Regional-scale investigation of salt ions distribution characteristics in bauxite residue: A case study in a disposal area

Revegetation on bauxite residue disposal areas is the most promising strategy to reduce its potential ecological risk during stacking or disposing. Migration of salt ions in bauxite residue is one of the major issues to stimulate soil formation to support plant growth. 21 residue samples were collected and the related parameters including exchangeable cations, soluble ions, total salt, pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP) were selected to evaluate alkalization and salinization of bauxite residue. High levels of ions, cation exchange capacity (TOC), total salt, exchangeable sodium percentage (ESP) and cation exchange capacity (CEC) in bauxite residue were detected with greater coefficient of variation (CV), which indicated that distribution characteristics of salt ions varied significantly. The percentage of sulfate-chloride-soda type in the residues accounted for 71.43%. The mean value of pH was 10.10, whilst mean value of ESP was 52.05%. It indicated that the residues in this case study belonged to sulfate-chloride-soda saline and alkaline soil. The research results could provide theoretical basis for soil formation in bauxite residue.