Tracing the Biotransformation of Polycyclic Aromatic Hydrocarbons in Contaminated Soil Using Stable Isotope-Assisted Metabolomics

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Abstract
Biotransformation of organic pollutants may result in the formation of oxidation products that are more toxic than the parent contaminants. However, tracing and identifying those products, and the metabolic pathways involved in their formation, are still challenging within complex environmental samples. We applied stable isotope-assisted metabolomics (SIAM) to polycyclic aromatic hydrocarbon-contaminated soil collected from a wood treatment facility. Soil samples were separately spiked with uniformly 13C-labeled fluoranthene, pyrene, or benzo[a]anthracene at a level below that of the native contaminant and incubated for 1 or 2 weeks under aerobic biostimulated conditions. Combining high-resolution mass spectrometry and automated SIAM workflows, we propose chemical structures of metabolites and metabolic pathways in the soil. Ring-cleavage products, including previously unreported intermediates such as C11H10O6 and C15H12O5, were detected originating from fluoranthene and benzo[a]anthracene, respectively. Sulfate conjugates of dihydroxy compounds were found as major metabolites of pyrene and benzo[a]anthracene, suggesting the potential role of fungi in their biotransformation in soils. A series of unknown N-containing metabolites were identified from pyrene, but their structural elucidation requires further investigation. Our results suggest that SIAM can be successfully applied to understand the fate of organic pollutants in environmental samples, opening lines of evidence for novel mechanisms of microbial transformation within such complex matrices.
Funding Information
  • National Institute of Environmental Health Sciences (P30ES010126, P42ES005948)
  • H2020 Marie Sklodowska-Curie Actions (661361)

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