Effect of Carboxylic Acid Content on the Acute Toxicity of Oil Sands Naphthenic Acids
Bibliographic record
Abstract
Fractions of methylated naphthenic acids (NAs) isolated from oil sands process-affected waterwere collected utilizing Kugelrohr distillation and analyzed by proton nuclear magnetic resonance (1H NMR) spectroscopy. 1H NMR analysis revealed that the ratio of methyl ester hydrogen atoms to remaining aliphatic hydrogen atoms increased from 0.130 to 0.214, from the lowest to the greatest molecular weight (MW) fractions, respectively, indicating that the carboxylic acid content increased with greater MW. Acute toxicity assays with exposure to monocarboxyl NA-like surrogates demonstrated that toxicity increased with increasing MW (D. magna LC50 values of 10 +/- 1.3 mM and 0.59 +/- 0.20 mM for the respective lowest and highest MW NA-like surrogates); however, with the addition of a second carboxylic acid moiety, the toxicity was significantly reduced (D. magna LC50 values of 10 +/- 1.3 mM and 27 +/- 2.2 mM forthe respective monocarboxyl and dicarboxyl NA-like surrogates of similar MW). Increased carboxylic acid content within NA structures of higher MW decreases hydrophobicity and, consequently, offers a plausible explanation as to why lower MW NAs in oil sands process-affected water are more toxic than the greater MW NAs.
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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".