Atmospheric Aerosol over Vermont: Chemical Composition and Sources
Bibliographic record
Abstract
Aerosol chemical composition data for PM2.5 samples collected during the period from 1988 to 1995 at Underhill, VT, were analyzed. Sulfur and black carbon mass concentrations ranged from 0.01 to 6.5 microg m(-3) and from 0.05 to 2.2 microg m(-3), respectively, while the total fine aerosol mass concentration ranged from 0.2 to 51.1 microg m(-3). Seasonal variations with maxima during the summer and minima in winter/spring were observed for sulfur and the fine mass concentrations. No annual pattern was observed for black carbon. Seasonal variations for most of the other anthropogenic species had maxima in winter and spring and minima in the summer. A factor analysis method, positive matrix factorization (PMF), utilizing error estimates of the data to provide optimum data point scaling was used to obtain information about possible sources of the aerosol. An 11-factor solution was obtained. The six sources representing wood burning, coal and oil combustion, coal combustion emissions plus photochemical sulfate production, metal production plus municipal waste incineration, and emissions from motor vehicles were identified. Emissions from smelting of nonferrous metal ores, arsenic smelting, and soil particles and particles with high concentrations of Na were also identified by PMF. Potential source contribution function (PSCF) analysis combines the aerosol data with the air parcel backward trajectories. PSCF was applied to identify possible source areas and pathways that give rise to the observed high particulate mass concentrations from these 11 sources. The CAPITA Monte Carlo trajectory model was used to obtain 10 sets of 5-day air parcel back trajectories arriving every 2 h for the 7-yr period from 1988 to 1995. The PSCF plot for the black carbon factor shows high probabilities in the area surrounding the sampling site, indicating a strong local influence from residential wood combustion in northern New England and southwestern Quebec. Similar large potential source areas in the midwestern United States were identified for the two coal combustion factors. The midwestern United States was also identified as the source region for the Zn-Pb factor. The oil combustion factor was associated with the east coast of the United States. The results for the Pb-Mn factor suggests high probability over the nearby Montreal urban area and the areas in the midwestern United States. The windblown dust emissions from the areas to the north are significant contributors for the soil factor. Canadian Ni smelters are the main sources for the As factor, although there is some contribution from coal-fired power plants to the south and west of Underhill, VT. It is concluded that the combination of the two receptor modeling methods, PMF and PSCF, provides an effective way in identifying atmospheric aerosol sources and their likely locations. Emissions from different anthropogenic activities as well as secondary aerosol production are the main sources of aerosol measured in Vermont. Fuel combustion, local wood smoke, municipal waste incineration, and the secondary sulfate production collectively accounted for about 87% of the fine mass concentrations measured in Vermont.
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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 | 0.001 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".