How the δ<sup>18</sup>O<sub>NO<sub>3</sub></sub> versus δ<sup>15</sup>N<sub>NO<sub>3</sub></sub> Plot Can Be Used to Identify a Typical Expected Isotopic Range of Denitrification for NO<sub>3</sub>-Impacted Groundwaters
Bibliographic record
Abstract
Stable isotope values of δ 15 N NO 3 and δ 18 O NO 3 of dissolved nitrate (NO 3 ) are commonly used to identify the occurrence of denitrification as there is a progressive increase of δ 15 N NO 3 and δ 18 O NO 3 values accompanied by a decrease in NO 3 concentration. Thus, denitrification results in a positive trendline on the dual plot of δ 18 O NO 3 versus δ 15 N NO 3 . The combination of two trendlines with different slopes provides the “typical expected isotopic range of denitrification (TEIRD)” on the δ 18 O NO 3 versus δ 15 N NO 3 plot. Many studies distinguished denitrified groundwaters by applying the TEIRD concept that is incorrectly introduced because it assumes a single NO 3 source even though multiple NO 3 sources exist. Also, most TEIRD applications rely on specific denitrification slopes although these are known to vary owing to the aquifer’s changing biogeochemical conditions. Alternatively, an accurate delineation of the TEIRD requires the identification of all potential NO 3 sources in aquifer with their measured or reconstructed δ 15 N NO 3 and δ 18 O NO 3 values. This allows then for an accurate TEIRD to be traced with two denitrification trendlines having a slope corresponding to that from the correlation of the measured δ 18 O NO 3 and δ 15 N NO 3 values. Ultimately, each NO 3 source can have a specific TEIRD, although denitrification trendlines for multiple NO 3 sources can feature the same slope within a single aquifer.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
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".