Multi-model study of mercury dispersion in the atmosphere: Atmospheric processes and model evaluation
Bibliographic record
Abstract
Abstract. Current understanding of mercury (Hg) behaviour in the atmosphere contains significant gaps. Some key characteristics of Hg processes including anthropogenic and geogenic emissions, atmospheric chemistry, and air-surface exchange are still poorly known. This study provides a complex analysis of processes governing Hg fate in the atmosphere involving both measurement data from ground-based sites and simulation results of chemical transport models. A variety of long-term measurements of gaseous elemental Hg (GEM) and reactive Hg (RM) concentration as well as Hg wet deposition flux has been compiled from different global and regional monitoring networks. Four contemporary global-scale transport models for Hg were applied both in their state-of-the-art configurations and for a number of numerical experiments aimed at evaluation of particular processes. Results of the model simulation were evaluated against measurements. As it follows from the analysis the inter-hemispheric gradient of GEM is largely formed by the spatial distribution of anthropogenic emissions which prevail in the Northern Hemisphere. Contribution of natural and secondary emissions enhances the south-to-north gradient but their effect is less significant. The atmospheric chemistry does not affect considerably both spatial distribution and temporal variation of GEM concentration in the surface air. On the other hand, RM air concentration and wet deposition are largely defined by oxidation chemistry. The Br oxidation mechanism allows successfully reproducing observed seasonal variation of the RM / GEM ratio in the near-surface layer, whereas it predicts maximum in wet deposition in spring instead of summer as observed at monitoring sites located in North America and Europe. Model runs with the OH chemistry correctly simulate both the periods of maximum and minimum values and the amplitude of observed seasonal variation but lead to shifting the maximum RM / GEM ratios from spring to summer. The O3 chemistry does not provide significant seasonal variation of Hg oxidation. Thus, performance of the considered Hg oxidation mechanisms differs in reproduction of different observed parameters that can imply possibility of more complex chemistry and multiple pathways of Hg oxidation occurring concurrently in various parts of the atmosphere.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".