Tracking 6PPD-Quinone Dynamics in a Coho Salmon-Bearing Stream Following Rain Reveals Elevated Concentrations for Multihour Periods During High Flow
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide Urban runoff mortality syndrome in coho salmon ( Oncorhynchus kisutch ) is attributed primarily to N -(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine-quinone (6PPD-Q), principally from car tires, that is delivered to streams by surface runoff. However, time-resolved stream 6PPD-Q concentration data remain scarce. We measured rainfall, discharge, and 6PPD-Q concentrations in an urban salmon-bearing stream over four rain events to capture the antecedent dry weather (baseflow) and the increased streamflow (stormflow). Portable autosamplers proved to be effective for continual water sampling. The resulting time series revealed 6PPD-Q flushing during stormflow, likely influenced by surface runoff from roads upstream. Following the initial rise in stream stage (+5% depth), mean 24 h time-averaged 6PPD-Q concentration was 45.0 ng/L, 25-fold higher than baseflow, and the mean 24 h load was 3.73 g, 220-fold higher than the preceding 24-h period. Measured 6PPD-Q concentrations, which peaked at 237.0 ng/L, exceeded the LC 50 reported for juvenile coho salmon for periods ranging from 3.5 to 18.7 h during rain events, but never during the preceding dry period. Accordingly, coho salmon habitat can be subjected to repeated pulses of 6PPD-Q over the course of the wet season during elevated streamflow periods, which may expose spawning adults, juveniles, and hatching fry to toxic concentrations for considerable periods.
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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".