Sedimentological and limnological evolution of recreational lakes in a former asbestos mining region (Québec, Canada): insights from paleolimnology
Bibliographic record
Abstract
The Bécancour River basin in southern Québec (Canada) has been impacted by more than a hundred years of asbestos mining activities in the Thetford Mines region. Several recreational water bodies located downstream from the city are suffering from high sediment and contaminant loads and eutrophication. In order to prepare an efficient management of the fluvial lakes, we completed paleolimnological investigations to evaluate the extent of their deterioration and identify catchment disturbances that influenced their present-day condition. Here we present the results of a multi-proxy study of sediment cores collected from a chain of 5 lakes. The sedimentary records from these lakes indicate severe perturbations associated with the complete draining of Lac Noir, a former lake near Thetford Mines excavated and drained for mining purposes between 1955-1959. Radiometric 210Pb dating revealed extreme increases in the sediment accumulation rate following this event. Analyses of loss-on-ignition, carbon (C) and nitrogen (N) isotopes, grain-size, and X-ray microfluorescence indicated that the post-1960 sediments were enriched in fine-grained mineral matter and had higher metal and nutrient concentrations as compared to older sediments at the bottom of the cores. Changes in the δ13C and C/N ratios and the predominance of diatom taxa (class Bacillariophyceae) typical of nutrient-rich waters (e.g., Cyclostephanos invisitatus, Cyclotella meneghiniana) also showed that the 1955-1959 event led to a rapid eutrophication of some lakes. Results from our study illustrate that the asbestos mining activities had dramatic impacts on lake biota and contaminant levels, and suggest that major restoration efforts will be needed to improve their ecological condition.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".