Numerical modelling of multi-component mass transport in a permafrost-impacted groundwater flow system
Bibliographic record
Abstract
A 3D numerical model has been developed to simulate groundwater flow, heat transport, and the transport and fate of reactive organic contaminants in a thawing permafrost environment.Insight is needed under such conditions as the climate warms and northern economic development accelerates, increasing the risk of groundwater resource contamination.The model includes coupled density-dependent groundwater flow, advective-conductive heat transport with latent heat and freeze/thaw, and advective-dispersive multi-component reactive mass transport.The reactive transport component can account for multicomponent aerobic and anaerobic biodegradation with multiple electron acceptors and microbial growth/decay, with temperature-dependent reaction rates governed by Monod kinetics.Model functionality and performance are tested on a 2D vertical-plane conceptual model of a field-scale cryo-hydrogeological system including thawing discontinuous permafrost and an evolving groundwater flow system.The test case includes a surface gasoline spill containing dissolved benzene, toluene, ethylbenzene, and xylene (BTEX), and a bulk residual component, migrating within a shallow aquifer and undergoing aerobic biodegradation.The presence of thawing permafrost, with associated effects on ice-fraction dependent relative permeability, strongly modulated subsurface hydraulic properties and connectivity, with subsequent changes to groundwater flow and mass transport pathways.Results show how evolution of the dissolved BTEX component plumes is controlled not only by the permafrost-impacted flow system, but also by the interacting thermal and chemical controls on overall biodegradation kinetics as the system evolves during permafrost thaw. 1
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".