved.