Desorption of dissolved iron, manganese and zinc from sediment in an estuary

Abstract

We surveyed suspended solids (SS) and heavy metal ions, such as iron, manganese and zinc in sediments, in order to evaluate contribution of sediments to heavy metal ions in the estuary. We found that SS increased in the estuary during low tide and this fact was concluded to be due to resuspension of sediments by a large tidal difference. The sediment samples were equilibrated with seawater at several concentrations, which were diluted with water. As a result, iron concentration dissolved into the mixed seawater was negligibly low. This may be due to the fact that iron exists as an iron complex with humic substances, which is insoluble into the mixed seawater by the salting-out effect. While, the concentrations of manganese and zinc dissolved into the seawater were found to increase with increase in salinity in the seawater, which was in good accordance with the results that the fractions of manganese and zinc in the exchangeable form in the sediment samples were higher than that in the other samples.