Carbonaceous species in PM <sub>2.5</sub> at a pair of rural-urban sites in Beijing, 2005–2008
Bibliographic record
Abstract
Abstract. One-week integrated PM2.5 samples were collected at a pair of rural (MY)-urban (TH) sites in Beijing over four years between 2005 and 2008. Weekly OC and EC in PM2.5 were compared to investigate their respective levels and temporal patterns at the two sites, and differences in the factors contributing to them were discussed. A systematic decrease of annual mean concentration of OC and an opposite trend for EC at both sites, and the significantly lower fractions of TCM (total carbonaceous mass) in PM2.5 mass than those measured at TH in 1999, indicate that the relative importance of carbonaceous species in PM2.5 was probably weakened whereas that of EC in TC was steadily enhanced. Clear seasonal variations were found for both OC and EC concentrations (varying seasonally by factors of 1.35~3.0) at TH with higher weekly concentrations and fluctuations in winter and much lower values in summer and spring. The minimum seasonal urban excesses of OC (3.0 μg m−3) and EC (1.2 μg m−3), which were only one-ninth to one-eighth of their corresponding maxima, both occurred in 2008 summer. The noticeably more positive stable carbon isotope values (δ13C) of EC at TH in that summer relative to the preceding summers puts in new evidence that the contribution to carbonaceous particles from mobile sources was substantially reduced due to a concerted effort to reduce emissions from new and existing vehicles before, during and after the Summer Olympics. No consistent seasonal patterns of OC and EC concentrations without strong correlations and their high ratios (OC/EC) at the MY site reflect their complex and variable major sources and formation/production in the rural area compared to the urban area in Beijing, such as biomass burning during the harvest seasons, widely used high-polluting family stoves and small boiler for cooking and heating, and high potential formation of SOA.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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".