Sedimentary phosphorus speciation dynamics following artificial eutrophication of Lake 227, Experimental Lakes Area, Ontario, Canada
Notice bibliographique
Résumé
Stringent environmental policies in many countries have played an extensive role in reducing external phosphorus (P) loading to lakes from agriculture and urban sources. Nonetheless, such reductions in external P loading to many eutrophic lakes have not resulted in the expected concurrent restitution of water quality. Such a delayed recovery of many lakes is blamed both on internal loading of legacy P from lake sediments (i.e., benthic recycling) and the amplification of such internal P loading processes due to the reduction in external P concentrations. Hence, a detailed process understanding of P cycling at the sediment-water interface (SWI) is critical to understand nutrient loading, water quality and associated effects on lake water quality. Much of the work on sedimentary P cycling has traditionally focused on inorganic processes of soluble phosphate, particularly sorption to metals (Fe, Mn, Al) oxyhydroxides and clays. However, there is increasing recognition that organic forms of P, along with interactions between phosphate and humic substances, also play a decisive role in controlling P fluxes between sediments and the overlying water column. This study focused on gaining further understanding of the such processes through the collection of sediment cores from the oxygenated epilimnion and the mostly anoxic hypolimnion of Lake 227 of the Experimental Lakes Area (ELA) in Ontario, Canada. Since 1969, this unique experimental lake has been fertilized with phosphorus (P), which triggered a relatively rapid trophic transition from oligotrophic to eutrophic conditions. The cores contain a chronological record of changes in sediment burial rates and sediment P speciation across this trophic transition. Interpretation of such changes was undertaken by coupling results of chemical extractions with 210Pb sediment dating, 31P NMR, XANES and Mössbauer spectroscopy. The major sedimentary P fraction prior to lake enrichment starting in 1969 was organic P (POrg). Fertilization of the lake in 1969 coincided with significant increases in the accumulation rate of sediment, total organic carbon (TOC) and total P (TP), in addition to a marked relative contribution of NaHCO3 extractable P. The combined proportion of PHum and POrg desposited since artificial fertilization in 1969 account for ≥70% of total P burial in the sediments. The anticipated composition of such PHum fractions was hypothesized to be ternary phosphate (PO4) complexes with humic substances. In support of this, the strong linear correlation between P and iron (Fe) extracted by NaHCO3 implies a close association of the two elements in the humic fraction. Furthermore, XANES and Mössbauer spectra indicate that most Fe in the post-1969 sediments is conserved in the +3 oxidation state, which may be ascribed to the stabilization of reducible Fe by organic matter, partially due to the formation of ternary PO4-Fe(III)-humic complexes. Our findings suggest the artificial eutrophication of Lake 227 resulted in the accelerated accumulation of a large sedimentary reservoir of reactive sediment P that may drive continued internal P loading to the water column following the cessation of artificial fertilization.
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 machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 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) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».