Global atmospheric As and Bi contamination preserved in 3000 year old Arctic ice
Bibliographic record
Abstract
Despite its growing environmental significance, there are no detailed historical records of atmospheric As deposition for the Northern Hemisphere. Having overcome the severe analytical challenges in measuring As in polar ice, and using an Arctic ice core representing ∼16 ka of snow accumulation, we present a complete record of atmospheric As deposition for this period which reveals significant contamination beginning 3000 years ago. While Pb enrichments unequivocally increased threefold above natural background levels during Greek/Phoenician, Roman, and Medieval periods, As is elevated by a factor of 5. Previous studies showed that these periods are not only enriched in Pb but also Sb: here we show significant contamination not only by As but also Bi, Cu, and Zn. The Pb isotope data reveal declines in the ratio 206 Pb/ 207 Pb which reflects the introduction Pb‐bearing aerosols from smelting of lead ores, but the metallurgy of copper ores must also have played a role. Taken together, these findings demonstrate a deeper, broader environmental significance of sulphide ore processing in antiquity, defining the origins of global atmospheric contamination for a suite of related elements and providing a new perspective on the start of the Anthropocene. In addition, the data indicate that by far the greatest As concentrations in the ice core are recorded during the Younger Dryas cold climate event centered around 12 ka B.P., demonstrating the strong link between global climate change and the atmospheric cycling of trace elements.
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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 | 0.001 | 0.001 |
| 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".