Predominance of industrial Pb in recent snow (1994–2004) and ice (1842–1996) from Devon Island, Arctic Canada
Bibliographic record
Abstract
Atmospheric Pb contamination was studied using snow and ice from the Canadian arctic. Forty‐five samples representing the past ten years of snow accumulation on Devon Island contain an average of 45.2 pg/g of Pb but only 0.43 pg/g of Sc. The average ratio of Pb to Sc (105) is far greater than that of soil‐derived dust particles (in the range 1 to 5) which indicates that ca. 95 to 99% of recent Pb is anthropogenic. Isotopic analyses (206Pb, 207Pb, 208Pb) confirm that anthropogenic sources continue to dominate atmospheric Pb inputs. Unlike snow from Greenland which receives Pb predominantly from the U.S. (206Pb/207Pb ≈ 1.2), snow from Devon Island is less radiogenic (206Pb/207Pb ≈ 1.15). There are pronounced seasonal variations, and the snow samples containing the greatest Pb enrichments are from winter when the Arctic is dominated by air masses originating in Eurasia. While the elimination of gasoline lead additives in Europe, North America and Japan has helped to reduce Pb emissions during the past two to three decades, aerosols in the Arctic today are still highly contaminated by industrial Pb.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| 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".