Compound‐specific hydrogen isotope analysis of 1,2‐dichloroethane: potential for delineating source and fate of chlorinated hydrocarbon contaminants in groundwater
Bibliographic record
Abstract
Abstract A Delta Plus XL continuous flow gas chromatography/high‐temperature conversion‐isotope ratio mass spectrometer system (GC‐TC‐IRMS) with a liquid nitrogen trap installed at the end of the micropyrolysis oven was used to measure hydrogen isotope ( δ 2 H) values of 1,2‐dichloroethane (1,2‐DCA). The 1,2‐DCA δ 2 H values were within uncertainty of the δ 2 H value for the same 1,2‐DCA analyzed using off‐line sample preparation and conventional dual inlet mass spectrometry, verifying that this system can accurately measure 1,2‐DCA δ 2 H values. After 71 reproducible and accurate 1,2‐DCA δ 2 H measurements had been obtained, the standard deviation on the mean of the cumulative 1,2‐DCA δ 2 H measurements was greater than ±5‰. The cumulative load of chlorine at this point was ∼5.5 × 10 −6 moles, which may be the limit to the quantity of chlorine that can be input before the reproducibility of 1,2‐DCA δ 2 H measurements is compromised. This study is the first to our knowledge to demonstrate a method for obtaining accurate and reproducible compound‐specific δ 2 H values for chlorinated hydrocarbons at dissolved concentrations typical of field conditions. Paired δ 2 H and δ 13 C values suggest that dual parameter isotopic measurements can distinguish between different contaminant sources, as well as providing additional constraints on degradation pathways and contaminant remediation. Copyright © 2007 John Wiley & Sons, Ltd.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 teacher head, 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".