Anthracene Photodegradation Kinetics in Salty Aqueous and Organic Solutions
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide The reactivity of organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) in environmental condensed phases depends strongly on matrix composition. Pollutants such as PAHs are often associated with atmospheric aerosols, so an understanding of the effects of changing aerosol composition is required to accurately predict their environmental chemical fate. We have measured the photodegradation kinetics of the PAH anthracene in aqueous solutions containing sodium or potassium chloride (NaCl or KCl) at chloride concentrations greater than those observed in seawater (0.56 M) but relevant to environmental matrices such as atmospheric aerosols, industrial brines, and saline wastewater. At concentrations greater than 0.56 M but below the saturation limit (4.6 M for KCl, 6.1 M for NaCl), the rate constant did not depend on Cl – concentration, but rather remained relatively constant at a value approximately a factor of 2 greater than the rate constant measured in deionized water. We attribute this behavior to competition between a heavy atom effect that suppresses photodegradation by promoting intersystem crossing from anthracene’s excited triplet state to its singlet ground state, and the salting out effect, which we demonstrate increases photodegradation by promoting anthracene self-association. At KCl and NaCl concentrations exceeding the saturation limit, the photodegradation rate constant increased with increasing salt concentration. This is hypothesized to be due to anthracene-NaCl(s) interactions. This is supported by observed monotonic increases in anthracene’s photodegradation rate constant in octanol containing up to 1.5 M solid NaCl. The results suggest that the fate of anthracene, and potentially other aromatic pollutants, in high-salt environments may not be accurately predicted by reaction mechanisms and kinetics from existing literature, which is based almost exclusively on measurements performed in low-salt (seawater concentrations and lower) conditions.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".