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

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.本文对铁锰结核（Fe-Mn nodules）与深海远洋宿主沉积物的离子交换特性实验研究结果进行了系统分析。沉积物与结核的离子交换复合体包含钠离子（Na+）、钾离子（K+）、钙离子（Ca²+）及镁离子（Mg²+）等阳离子；铁锰结核额外含有锰离子（Mn²+）阳离子。研究梳理得到不同类型远洋黏土沉积物与成岩-沉积型铁锰结核中，金属阳离子在离子交换反应中的反应活性序列；同时还给出了沉积物与铁锰结核针对碱金属及重金属阳离子的离子交换容量序列。铁锰结核的离子交换容量始终高于其宿主沉积物。宿主沉积物的典型特征为可对碱金属与重金属阳离子实现可逆等价吸附。无论矿物组成如何，铁锰结核仅可对碱金属阳离子实现可逆等价吸附，而对重金属阳离子的吸附仅能实现部分可逆。此外，碱金属阳离子无法置换重金属阳离子。本研究所得结果明确了离子交换过程在铁锰结核成岩-沉积形成阶段，水-沉积物界面处重金属阳离子再分配过程中所发挥的作用。