Application of Dendrochronological and Dendrochemical Methods for Dating Contamination Events of the Saint-François and Massawippi Riverbanks (Québec, Canada)
Bibliographic record
Abstract
Soils contaminated with hydrocarbons and others contaminants (heavy metals, PCBs, PAHs) were recently discovered in the banks of the Saint-François and Massawippi rivers. The aim of this study is to attempt to date the contamination events using dendrochronological and dendrochemical methods. For this study, dendrochronology is used to indicate the age of trees, identify the morphological growth anomalies, and provide the geochemical profile timeframe, with dendrochemistry used specifically to identify metal element concentrations in the growth rings of the selected specimens. Sampling for the two types of analysis was done on the banks of the Saint-François River in Windsor and Richmond, where the level of hydrocarbon contamination in the soil profiles is among the highest. Core samples were taken from three red ash (Fraxinus pennsylvanica Marsh.) and dendrochemical analyses were done on the tree rings (191 samples). Dendrochemistry was successfully used to determine that there were heavy metals in the rings, and also to estimate the date of the contamination events by using tree-ring wood. Several contamination events were identified through the presence of lead and other metal trace elements (As, Cd, Cu, Ni, and Zn) in the xylem of the trees analyzed at the selected sites. This suggests that various contaminants were transported by the river on several occasions and deposited on floodplains during successive floods. The atmospheric fallout must also be considered as the other source of pollutants recorded in the trees.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 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".