Production and Release of Molecular Bromine and Chlorine from the Arctic Coastal Snowpack
Bibliographic record
Abstract
Atmospheric bromine and chlorine atoms have a significant influence on the pathways of atmospheric chemical species processing. The photolysis of molecular halogens and subsequent reactions with ozone, mercury, and hydrocarbons are common occurrences in the Arctic boundary layer during spring, following polar sunrise. While it was recently determined that Br 2 is released from the sunlit surface snowpack, the source(s) and mechanisms of Cl 2 and BrCl production have remained unknown. Current efforts to model Arctic atmospheric composition are limited by the lack of knowledge of the sources and emission rates of these species. Here, we present the first simultaneous direct measurements of Br 2, Cl 2, and BrCl in snowpack interstitial air, as well as the first measured emission rates of Br 2 and Cl 2 out of the snowpack into the atmosphere. Using chemical ionization mass spectrometry, Br 2, Cl 2, and BrCl were observed to be produced within the tundra surface snowpack near Utqiaġvik, AK, during Feb 2014, following both artificial and natural irradiation, consistent with a photolytic production mechanism. Maximum Cl 2 and Br 2 fluxes from the snowpack to the overlying atmosphere were quantified and reached maxima at mid-day during peak radiation. In-snowpack Br 2 and BrCl production was enhanced, with Cl 2 production reduced, at air temperatures below the eutectic point for the formation of NaCl·2H 2 O, suggesting limited chloride availability, as compared to production at air temperatures above this eutectic point. These new observations improves the ability of the community to simulate Arctic boundary layer composition and pollutant fate.
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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 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.000 | 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".