Spatial Variability of Long‐Term Chloride Transport under Semiarid Conditions: Pedon Scale
Bibliographic record
Abstract
Knowledge about the magnitude and variability of water and solute fluxes in semiarid environments is required to assess the environmental risk associated with contaminants in the vadose zone. The purpose of this study was to examine the pedon‐scale spatial variability in the transport of a chloride tracer after 34 yr at a site 50 km southwest of Saskatoon, SK. Soil cores were taken from two, pedon‐scale transects (transects encompassing many pedons), and solute transport was quantified for each depth breakthrough curve using the method of moments. Modal transport depth (depth of peak concentration) did not vary significantly over the length of the transects (average = 1.34 m), indicating a relatively uniform soil water balance at the pedon scale. Therefore, trends in central moments (mean travel depth ( E [ z ]), and variance about E [ z ]) were attributed to spatial variations in soil layering. Transport variance was negatively correlated ( P < 0.05) to the thickness of a fine‐textured, varved layer. The high water content (transport volume) of the varved layer decreased the velocity of the leading edge of the solute depth breakthrough curve which, over time, decreased V [ z ]. The two‐dimensional distribution of the chloride shows that the estimated horizontal velocity of the chloride pulse (approximately 25 mm yr −1 ) is more than twice the estimated downward, vertical velocity (approximately 11 mm yr −1 ). The large horizontal flow component is attributed to anisotropy in soil hydraulic properties. The significant influence of layers on convective and dispersive solute fluxes in a low flow, semiarid environment under natural conditions, complements previous observations in high flow field experiments where two‐ and three‐dimensional flow occurred along layer boundaries, and suggests anisotropy should be incorporated into transport models.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.005 | 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 teacher head, 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".