Quantitative analysis of seabed mixing and intertidal zone discharge in coastal aquifers
Bibliographic record
Abstract
Contaminant loading from an inland source zone to the nearshore marine environment is examined using a saturated‐unsaturated simulation model which incorporates both the influence of the growth and the extinction of the seepage face in the intertidal zone and the inclusion of hydromechanical stress coupling due to tidal loading. The system analyzed represents a site where an unconfined aquifer extends offshore with a broad intertidal zone. The volumetric discharge of groundwater in the intertidal zone dominates the discharge occurring beyond the low‐tide line. For most of the cases examined, within the intertidal zone, the recirculated saline component of the discharge is greater than the freshwater component. The majority of the contaminant mass exits through the seepage face located above the instantaneous tide line. The peak contaminant loading rate occurs around the time of the falling midtide. At low tide, the contaminant loading rate is more than 2 orders of magnitude lower than the peak rates, even though groundwater discharge rates are highest as low tide is approached. Sensitivity studies indicate that the relative proportion of recirculated intertidal zone discharge to fresh intertidal zone discharge is most sensitive to the magnitude of the freshwater flux, the spatial variation of the outflow across the intertidal zone as influenced by anisotropy in hydraulic conductivity, and tidal pumping as influenced by specific storage. Dilution of contaminant concentrations due to mixing with seawater beneath the sediment‐water interface is represented in terms of a dilution factor, defined relative to the onshore source concentration. For our base case, the dilution factor for the contaminant concentration averaged over one tidal cycle at the high‐tide, midtide, and low‐tide lines was 1.3, 3.9, and 560, respectively. The key factors determining contaminant dilution at the sediment interface are location within the intertidal zone and the vertical extent of the contaminant plume as it enters the intertidal zone.
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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 | 0.002 |
| 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 | 0.001 | 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 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".