Identifying Sources and Biomagnification of Persistent Organic Contaminants in Biota from Mountain Streams of Southwestern British Columbia, Canada
Bibliographic record
Abstract
We assessed whether biota occupying mountain streams accumulate and biomagnify remotely derived organic pollutants originating from atmospheric inputs to snowpack and glacial runoff and from marine sources introduced by migrating anadromous salmon. Several persistent organic pollutants including polychlorinated biphenyls (PCBs), p,p'-dichloro-diphenyl-dichloroethylene, hexachlorobenzene, and trans-nonachlor were commonly detected in benthic invertebrates, salmon fry (Oncorhynchus spp.), and eggs of an aquatic passerine, the American dipper (Cinclus mexicanus) from the Chilliwack River watershed, British Columbia, Canada. Total PCBs and several organochlorines (OCs) biomagnified from benthic invertebrate composites to salmon fry to dipper eggs. Invertebrate samples generally did not differ significantly in contaminant burdens between the river main stem where salmon are more abundant and higher-elevation tributaries where the salmon density is lower. Concentrations of total OCs and total PCBs in dipper eggs were positively related to drainage basin area and collection year but not to elevation. No differences in PCB congener patterns existed between dipper egg samples from the Chilliwack watershed and other watersheds in southwestern British Columbia. However, principal component analysis revealed significant spatial differences in egg PCB congener patterns between the main Chilliwack River and the higher-elevation tributaries. This difference was primarily due to a greater occurrence of lower chlorinated PCB congeners (66 and 105) in dipper eggs collected from the tributaries and higher loadings of the more stable and persistent congeners (153, 138, 130, and 128) in eggs from the river main stem. The results suggest that atmospheric sources are the main contributor of contaminants detected in biota from the region and that biomagnification is a common pathway for accumulation in lotic predators such as the American dipper.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 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".