Nitrogen-Rich Organic Matter Formation and Stabilization in Iron Ore Tailings: A Submicrometer Investigation
Songlin Wu, Jeremy Bougoure, Jian Wang, Lars Thomsen, Ting‐Shan Chan, Qing Yi, Zhen Li, Gordon Southam, Longbin Huang
Abstract
Organic matter (OM) formation and stabilization are critical processes in the eco-engineered pedogenesis of Fe ore tailings, but the underlying mechanisms are unclear. The present 12 month microcosm study has adopted nanoscale secondary ion mass spectrometry (NanoSIMS) and synchrotron-based scanning transmission X-ray microscopy (STXM) techniques to investigate OM formation, molecular signature, and stabilization in tailings at micro- and nanometer scales. In this system, microbial processing of exogenous isotopically labeled OM demonstrated that 13 C labeled glucose and 13 C/ 15 N labeled plant biomass were decomposed, regenerated, and associated with Fe-rich minerals in a heterogeneous pattern in tailings. Particularly, when tailings were amended with plant biomass, the 15 N-rich microbially derived OM was generated and bound to minerals to form an internal organo-mineral association, facilitating further OM stabilization. The organo-mineral associations were primarily underpinned by interactions of carboxyl, amide, aromatic, and/or aliphatic groups with weathered mineral products derived from biotite-like minerals in fresh tailings (i.e., with Fe 2+ and Fe 3+ ) or with Fe 3+ oxyhydroxides in aged tailings. The study revealed microbial OM generation and subsequent organo-mineral association in Fe ore tailings at the submicrometer scale during early stages of eco-engineered pedogenesis, providing a basis for the development of microbial based technologies toward tailings’ ecological rehabilitation.