Chemical composition of ferromanganese nodules and surface layer pelagic bottom sediments from the Pacific Ocean

Results of an experimental study of ion exchange properties of Fe-Mn nodules and deep-sea pelagic host sediments are under consideration. The exchange complex of sediments and nodules includes Na+, K+, Ca2+, and Mg2+ cations. Fe-Mn nodules also include Mn2+ cations. Series of reactivity of metal cations during exchange reactions in different types of pelagic clayey sediments and diagenetic-sedimentary Fe-Mn nodules are compiled. Series of exchange capacity of the sediments and Fe-Mn nodules for alkali and heavy metal cations are also presented. Exchange capacity of the Fe-Mn nodules is always higher than that of the host sediments. The host sediments are characterized by reversible equivalent sorption of cations of both alkali and heavy metals. Irrespective of mineral composition, the Fe-Mn nodules are characterized by reversible equivalent sorption of alkali metal cations, whereas sorption of heavy metal cations is only partly reversible. More over, alkali metal cations do not replace heavy metal cations. The results obtained specify the role of ion exchange processes in redistribution of heavy metal cations at the water - bottom sediment interface during diagenetic-sedimentary formation of Fe-Mn nodules.