Occurrences of Tire Rubber-Derived Contaminants in Cold-Climate Urban Runoff
Why this work is in the frame
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Bibliographic record
Abstract
Recent findings that 2-anilo-5-[(4-methylpentan-2-yl)amino]cyclohexa-2,5-diene-1,4-dione (6PPD-quinone), the transformation product of a common tire rubber antioxidant, is acutely toxic in stormwater-impacted streams has highlighted the need for a better understanding of contaminants in urban runoff. This study represents one of the first reports of 6PPD-quinone and other tire rubber-derived compounds in stormwater and snowmelt of a cold-climate Canadian city (Saskatoon, 2019–2020). Semiquantification of the five target compounds, N,N′-diphenylguanidine (DPG), N,N-dicyclohexylmethylamine (DCA), N,N′-dicyclohexylurea (DCU), 1-cyclohexyl-3-phenylurea (CPU), and 6PPD-quinone, revealed DPG was most abundant, with average concentrations of 60 μg L–1 in stormwater and 1 μg L–1 in snowmelt. Maximum observed concentrations of DPG were greater than 300 μg L–1, equivalent to loadings of 15 kg from a single rain event. These concentrations of DPG represent some of the highest reported in urban runoff globally. 6PPD-Quinone was detected in 57% (12/21) of stormwater samples with a mean concentration of approximately 600 ng L–1 (2019) and greater than 80% (28/31) of snowmelt samples with mean concentrations of 80–370 ng L–1 (2019 and 2020). Concentrations of 6PPD-quinone exceeded the acute LC50 for coho salmon (0.8–1.2 μg L–1) in greater than 20% of stormwater samples. Mass loadings of all target chemicals correlated well with roads and residential land-use area.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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 it