Phytoremediation of 25+ Years Weathered Petroleum Contamination with Symbiotic Arbuscular Mycorrhizal Fungi and <i>Bacillus subtilis</i> ATCC 21332
Bibliographic record
Abstract
Abstract Petroleum hydrocarbon (PHC) contamination affects approximately 60% of Canadian contaminated sites, with the boreal ecozone facing acute exposure from industrial activities. This study evaluated the long-term effectiveness of plant-microbe enhanced phytoremediation of 25+ years weathered PHC-contaminated field soil over a 24-month period. Five native or naturalized plant species (three tufted grasses, a forb, and a tree) were tested across two contaminated soils and a control to compare remediation efficacy and plant health: 25,700 mg/kg total petroleum hydrocarbons (TPH) and a 1:1 contaminated and background site soil mixture (12,600 mg/kg TPH). Soil treatments included a Plants-Only Control, Arbuscular Mycorrhizal Fungi (AMF), plant-growth-promoting-rhizobacterium - Bacillus subtilis , and AMF+ B. subtilis . Plant inoculation significantly improved remediation compared to natural attenuation (No Plants Control) in both PHC-contaminated soils. AMF-based treatments significantly remediated both soils: AMF in the 25,700 mg/kg TPH soil (74% mean TPH remediation) and AMF+ B. subtilis in the 12,600 mg/kg TPH soil (96% remediation). In the 12,600 mg/kg TPH soil, all treatments successfully reduced PHC levels to below federal and provincial thresholds (≥95% removal) within 17 months. Picea mariana (black spruce) and Andropogon gerardii (big bluestem) above- and below-ground biomasses were not significantly impaired by the 25,700 and 12,600 mg/kg TPH soils, indicating their suitability for site remediation. B. subtilis significantly improved above-ground biomass and plant height and is therefore recommended for co-inoculation with AMF. These findings demonstrate that AMF-enhanced phytoremediation represents a highly effective, sustainable approach for long-term PHC remediation in Canadian boreal ecosystems, offering significant advantages over natural attenuation processes alone. Highlights AMF-based treatments achieved highest PHC removal in 25+ year weathered boreal soils Prairie grasses remediated 12,600 mg/kg TPH soil by >95% in AMF+ B. subtilis treatment Enhanced Picea mariana (black spruce) biomass and moisture in 25,700 mg/kg TPH soil Bacillus subtilis significantly enhanced plant above-ground biomass and height AMF helped maximize PHC remediation, while B. subtilis promoted plant growth
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".