چكيده به لاتين
Discharging multiple effluents from petrochemical industries exposes the water body of Musa estuary to redox potential changes. In this study, the effect of redox potential on the release dynamics of metals and changes in the distribution of metals onto binding phases within the sediments have been investigated. Furthermore, the releasing bindings of these metals have been identified. A surface sediment sample had already been collected using a Van Veen Grab sampler in May 2017. The redox potential adjustments were performed by an automated biogeochemical microcosm system. The redox potential first decreased from the initial value (120 mV) to 50 mV and then to -150 mV. At each step, sampling was carried out for the measurement of heavy metals. Sediment was subjected to the total extraction and Tessier sequential extraction procedure. The concentrations of metals in water and sediment were determined by inductively coupled plasma spectroscopy. The results showed by decreasing the redox potential to 50 mV, the soluble concentration of all metals increased except for Cd. Subsequently, the soluble concentration of As, Cr, Cu, Ni, and Zn decreased as the redox potential decreased to -150 mV. While the soluble concentration of Co and V was constant and the soluble concentration of Pb increased. By decreasing the redox potential, Cd, Co, and Zn transformed from the weak to strong bindings and the soluble Cd adsorbed to the residual phase. Also, all the phases with exception of the residual were involved in the release of Co and Zn. The exchangeable, carbonate, and organic-sulfidic phases of Cu were transferred to Fe-Mn oxides and residual phases, and also these phases played the most role in the release of Cu. The exchangeable, carbonate, and Fe-Mn oxides phases of Ni were transferred to the residual phase, and also the mentioned phases played the most role in the release of Ni. All phases, except the organic-sulfidic phase, contributed to the release of Pb. In this way, the impact of redox potential on the sudden release of metals from sediments has specified, as well as risk assessment and fate examining of these metals, along with other information that will enable planning and sustainable management.