Dynamic change and diagnosis of physical, chemical and biological properties in bauxite residue disposal areas

Abstract

Vegetation encroachment occurred in bauxite residue disposal area (BRDA) following natural weathering processes, whilst the typical indicators of soil formation are still uncertain. Residue samples were collected from the BRDA in Central China, and related physical, chemical and biological indicators of bauxite residue with different storage years were determined. The indicators of soil formation in bauxite residue were selected using principal component analysis, factor analysis, and comprehensive evaluation to establish soil quality diagnostic index model on disposal areas. Following natural weathering processes, the texture of bauxite residue changed from silty loam to sandy loam. The pH and EC decreased, whilst porosity, nutrient element content and microbial biomass increased. The identified minimum data set (MDS) included available phosphorus (AP), moisture content (MC), C/N, sand content, total nitrogen (TN), microbial biomass carbon (MBC), and pH. The soil quality index of bauxite residue increased, and the relative soil quality index decreased from 1.89 to 0.15, which indicated that natural weathering had a significant effect on improveing the quality of bauxite residue and forming a new soil-like matrix. The diagnostic model of bauxite residue was established to provide data support for the regeneration on disposal area.