Variation in Methane Hydrate Structure and Composition
Notice bibliographique
Résumé
Abstract Methane hydrates are now recognized to be present in substantial quantities along most ocean margins. Current estimates indicate that methane in hydrates exceeds fixed carbon in petroleum reserves by about a factor of three. This is a large potential source of energy, capable of lasting for centuries. In response, Japan, Korea, Norway, India and Canada are actively investigating the acquisition of methane from hydrates as an energy source. Their success could significantly restructure the global economy. While a large international focus is on methane hydrates as a source of energy, hydrates are also thought to influence ocean carbon cycling, global warming, and coastal sediment stability. Thus, methane hydrates are a significant emerging research issue. While the global distribution and quality of hydrate fields are certainly being pursued, this presentation describes more fundamental investigations of naturally formed methane hydrates. Specifically, the Naval Research Laboratory (NRL) has initiated research on the influence of hydrates on ocean floor geoacoustical and geotechnical properties. In addition, NRL and Argonne National Laboratory (ANL) have studied methane hydrates from different regions of the world ocean for variations in structure and composition. This presentation compares the methane hydrate structure, composition, and source of carbon for samples taken from the Norwegian-Greenland Sea and the Gulf of Mexico. Structural analysis is compared using x-ray diffraction. Composition is described from gas chromatography, and the carbon source is identified with carbon isotope analysis. Introduction Methane hydrates vastly exceeds other carbon reservoirs in the ocean1. Research demonstrates that both thermogenic and biological carbon sources contribute to the formation of the methane hydrates2,3. There is a large variation in the sources of methane between ecosystems. The carbon cycling that controls methane production in the ocean floor is related to a complex mixture of biological, chemical and physical processes. Physical factors on the ocean floor relate to motion of the continental plates resulting in expulsion of fluids and volatile compounds, flows of geothermal energy toward the sediment-ocean interface, cold pressure mediated seeps of reduced compounds, and high levels of land based carbon transport to the ocean floor. These processes result in a variety of chemical speciation through key elemental pools that enhance microbial activity. For example, ocean floor thermal seeps have a high flux of reduced compounds, e.g. CH4, H2S and NH4, that supports the chemoautotrophic population. These cycles serve as the base of the food chain where enzymatic oxidation results in fixation of CO2 into cellular biomass. In active regions this results in CO2 serving as the terminal electron acceptor and methane production and fixation in hydrates. The variation in thermogenic and biological methane sources influences the hydrate content and structure. The degree that these factors contribute to the hydrate stability and formation warrants further research. Results from this research topic will contribute to methane hydrate mining strategies, understanding of coastal stability and environmental health, analysis of ocean carbon cycling, and predication of global warming.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
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) | 0,007 | 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 découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».