Intercomparison of Clean Air Status and Trends Network Nitrate and Nitric Acid Measurements with Data from Other Monitoring Programs
Bibliographic record
Abstract
The U.S. Environmental Protection Agency Clean Air Status and Trends Network (CASTNET) utilizes an open-face filter pack system to measure concentrations of atmospheric sulfur and nitrogen species. Concentration data for nitrogen species measured with filter pack systems sometimes deviate from data collected by other measurement systems used to measure the same species. The nature of these differences suggests that more than one sampling mechanism or atmospheric process is involved. The study presented here examines these differences by intercomparing CASTNET data with data from other studies, examining the results from earlier intercomparison studies, and conducting a field test to investigate the effect of particle size on filter pack measurement systems. Measurements of nitrogen species from the Maryland Aerosol Research and Characterization (MARCH) monitoring site were compared with nitrogen concentrations at three nearby CASTNET sites. Results indicate that CASTNET measured higher particulate nitrate (NO3 -) and lower gaseous nitric acid (HNO3) concentrations. Comparisons of NO3 - from 34 collocated CASTNET and Inter-agency Monitoring of Protected Visual Environments (IMPROVE) sites show that CASTNET NO3 - measurements were typically higher than the corresponding IM PROVE values. Also, results from the Lake Michigan Air Director’s Consortium Midwest Ammonia Monitoring Project demonstrated NO3 - dissociation on Teflon filters. To investigate the effect of particle size, filter pack measurement systems were operated at three CASTNET sites with and without cyclones during six 7-day measurement periods from March to August 2006. Results indicate the size-selection cyclones had a significant effect on both NO3 - and HNO3 concentrations, but little effect on sulfate (SO4 2-) and ammonium (NH4 +) levels. NO3 - concentrations sampled with the open-face filters were significantly higher than concentrations measured with a 2.5-μm cut point, as were HNO3 concentrations. Although limited in spatial and temporal coverage, the field study showed that the use of an open-face filter pack may allow for the collection of coarse NO3 - particles and for the reaction of HNO3 with metals/salts on the Teflon filter.
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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 | 0.003 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".