Chenglong Lu paper accepted by Chemical Geology
Chenglong Lu and coauthors reveal how mineral phase transformation drives DOM molecular fractionation during organic acid-driven weathering of bauxite residue.
Authors: C Lu, S Wu, F You, D Yu, J Vongsvivut, A Klein, L Thomsen, D Parry, TS Chan, L Huang
Journal: Chemical Geology, 2026
Dissolved organic matter sequestration is critical to soil formation of bauxite residue, where mineral weathering and neutralization or acidification are driven by microbial- and plant root-derived organic acids. This study used mixed organic acids to simulate mineral weathering during ecological engineering and examined DOM molecular fractionation and adsorption in bauxite residue minerals.
Using high-resolution electrospray ionization Orbitrap mass spectrometry, the study characterized selective adsorption and molecular fractionation of DOM derived from microbial decomposition of plant mulch. Organic acid treatments progressively weathered sodalite-like alkaline minerals, formed amorphous Al/Si/Fe phases, lowered pH, and increased reactive surface sites.
Slightly and highly weathered bauxite residue minerals preferentially adsorbed high-molecular-weight organics rich in aromatic and/or polyphenolic domains. Synchrotron-based Al, Si, and Fe K-edge X-ray absorption spectroscopy and FTIR mapping further revealed strong associations between secondary Al/Si/Fe phases and protein-, carboxylic-, aromatic-, and oxygenated lipid-like compounds.