Uptake and accumulation of heavy metals by water body and Azolla filiculoides in the Anzali wetland

The Anzali international wetland is a valuable habitat to a wide variety of aquatic flora and fauna. This wetland ecosystem is being threatened due to various pollutants particularly the heavy metals discharging from different point and non-point sources. Concentration of various heavy metals (Cr, Pb, Hg, Cu, Zn, Cd, Ag and Ti) was examined in the water body and Azolla filiculoides (an exotic fern in the Anzali wetland). The samples regarding water and A. filiculoides were randomly carried out in three parts of the wetland (eastern, central and western parts) in May 2015. After preparing and digesting the samples, the concentration of the heavy metals was measured using ICP OES method. The obtained results showed that the concentration of Zn in water and A. filiculoides samples was higher than other heavy meals in all parts of the wetland (p < 0.05). Overall, concentration of the heavy metals was significantly higher in the eastern part of the wetland than other two sampling locations (p < 0.05). Also with comparing the concentration of the heavy metals in water and A. filiculoides, it was found that all examined metals (except Cd and Ag) in A. filiculoides had significantly higher concentration than water sample, while Cd and Ag in water and A. filiculoides did not have a significant difference with each other. Based on the results, it can be concluded that A. filiculoides can effectively absorb Cr, Pb, Zn, Hg, Cu, Cd, Ag and Ti so that it might be used as a valuable species for the bioremediation and the removal of heavy metals from the wetland.