Tracing biogeochemical and microbial variability over a complete oil sand mining and recultivation process

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Oil sand mining significantly disturbs ecosystems, necessitating effective land reclamation strategies.
• Understanding the fate of organic matter and microbial communities during oil sand processing and reclamation is crucial for successful soil development.

Purpose of the Study:

• To investigate biogeochemical alterations in oil sands throughout processing, tailings management, and reclamation.
• To determine the influence of oil sand processing versus biological activity on organic matter, microbial abundance, and community structure.

Main Methods:

• Analysis of oil sand, mature fine tailings (MFTs), and peat-mineral mix (PMM) amended reclamation sites.
• Gas Chromatography-Mass Spectrometry (GC-MS) for oil-derived biomarkers and polycyclic aromatic hydrocarbons (PAHs).
• Quantification of cell abundances and microbial community structure analysis.

Main Results:

• Oil-derived biomarkers remained stable, while PAH patterns changed significantly along the process chain, with specific compounds altered or absent on reclamation sites.
• Reclamation sites showed significantly higher microbial cell abundances (10^8–10^9 cells g⁻¹) compared to oil sand and MFTs (10^7 cells g⁻¹).
• Nitrate and PMM-derived roots stimulated microbial growth, leading to increased microbial diversity on reclamation sites.

Conclusions:

• Biogeochemical changes observed are primarily attributed to biological activity and the addition of exogenous organic matter (PMM), not oil extraction or tailings management.
• Microbial community composition remained relatively stable throughout the entire process chain.
• Reclamation practices foster microbial growth and community development, essential for establishing new soils on disturbed lands.