Mass absorption cross-section of ambient black carbon aerosols - a review
Bibliographic record
Abstract
Abstract An accurate assessment of black carbon (BC) climate and health impacts requires knowledge of its mass absorption cross-section (MAC BC ) – a parameter linking optical and mass measurements. The mean MAC BC for freshly emitted soot typically spans a narrow range of 8 ± 1 m 2 g⁻ 1 at 550 nm 1,2 but is modified by subsequent atmospheric aging. Determination of MAC BC requires simultaneous measurements of aerosol light-absorption coefficient ( β abs ) and BC mass. Here, we compile 230 measured MAC BC values from 80 atmospheric studies and explore the effects of sampling location, study duration, instrumentation, and measurement wavelength. The compiled data set shows a broad variability in MAC BC values (a factor of about 200%). We conclude that this variability is attributable to a combination of the above-mentioned effects with additional instrumental uncertainties (e.g., cross-sensitivities and/or inadequate instrument calibration). The current state of knowledge does not support the use of simplistic generalizations or assumptions about MAC BC in the atmosphere, motivating a recommendation to further improve and standardize measurement practices.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.004 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".