Strontium and vanadium sorption by iron-manganese nodules from natural and remediated Dystric Cambisols

Purpose This study aimed to investigate the concentration levels, vertical distribution, accumulation, and association of various forms of strontium (Sr) and vanadium (V) with reactive phase carriers in Dystric Cambisols in natural soil-forming environments and dumpsite areas remediated over a period of 13 to 16 years. Materials and methods Soil matrices and Fe–Mn nodules (sized 2–4 mm) were collected from different sites on the west coast of the Pacific Ocean and studied using advanced analytical methods and noninvasive techniques. Results and discussion The content and distribution of the macro-elements, Sr and V, in the soil matrix of control sites corresponded to those in natural landscapes of the regions under study. Strontium and V were mainly bound in stable soil compounds, with contents and distributions depending largely on the contents of clay and Al, Si, and Fe oxides. Compared to control sites, significant increases in Sr, V, organic-, Mn-, Ca-, Al- and Fe-bearing compounds, and alkalization of the soil solution were observed in dumpsite soils, accompanied by an increase in associations of Sr and V with these compounds and an increase in the proportion of extractable Sr and V forms in the soil matrix. Nodules acted as an accumulator and stabilizer of Sr and V in the soils across all sites studied. Enrichment factor assessment revealed a dependence between accumulation levels of Sr and V in nodules and the content of extractable forms, as well as various compounds containing Sr and V in the soil matrices. Conclusions Iron-Mn nodules from all studied sites act as geochemical barriers, effectively sequestering Sr and V ions and transferring them into more stable forms.