Halogen activation in the plume of Masaya volcano: field observations and box model investigations
Bibliographic record
Abstract
Abstract. Volcanic emissions are a source of halogens to the atmosphere. Rapid reactions convert the initially emitted hydrogen halides (HCl, HBr, HI) into reactive species e.g. BrO, Br2, BrCl, ClO, OClO and IO. The activation reaction mechanisms in the plume consume ozone (O3), which is entrained by in-mixed ambient air. In this study, we present observations of the oxidation of bromine, chlorine and iodine during the first 11 minutes after emission, investigating the plume of Santiago Crater of Masaya volcano in Nicaragua. Two field campaigns were conducted, in July 2016 and September 2016. The sum of the reactive species of the respective halogens were determined by gas diffusion denuder sampling followed by GC-MS analysis, while the total amounts of halogens and sulfur amounts were obtained by alkaline trap sampling with subsequent IC and ICP-MS measurements. Both ground and airborne sampling with an unmanned aerial vehicle (including a denuder sampler in combination with an electrochemical SO2 sensor) was performed at different distances from the crater rim. The in-situ measurements were accompanied by remote sensing observations (DOAS). For bromine, the reactive fraction increased from 0.20 ± 0.13 at the crater rim to 0.76 ± 0.26 at 2.8 km downwind, while chlorine showed an increase of the reactive fraction from (2.7 ± 0.7) × 10−4 to (11 ± 3) × 10−4 in the first 750 m. Additionally, a reactive iodine fraction of 0.3 at the crater rim and 0.9 at 2.8 km was measured. No significant increase in BrO / SO2 molar ratios was observed with the estimated age of the observed plume ranging from 1.4 min to 11.1 min. This study presents a comprehensive gas diffusion denuder data set on reactive halogen species and compares BrO / SO2 ratios with the sum of all reactive Br species. With the observed field data, a chemistry box model (CAABA/MECCA) enabled the reproduction of the observed progression of the reactive bromine to total bromine ratio. An observed contribution of BrO to the reactive bromine fraction of about 10 % was reproduced in the first minutes of the model run. The model results emphasize the importance of ozone entrainment into the plume for the reproduction of the measured reactive bromine formation and the dependence on the availability of HXOY and NOX.
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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 | 0.000 | 0.000 |
| 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".