Stable Nitrogen Isotopes and Sourcing Groundwater Nitrate: A Field Study
Bibliographic record
Abstract
The use of nitrate-nitrogen isotopes to identify nitrate sources in-situ was examined in a surficial aquifer at a municipal wastewater lagoon site. A subsurface investigation revealed an effluent plume, defined by chloride concentrations, that permeates the entire aquifer in the centre but is limited to the top of the aquifer laterally. Nitrate occurs intermittently at the top of the aquifer except in the centre of the plume where it penetrates to greater depth. The limited extent of the nitrate plume suggests it is being removed by some mechanism. Stable nitrate-nitrogen isotope enrichment values of eight samples were compared to published data and suggest that effluent nitrate exists in the centre of the plume, while unidentified nitrate from diffuse sources exists both within the plume and regionally. The limited amount of data suggests that the method has promise for in-situ identification of septic-effluent nitrate but is inconclusive as to the source of other nitrates. Application as an effluent tracer is restricted to areas where denitrification does not limit the extent of nitrate contamination. The method does not preclude a thorough understanding of the hydrogeology and geochemistry. More data in similar environments are needed before the method can be applied practically in a deterministic manner.
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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 | 0.001 | 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 | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".