Velocities, Residence Times, Tracer Breakthroughs in a Vegetated Lysimeter: A Multitracer Experiment
Bibliographic record
Abstract
Abstract Flow velocities, residence times, and tracer breakthroughs at the lysimeter scale are affected by matrix properties and preferential flow. Despite their relevance to transport processes, however, the relative timing of preferential flow, and its link to transit times through the soil block, is still poorly described. Here we present and analyze tracer data from a 2.5 m3 vegetated lysimeter experiment where 18 mm of isotopically labeled water was added as a pulse and then followed with a series of tracer‐free controlled rainfall events for 5 months. A solution of two fluorobenzoid acid tracers was also injected and tracked. Time series of soil water samples at three different depths and bottom drainage samples were collected and analyzed. Unlike past lysimeter experiments, a willow tree grown within the lysimeter exerted strong evapotranspiration fluxes. By comparative analysis of soil water and bottom drainage samples, we show the presence of both translatory and preferential flow features reflecting the interplay of slow vertical percolation and fast recharge through macropores. We found that water ponding and evaporating from the top of the lysimeter after irrigation prompted samples to be highly and irregularly fractionated. Comparative analyses of multitracer breakthroughs (adjusted by removing fractionation effects) showed that fluorobenzoid acid tracers reached the bottom of the lysimeter earlier than the isotopes, likely due to the effect of plant uptake. Our results underscore the essential role of models to interpret tracer behavior and, critically, the importance of future experiments aimed at measuring the ages of the water abstracted by vegetation.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 | 0.001 |
| 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".