Chlordane Enantiomers and Temporal Trends of Chlordane Isomers in Arctic Air
Bibliographic record
Abstract
A 14-year data set (1984-1998) for chlordane compounds in arctic airwas examined to discern temporal trends. trans-Chlordane (TC), cis-chlordane (CC), and trans-nonachlor (TN) declined significantly (p < 0.001-0.02), with apparent times for 50% reduction of 4.9-9.7 y. The isomer fraction of TC = (TC/(TC + CC) also declined significantly (p < 0.001 -0.014) over the same time period. The enantiomeric composition of TC and CC was determined in air samples collected at arctic stations in Canada (1993-1996), Russia (1994), and Finland (1998), and a temperate station on the Swedish west coast (1998). Enantiomer fractions, EF = (+)/[(+) + (-)], were significantly different from measured EFs of racemic standards (0.498-0.501) at all stations for TC (p < 0.001) and two stations for CC (p < 0.001 to <0.05). These observations suggest changing source composition of chlordane in arctic air, with a greater proportion of weathered residues in recent years, possibly derived from soils. Identification of nonracemic (mean EFs = 0.662-0.703) heptachlor exo-epoxide (HEPX) at the four air stations further exemplifies contributions of soil emissions to long-range transport of chlordane-related compounds.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| 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) | 0.000 | 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".