The Use of the ‘Ammonium Diffusion’ Method for d15N-NH4+ and d15N-NO3- Measurements: Comparison with Other Techniques
Bibliographic record
Abstract
Environmental Context. Nitrogen is an essential element for all living organisms, and its biogeochemical cycle is connected to the cycling of carbon, sulfur, phosphorous, oxygen, and trace metals. Measurement of the isotopic composition of ammonium (NH4+) and nitrate (NO3-) containing samples provides a better understanding of the nitrogen cycle. While the established ‘ammonium diffusion’ measurement has many advantages, it is not easy for inexperienced people to prepare samples. This paper shows how the method can be simplified, ideally for samples freshly collected from the field. Abstract. Several methods have been developed for nitrogen isotope measurements on ammonium (NH4+) and nitrate (NO3-) in solid or aqueous samples. We have tested the accuracy and reproducibility of the ammonium diffusion method for d15N measurements on NH4+ and NO3- and compared this technique to other established methods. Our results show that the ammonium diffusion technique is capable of generating accurate and reproducible d15N values for minute quantities of NH4+-N and NO3--N in aqueous samples, if sufficient care is taken to minimize nitrogen blanks and to optimize the extraction procedure. Hence, the ammonium diffusion method offers an attractive alternative to more labour-intensive and costly methods for determining nitrogen isotope ratios of NH4+ and NO3- in aqueous samples.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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 teacher head, 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".