Use of Geochemical Forensics to Determine Release Eras of Petrochemicals to Groundwater, Whitehorse, Yukon
Bibliographic record
Abstract
At sites where petrochemical releases have occurred comparatively recently (i.e., over the last 20 years), explicit age-dating is a viable approach. However, differentiating among multiparty contamination at sites with several decades of history may mandate a different allocation strategy, especially when there is an uncoordinated body of environmental data. At a location where a refinery operated for 11 months during World War II, and which has been used as a fuel distribution terminal over the ensuing 60 years, regulatory interest was triggered in 1997 when a sheen was detected discharging into the adjacent Yukon River. Our investigation combined disparate forensic tools with data visualization software to establish the sources and extent of nine distinct groundwater plumes/product areas and to estimate their periods of release. Plumes were spatially identified based on solute distribution. Earliest Demonstrable Inception Date (EDID) and Latest Possible Initiation Date (LPID) were determined based on petrochemical additives: lead and its derivatives (MTEL, TEL, and TML); MTBE, TAME, and MMT; isotopic (13C/12C) and n-C17:pristane ratios; SIM DIS curves; and aerial photography. Of these, aerial photography and additive history proved the best attribution methods to identify the EDID/LPID. This approach appears to be a useful tool when there is a long history of releases, but caution is necessary in interpreting potentially mixed plumes from different eras.
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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 | 0.002 | 0.002 |
| 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".