Infiltration of Sulfate to Enhance Sulfate‐Reducing Biodegradation of Petroleum Hydrocarbons
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Notice bibliographique
Résumé
Abstract The lack of sufficient electron acceptors, particularly sulfate, can limit the rate of biodegradation of petroleum hydrocarbons (PHCs). Hence, there is a growing interest by remediation practitioners to deliver sulfate to a PHC impacted saturated zone to enhance biodegradation. When shallow contamination is present in a relatively permeable aquifer and site constraints allow, a cost‐effective approach is to apply sulfate on the ground surface. In this investigation a pilot‐scale experiment was conducted to increase our understanding of the delivery of sulfate using a surface‐based method and the resulting impact on a shallow PHC contaminated aquifer. A surficial infiltration pond positioned on the ground surface above a well‐characterized residual PHC source zone was used to control sulfate dosing. A high‐resolution network near the infiltration pond and downgradient of the source zone was employed to monitor relevant geochemical indicators and PHC concentrations. Compound‐specific isotope analysis (CSIA) was used to identify biodegradation patterns and to investigate the occurrence of microbial sulfate reduction. Selected metabolites and reverse‐transcriptase quantitative polymerase chain reaction analyses of expressed biodegradation genes (as mRNA) were also used to characterize the response of indigenous microorganisms (especially sulfate‐reducing bacteria) to the added sulfate. Three sulfate application episodes (5000 L each) at various Na 2 SO 4 concentrations were allowed to infiltrate under a constant hydraulic head. Although the applied sulfate solution was impacted by density‐driven advection, detailed monitoring data indicated that the sulfate‐enriched water mixed with upgradient groundwater as it migrated downward through the residual PHC zone and formed a co‐mingled downgradient plume with the dissolved PHC compounds. The enrichment of δ 34 S of sulfate in conjunction with a decrease in sulfate concentration showed the occurrence of sulfate reduction due to the applied sulfate. Increased dissolved inorganic carbon (DIC) concentrations associated with a shift toward more depleted values of δ 13 C of DIC was indicative of an input of isotopically depleted DIC from biodegradation of PHCs. Despite fluctuations in benzene, toluene, and o ‐xylene (BTX) concentrations, the CSIA data for BTX showed that these compounds were biodegraded. The biomarker data provided supporting evidence that toluene and o ‐xylene were undergoing anaerobic biodegradation due to sulfate reduction. This study provides insight into factors controlling surface‐based delivery of sulfate to shallow PHC impacted groundwater systems, and the value of isotopic and molecular‐biological procedures to augment conventional monitoring tools.
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Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle