Molecular insights into the chemodiversity of dissolved organic matter and its interactions with the microbial community in eco-engineered bauxite residue.

Dissolved organic matter (DOM) plays an important role in the biogeochemical function development of bauxite residue. Nevertheless, the DOM composition at the molecular level and its interaction with microbial community during soil formation of bauxite residue driven by eco-engineering strategies are still relatively unknown. In the present study, the DOM composition at the molecular level and its interactions with the microbial community in amended and revegetated bauxite residue were explored. The results showed that the amendment applications and revegetation enhanced the accumulation of unsaturated molecules with high values of double bond equivalent (DBE) and nominal oxidation of carbon (NOSC) and aromatic compounds with high values of modified aromaticity index (AI) as well as the reduction of average weighted molecular mass of DOM molecules. Significant correlations between DOM molecules and the microbial community and Fe/Al oxides were found. DOM molecules were decomposed by the microbial community and sequestered onto Fe/Al oxides, which were the main driving factors that changed DOM chemodiversity in the amended and revegetated bauxite residue. These findings are beneficial for understanding the biogeochemical behaviours of DOM and providing a critical basis for the development of eco-engineering strategies towards soil formation and the sustainable revegetation of bauxite residue.