Satellite evidence of substantial rain-induced soil emissions of ammonia across the Sahel
Notice bibliographique
Résumé
Atmospheric ammonia (NH 3 ) is a precursor to fine particulate matter formation and contributes to nitrogen (N) deposition, with potential implications for the health of humans and ecosystems. Agricultural soils and animal excreta are the primary source of atmospheric NH 3 , but natural soils can also be an important emitter. In regions with distinct dry and wet seasons such as the Sahel, the start of the rainy season triggers a pulse of biogeochemical activity in surface soils known as the Birch effect, which is often accompanied by emissions of microbially produced gases such as carbon dioxide and nitric oxide. Field and lab studies have sometimes, but not always, observed pulses of NH 3 after the wetting of dry soils; however, the potential regional importance of these emissions remains poorly constrained. Here we use satellite retrievals of atmospheric NH 3 using the Infrared Atmospheric Sounding Interferometer (IASI) regridded at 0.25 ∘ resolution, in combination with satellite-based observations of precipitation, surface soil moisture, and nitrogen dioxide concentrations, to reveal substantial precipitation-induced pulses of NH 3 across the Sahel at the onset of the rainy season in 2008. The highest concentrations of NH 3 occur in pulses during March and April when NH 3 biomass burning emissions estimated for the region are low. For the region of the Sahel spanning 10 to 16 ∘ N and 0 to 30 ∘ E, changes in NH 3 concentrations are weakly but significantly correlated with changes in soil moisture during the period from mid-March through April when the peak NH 3 concentrations occur ( r =0.28, p =0.02). The correlation is also present when evaluated on an individual pixel basis during April ( r =0.16, p <0.001). Average emissions for the entire Sahel from a simple box model are estimated to be between 2 and 6 mg NH 3 m −2 d −1 during peaks of the observed pulses, depending on the assumed effective NH 3 lifetime. These early season pulses are consistent with surface observations of monthly concentrations, which show an uptick in NH 3 concentration at the start of the rainy season for sites in the Sahel. The NH 3 concentrations in April are also correlated with increasing tropospheric NO 2 concentrations observed by the Ozone Monitoring Instrument ( r =0.78, p <0.0001), which have previously been attributed to the Birch effect. Box model results suggest that pulses occurring over a 35-day period in March and April are responsible for roughly one-fifth of annual emissions of NH 3 -N from the Sahel. We conclude that precipitation early in the rainy season is responsible for substantial NH 3 emissions in the Sahel, likely representing the largest instantaneous fluxes of gas-phase N from the region during the year.
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 | 0,000 | 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) | 0,001 | 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 ».