Effect of Redox Potential on Changing of Binding Forms of Heavy Metals in Bottom Sediments of Anzali International Wetland

Heavy metals are naturally presented in different chemical bonds within sediment. Different factors affect metals bonding in sediment. One of those factors is changing in Redox potential. Redox potential may change under oxic/anoxic conditions in the bottom sediments.
In the present study the effect of redox potential on fractionation and bonding of metals within Anzali international wetland bottom sediment is investigated.
Findings: Sediment samples of Anzali wetland were aerated for one month and redox potential and pH was measured at 0, 1, 7, 21, and 28th days. Subsamples of sediments at mentioned days of experiments were taken and analyzed for Cu, Zn, Ni, and Cr for deferent chemical bonds using sequential extraction analysis.
Discussion and Results revealed that majority of Cu were presented in the sulfidic/organic bonds while Zn was associated with Fe/Mn oxides. Nickel and Cr were mostly associated in hard residual bonds. At the end of aeration process, with increasing redox potential, 8-23% of metals were released from sediments into dissolved phase. They mainly released from sulfide/organic bonds.