Bioavailability and Toxicity of Oil Trapped in River Sediments by Hyporheic Flows
Bibliographic record
Abstract
Transportation of large volumes of oil in Canada increases the likelihood of inland oil spills and river contamination. In oil spills to rivers, turbulence may disperse floating oil into the water column and hyporheic flows may carry oil droplets through the bed sediments, including sediments utilized by fish for reproduction. Research is needed to measure the toxicity of oil stranded on and trapped within sediments to fish, including assessment of diluted bitumen (dilbit) products that are frequently transported across Canada. The objectives of this thesis were to measure the toxicity of dilbits to rainbow trout with commonly used laboratory toxicity test methods; to develop laboratory methods to model oil droplet entrainment in hyporheic flows; and to measure oil droplet trapping in gravel by hyporheic flows, dissolution of oil into water, and bioavailability to rainbow trout. Research to address these objectives found that: Chemically dispersed dilbit and water flowing through gravel coated with dried films (dried oil films: DOF) of dilbit were chronically embryotoxic to rainbow trout alevins. Existing DOF methods were modified to assess oil droplet trapping in river gravels by hyporheic flows (trapped oil droplets: TOD). Increased oil mass loaded to or trapped in gravel (more trapping of higher viscosity oils) and increased oil surface area resulted in higher hydrocarbon concentrations in effluent. In DOF and TOD experiments, the concentration of hydrocarbons in water decreased over time, but the hydrocarbons were highly bioavailable to juvenile trout and were sustained at maximal levels over weeks of water flow. These findings contribute to the understanding of the fate of oil in rivers and the exposure of organisms that inhabit the hyporheic zone. Embryo-larval fish chronically exposed to oil trapped in river sediments could cause lethal or sublethal effects that reduce the number of fish that survive to adult stages and successfully reproduce. Population reductions in subsequent years could threaten the sustainability of fisheries. It is recommended that the potential fate of oil in the hyporheic zone be included in risk assessments and oil spill response to prevent and mitigate oil contamination of river sediments.
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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".