Application of geophysics and numerical modelling in studying aquifer heterogeneity and nitrate transport, Abbotsford-Sumas aquifer, British Columbia, and Washington, USA
Bibliographic record
Abstract
Heterogeneity within the sand and gravel deposits of the Abbotsford-Sumas aquifer has a significant impact upon groundwater movement and nitrate transport. Using GPR and borehole logging, the scale of heterogeneity was determined, with fining upward sequences up to 5 m thick and continuous over 10’s of metres. Smaller heterogeneities were also identified visually in a local gravel pit. Various approaches were examined to represent this heterogeneity within a local groundwater flow mode l. The use of vertical anisotropy proved to be most realistic. Ages determined from the model were 60-80% lower than measured isotopic ages due to the inability to adequately represent the tortuosity of the flow paths. The spatial distribution and temporal variation of nitrate in the aquifer provided initial and calibration nitrate concentrations for the nitrate transport model. Nitrate concentrations thought to be reaching the aquifer based on recent BMPs are not sufficient to produce the observed nitrate concentrations.
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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 | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 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".