Mercury isotope fractionation during volatilization of Hg(0) from solution into the gas phase
Bibliographic record
Abstract
The objective of this work was to determine the magnitude of mercury isotope fractionation during volatilization of Hg(0) dissolved in aqueous solution to the gas phase and to develop a method for the precise determination of isotope ratios of gaseous Hg(0) by multi-collector ICP-MS. Hg(0) was generated in situ by reducing Hg(II) using SnCl2 and subsequently purged into a trapping solution. A 316 μM KMnO4 trapping solution, acidified by 0.9 M sulfuric acid, recovered 96.1 ± 4.0% of Hg (2 SD, n = 20). The observed δ202Hg of −0.049 ± 0.065‰ (2 SD, n = 17) relative to the initial Hg standard was not greater than the daily external precision of the isotope ratio measurement, which is typically <0.100‰ (2 SD). The volatilization experiments were conducted by reducing Hg(II) completely using SnCl2, letting the developed Hg(0) evaporate from solution and purging the Hg(0) vapor in the headspace over the solution into the trapping solutions. The concentration and isotope ratios of Hg in both the trapping solutions and the Hg(0) remaining in solution were measured at different time intervals. The kinetics of the volatilization was found to be a first order process. The pattern of isotope fractionation during volatilization followed a Rayleigh fractionation with an observed maximum δ202Hg value of 1.48 ± 0.07‰ (2 SD). Fractionation factors of 1.00044 and 1.00047 were obtained in two independent experiments. These results provide the first experimental proof for, and quantified the pattern and magnitude of, the Hg isotope fractionation during volatilization of Hg(0) from solution into the gas phase.
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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".