Bibliographic record
Abstract
The significance of vadose-zone biodegradation on the vapor intrusion of petroleum compounds is well recognized, but considered to a limited extent in the guidance document. Although exceptions can occur, the likelihood that dissolved hydrocarbons in groundwater will cause impacts to indoor air is remote. It is more reasonable to focus screening efforts on hydrocarbon release sites with i) shallow NAPL present below the building, ii) direct contact of dissolved hydrocarbons on the building, or iii) migration of petroleum vapors through preferential pathways in contact with contamination. Studies have demonstrated that vadose-zone aerobic biodegradation of petroleum hydrocarbons is common and significant (Roggemans et al., 2001). The USEPA vapor intrusion database and industry experience both indicate that dissolved petroleum hydrocarbons in groundwater do not cause vapor intrusion impacts. Provided no preferential pathways are present, the potential for biodegradation is increased at sites with low hydrocarbon concentration, large depth to source, relatively permeable soils, and no capping effect (e.g., low permeability surface soil or cover that would limit transport of O2 into the subsurface) (Health Canada, 2004). Hence, Health Canada is currently considering a provision to allow for a 10x adjustment in the attenuation factor to account for biodegradation at sites with no surface cap and large depths to source. Modeling and site investigation studies demonstrate that biodegradation can result in many orders of magnitude reduction in vapor intrusion risk estimates (Abreu and Johnson, 2005b; Ettinger
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.004 | 0.002 |
| Insufficient payload (model declined to judge) | 0.897 | 0.836 |
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; the direct Gemma label and the distilled Codex classifier agree on what is shown here.
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".