Sequential Extraction of Metal Contaminated Soils with Radiochemical Assessment of Readsorption Effects
Bibliographic record
Abstract
The operational speciation of selected trace metals in several contaminated Toronto area soils was determined by a modified BCR (Community Bureau of Reference) sequential extraction procedure. This type of environmental analysis is now increasingly used, but its reliability is questioned due to concerns regarding redistribution of extracted metals occurring during the procedure. Using radiotracer techniques, the redistribution of Cd and Zn during the sequential extraction was directly quantified. For a fill material taken from downtown Toronto, metal partitioning behavior conformed with the theory and anecdotal evidence in the soil chemistry literature: Cd was highly mobile, while Cu and Pb were primarily associated with oxidizable organic matter, and Zn was distributed across all soil fractions. Soil from an abandoned metals recycling operation had unusual physical characteristics, and the trace metals within were largely nonextractable. In the soils examined, some 20−30% of the Cd and Zn released from the acid-soluble fraction of the soil was readsorbed to the reducible mineral oxide fraction. The extent of the phenomenon is less than previously suspected and does not invalidate sequential extraction results for these metals.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".