Landscape fluxes and dry deposition velocity of ammonia near a cattle feedlot using flux gradient approach
Bibliographic record
Abstract
Concentrated animal feeding operations (CAFOs) are emission hotspots of ammonia (NH3). The NH3 emitted from these hotspots can be locally recaptured by the surrounding vegetation, mainly due to dry deposition. This deposition can either have beneficial fertilizing effects for N-limited ecosystems or pose adverse impacts on sensitive ecosystems. However, there is a lack of direct measurements of NH3 deposition near hotspots. We conducted two field campaigns to investigate the landscape NH3 fluxes over the barley (winter), lentil (winter), and fallow (summer) fields adjacent to an intensive beef cattle feedlot in southeast Australia. The flux measurements were segregated into periods when the measurement location was upwind of the feedlot or downwind. Upwind of the feedlot, we observed upward fluxes (surface emissions) over the fallow and barley sites with daily means (± standard error) of 0.16 ± 0.02 and 0.007 ± 0.012 μg NH3 m-2 s-1, and downward fluxes (deposition) over the lentil site with a daily mean of -0.022 ± 0.007 μg NH3 m-2 s-1. These measurements indicated the NH3 compensation point for barley was approximately 6.2 μg m-3 (equivalent to the background atmospheric NH3 concentration), and the NH3 compensation point for lentils was lower than 3.4 μg m-3. Downwind of the feedlot, we observed downward fluxes at all sites with daily means of -0.57 ± 0.09 μg NH3 m-2 s-1 for the barley site, -1.26 ± 0.17 μg NH3 m-2 s-1 for the lentil site, and -0.58 ± 0.12 μg NH3 m-2 s-1 for the fallow site; the mean deposition velocities over the barley, lentil, and fallow sites were 0.74, 0.82 and 0.78 cm s-1. Based on the frequency of upwind and downwind periods, we estimate that the accumulated N inputs to the barley, lentil and fallow fields during each campaign were 4.5, 14.8 and 4.3 kg N ha-1, indicating that the deposition of NH3 emitted from the feedlot serves as a significant source of N input to its adjacent fields. Our study can provide valuable information on NH3 exchange between vegetation and atmosphere, and extend our understanding of the fate of NH3 emitted from hotspots.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".