Hexachlorobutadiene (HCBD) contamination in the Arctic environment: A review
Bibliographic record
Abstract
Hexachlorobutadiene (HCBD) is a halogenated hydrocarbon that is primarily produced as an unintentional byproduct in the manufacture of chlorinated solvents. Similarities between HCBD and other persistent organic pollutants (POPs) led to its listing in 2015 for global regulation under the Stockholm Convention on POPs. HCBD's toxicity and propensity for long-range transport means there is special concern for its potential impacts on Arctic ecosystems. The present review comprehensively summarizes all available information of the occurrence of HCBD in the Arctic environment, including its atmospheric, terrestrial, freshwater and marine ecosystems and biota. Overall, reports of HCBD in Arctic environmental media are scarce. HCBD has been measured in Arctic air collected from monitoring stations in Finland and Canada, yet there is a dearth of data for other abiotic matrices (i.e. soils, sediments, glacier ice, freshwaters and seawater). Low HCBD concentrations have been measured in Arctic terrestrial and marine biota, which is consistent with laboratory studies that indicate that HCBD has the potential to bioaccumulate, but not to biomagnify. Available data for Arctic biota suggest that terrestrial birds and mammals and seabirds, have comparatively higher HCBD concentrations than fish and marine mammals, warranting additional research. Although spatial and temporal trends in HCBD concentrations in the Arctic are currently limited, future monitoring of HCBD in the Arctic will be important for assessing the impact of global regulations newly-imposed by the Stockholm Convention on POPs.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.004 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".