The Characterization of Ammonia Sources in Forested, Urban and Agricultural Areas
Bibliographic record
Abstract
To better characterize NH3 sources, field campaigns were conducted in a Colorado montane forest, the Salt Lake City urban area, and an agricultural field south of Ottawa. An Ambient Ion Monitor coupled with Ion Chromatographs (AIM-IC) was utilized in two campaigns to measure gas phase NH3 and particle phase NH4+ (pNH4+), in addition to other significant gases and PM2.5 chemical components (e.g. HNO3, SO2, HCl, pCl-, pNO3-, pSO42-, pNa+, pK+, pCa2+, and pMg2+). Measurement-based estimates of NH3 fluxes in the montane forest showed the soil is the predominant NH3 source. The changes observed in soil NH4+ content implied the indirect role of soil microbial processes on soil NH3 emissions. In Salt Lake City, where wintertime pollution is dominated by NH4NO3, my observations revealed the potential impact of mineral dust on the HNO3 availability, which was examined by thermodynamic aerosol modeling. Surface footprints derived from a Stochastic Time-Inverted Lagrangian Transport (STILT) model indicated that area sources are responsible for 78 % of the total NH3 emissions impacting the measurement site. Observed tracer relationships of NHx (NH3+pNH4+) with CO and NOx for each emissions sector (area, mobile, nonroad, and point) showed NH3 emissions from all source sectors are underestimated. To directly measure the surface-atmosphere exchange, i.e. flux, a continuous online Relaxed Eddy Accumulation coupled with Ion Chromatographs (REA-IC) was developed. The REA-IC was deployed in a urea-fertilized corn field in 2017 and 2018. Developments following the 2017 deployment led to improved 2018 flux measurements, in which the flux detection limit ranges ± 2 ng m-2 s-1 to ± 137 ng m-2 s-1. The REA-IC measurements showed average NH3 emissions of 39 ± 12 ng m-2 s-1 from August to October 2018 indicating that NH3 emissions can also occur later in the growing season. Afin de mieux caractériser les sources de NH3, des campagnes sur le terrain ont été menées dans une forêt de montagne du Colorado, la zone urbaine de Salt Lake City et un champ agricole au sud d’Ottawa. Un moniteur d’ions ambiant couplé à des chromatographes ioniques (AIM-IC) a été utilisé dans deux campagnes pour mesurer le NH3 en phase gazeuse et le NH4 + en phase particulaire (pNH4 +), en plus d’autres gaz importants et de composants chimiques contenant de la PM2.5 (HNO3, SO2, HCl, etc.) , pCl-, pNO3-, pSO42-, pNa +, pK +, pCa2 + et pMg2 +). Les estimations des flux de NH3 basées sur la mesure dans la forêt de montagne ont montré que le sol constituait la principale source de NH3. Les changements observés dans la teneur en NH4 + du sol impliquent le rôle indirect des processus microbiens du sol sur les émissions de NH3 du sol. À Salt Lake City, où le NH4NO3 domine dans la pollution hivernale, mes observations ont révélé l'impact potentiel des poussières minérales sur la disponibilité de HNO3, qui a été examiné par modélisation thermodynamique par aérosol. Les empreintes de surface dérivées d'un modèle de transport lagrangien à inversion temporelle stochastique (STILT) ont indiqué que les sources locales étaient responsables de 78% des émissions totales de NH3 ayant une incidence sur le site de mesure. Les relations observées entre les traceurs de NHx (NH3 + pNH4 +), de CO et de NOx pour chaque secteur d'émissions (zone, mobile, non routier et ponctuel) ont montré que les émissions de NH3 provenant de tous les secteurs sources étaient sous-estimées. Pour mesurer directement l’échange surface-atmosphère, c’est-à-dire le flux, une accumulation continue en ligne de tourbillons décontractés couplée à des chromatographes à ions (REA-IC) a été développée. Le REA-IC a été déployé dans un champ de maïs fertilisé à l'urée en 2017 et 2018. Les développements consécutifs au déploiement en 2017 ont permis d'améliorer les mesures de flux en 2018, dans lesquelles la limite de détection du flux se situe dans une plage de ± 2 ng m-2 s-1 à ± 137 ng. m-2 s-1. Les mesures REA-IC ont révélé des émissions moyennes de NH3 de 39 ± 12 ng m-2 s-1 d'août à octobre 2018, ce qui indique que les émissions de NH3 peuvent également se produire plus tard au cours de la saison de croissance.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".