Geochemical perspectives from the past: understanding the natural enrichment of Cd in pre-industrial and pre-anthropogenic aerosols using polar ice and peat cores from remote locations
Notice bibliographique
Résumé
Cadmium (Cd) is a potentially toxic chalcophile element with profound health consequences when organisms are exposed to elevated concentrations. Cadmium is emitted to the atmosphere through various industrial processes (metallurgical smelting, coal combustion), but it is also derived from natural sources (volcanic emissions, wind-borne soil particles). In contemporary air samples collected within urban areas across the globe, Cd enrichment factors (EF) relative to the Upper Continental Crust (UCC) are often up to 100, and are typically interpreted as reflecting inputs exclusively from anthropogenic activities. This presentation reports on the range of Cd EF values in aerosol archives from various locations representing up to 15,500 years of atmospheric Cd deposition, including: (i) Polar ice collected at Devon Island (Nunavut, Canada), and; (ii) Peat from ombrotrophic bogs collected at Etang de la Gruère (Jura Mountains, Switzerland), Birch Mountain (BMW) and Caribou Mountain Wildlands (CMW) (Alberta, Canada), and Drizzle Bog (DB) (British Columbia, Canada). The ice samples were melted and acidified, and the peat samples digested, with double sub-boiled concentrated nitric acid, analyzed using SF-ICP-MS and ICP-QMS, respectively. All analyses were undertaken in metal-free, ultraclean laboratories. Age-dating of ice was obtained using electrical conductivity and oxygen isotopes, and the peat samples with conventional 14C AMS and 210Pb. Cadmium concentrations were normalized to the conservative lithophile reference elements (Sc, Ti, and Th) to calculate the EF. Regardless of the reference element and the compilation selected for the UCC, the EF in old and ancient samples was often very high: up to 4000 in ice and up to 400 in peat bogs. These profound enrichments of Cd and dramatic variation pre-dating anthropogenic activities suggest that either natural emissions of Cd were not constant, or that non-crustal sources of Cd have been underestimated. In the ice cores, the period with the lowest and most constant Cd concentrations was found between 2,500 and 4,500 years BP (0.92 ± 0.13 pg g-1), with an average EFSc of 107. Samples from the early and middle Holocene (4,500 to 12,000 years BP) contained higher concentrations of Cd (2.43±0.50 pg g-1), with an average EFSc of 255. In the Swiss bog, the Cd EFTh ranged from 9 to 800, and was more stable in the period between 9,000 to 11,000 years BP (14±5). In the pre-industrial layers of peat bogs from remote locations in Canada, the EFTh values averaged 30 (DB), 54 (BMW) and 167 (CMW). These variations in Cd enrichment levels likely reflect differences in contributions from natural sources: volcanic activity, deposition of fine airborne soil particles, and natural forest fires. The biological uptake and recycling of Cd observed in some terrestrial plants and corresponding enrichment in humus may also play a role, but these potential contributions have received limited attention. The very high EF found in contemporary aerosols, recent peat layers and modern snow samples should be interpreted with caution pending improved understanding of the sources of natural aerosol Cd enrichments, and associated processes.
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 | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,002 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| 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 ».