Deciphering Vanadium Speciation in Smelting Ash and Adaptive Responses of Soil Microorganisms

Abstract

Abundant smelting ash is discharged during pyrometallurgical vanadium (V) production. However, its associated V speciation and resultant ecological impact have remained elusive. In this study, V speciation in smelting ash and its influence on the metabolism of soil microorganisms were investigated. Smelting ashes from V smelters contained abundant V (19.6-115.9 mg/g). V(V) was the dominant species for soluble V, while solid V primarily existed in bioavailable forms. Previously unrevealed V nanoparticles (V-NPs) were prevalently detected, with a peak concentration of 1.3 × 10¹³ particles/g, a minimal size of 136.0 ± 0.6 nm, and primary constituents comprising FeVO₄, VO₂, and V₂O₅. Incubation experiments implied that smelting ash reshaped the soil microbial community. Metagenomic binning, gene transcription, and component quantification revealed that <i>Microbacterium</i> sp. and <i>Tabrizicola</i> sp. secreted extracellular polymeric substances through <i>epsB</i> and <i>yhxB</i> gene regulation for V-NPs aggregation to alleviate toxicity under aerobic operations. The V K-edge X-ray absorption near-edge structure (XANES) spectra suggested that VO₂ NPs were oxidized to V₂O₅ NPs. In the anaerobic case, <i>Comamonas</i> sp. and <i>Achromobacter</i> sp. reduced V(V) to V(IV) for detoxification regulated by the <i>napA</i> gene. This study provides a deep understanding of the V speciation in smelting ash and microbial responses, inspiring promising bioremediation strategies to reduce its negative environmental impacts.