A Continental and Marine-Influenced Tree-Ring Mercury Record in the Old Crow Flats, Yukon, Canada
Bibliographic record
Abstract
Gaseous elemental mercury (Hg 0 ) concentrations in the atmosphere have been increasing due to anthropogenic activities since the onset of colonial mining in the 17th century. However, accurate measurements of atmospheric Hg, including temporal trends, are mostly limited to recent decades. Natural environmental archives including tree rings show promise for reconstructing atmospheric concentrations of Hg 0 . In this paper, we present a new white spruce ( Picea glauca ) tree-ring Hg record (1696–2005) from the Old Crow Flats in northern Yukon. The record we present shows an increase in tree-ring Hg concentration (a proxy for gaseous Hg 0 concentration) between 1748 and 1990 at a rate of +3.3% per year. A decrease in measured Hg is observed at the end of the record between 1990 and 2005, which may reflect the success of international regulations to reduce emissions including Hg. When compared with two other sites (a continental and marine location) in northwest Canada, there is not only some coherence in Hg trends at the regional scale but also some unique differences, suggesting that the location may influence atmospheric Hg 0 available for assimilation. Further local factors within a site, such as soil moisture, may also affect the efficiency of this uptake. Results from this study highlight the need to better understand intra-site and inter-site differences in measured tree-ring Hg, and we recommend the continued development of a spatially resolved tree-ring Hg network in the northern boreal forest. Such records will be useful for developing better atmospheric Hg and global Hg models.
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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 | 0.002 |
| Science and technology studies | 0.001 | 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".