Lethal and sub-lethal defects demonstrate the chronic toxicity of chemically-dispersed diluted bitumen to rainbow trout embryos (Oncorhynchus mykiss)
Bibliographic record
Abstract
Addition of a low molecular weight diluent to raw bitumen from Alberta’s Oil Sands produces diluted bitumen (dilbit), a physically and chemically distinct product from conventional oils. While thousands of kilometers of pipeline carry dilbit across Canada, relatively few studies have documented its environmental behaviour and toxicity to developing fish in the event of a spill to freshwater. In response, this study demonstrated exposure-response relationships between dilbit at a gradient of concentrations and toxicological responses of rainbow trout embryos under standardized laboratory conditions. Chronic toxicity was measured by exposing rainbow trout embryos for 25 days to two different winter dilbit blends, Access Western Blend (AWB) and Cold Lake Blend (CLB). Chemical dispersion of hydrocarbons from AWB and CLB dilbit into water (producing chemically enhanced water accommodated fractions, CEWAFs) was used to prepare exposure solutions. Endpoints to characterize chronic toxicity included mortality, impairment of growth and development, and select morphological deformities collectively called blue sac disease (BSD). Results indicated that cumulative mortality and the prevalence of sub-lethal defects (i.e. impairment of growth and development and onset of BSD) increased with increasing exposure concentration of dilbit CEWAF in water. Additionally, at the same volume of CEWAF, CLB had a higher total petroleum hydrocarbon content and higher lethal toxicity to rainbow trout embryos (25-d LC50 = 1200 g/L) than AWB (25-d LC50 = 1627 g/L). AWB and CLB were 2 and 2.7 times more toxic respectively when compared to a light crude oil (22-d LC50 = 3281 g/L), and 3.4 and 2.5 times less toxic respectively when compared to a heavy fuel oil (25-d LC50 = 473 g/L). This research contributes to developing a dilbit-specific assessment of toxicity and potential impacts (i.e., recruitment failure and declining populations of fish species whose spawning coincides with an oil spill) if the product is spilled into a freshwater environment.
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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".