Time Domain Reflectometry Measurements of Solute Transport across a Soil Layer Boundary
Bibliographic record
Abstract
The mechanisms governing solute transport through layered soil are not fully understood. Solute transport at, above, and beyond the interface between two soil layers during quasi‐steady‐state soil water movement was investigated using time domain reflectometry (TDR). A 0.26‐m sandy loam layer was packed on top of a 1.35‐m fine sand layer in a soil column (0.15‐m i.d.). Soil water content (θ) and bulk soil electrical conductivity (EC b ) were measured by 50 horizontal and 2 vertical TDR probes. A new TDR calibration method that gives a detailed relationship between apparent relative dielectric permittivity ( K a ) and θ was applied. Two replicate solute transport experiments were conducted adding a conservative tracer (KCl) to the surface as a short pulse. The convective lognormal transfer function model (CLT) was fitted to the TDR‐measured time integral–normalized resident concentration breakthrough curves (BTCs). The BTCs and the average solute‐transport velocities showed preferential flow occurred across the layer boundary. A nonlinear decrease in TDR‐measured θ in the upper soil toward the soil layer boundary suggests the existence of a 0.10‐m zone where water is confined towards fingered flow, creating lateral variations in the area‐averaged water flux above the layer boundary. A comparison of the time integral–normalized flux concentration measured by vertical and horizontal TDR probes at the layer boundary also indicates a nonuniform solute transport. The solute dispersivity remained constant in the upper soil layer, but increased nonlinearly (and further down, linearly) with depth in the lower layer, implying convective‐dispersive solute transport in the upper soil, a transition zone just below the boundary, and stochastic–convective solute transport in the remaining part of the lower soil.
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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 | 0.000 |
| 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 | 0.000 | 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".