Application of Dendrochronological and Dendrochemical Methods for Dating Contamination Events of the Saint-François and Massawippi Riverbanks (Québec, Canada)
Bibliographic record
Abstract
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. Keywords: contaminated soildendrochemistrydendrochronologyheavy metalhydrocarbonriverbank Acknowledgements The authors would like to thank all the individuals and organizations that contributed to this study, including the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Fond Institutionnel de Recherche (FIR-UQTR) for their financial support. We would like to acknowledge the Geological Commission of Canada (GCC-Québec) and INRS-ETE laboratory's support for the dendrochronology and dendrochemistry analyses. We would like to also acknowledge the reviewers for the constructive comments that helped to improve the manuscript. Lastly, we would like to extend our warm thanks to Luc Lavoie, François Péloquin, and Marc Laurencelle for their valuable assistance during field works and Francis Baril for his help for figures and maps. Notes Lead alkyls, in particular added to gasoline for their antiknock properties, were withdrawn in the USA in 1975, while the reduction of the lead content in gasoline began in Europe in the mid-1980s, and later, prohibition measures were adopted collectively by the European directives in the late 1990s (Directives Auto/Oil 98/69 and 98/70 of the European Parliament). In France, Germany, and other European countries, unleaded gasoline was first officially put on the market in 1990. In Canada, the lead content in gasoline was reduced in the 1980s (CitationBollhöfer and Rosman, 2001) and gasoline with lead was removed from the market for good in 1990 (CitationCEPA, 1990). *Tree sample used for replicate; **Values of soil profile samples. *Soils with hydrocarbon contaminant levels ranging from 300 to 700 mg/kg fall within Class B and have usage restrictions (CitationMDDEP, 2002). *The numbers in bold indicate the level of soil contamination in B Class (CitationMDDEP, 2002). The values obtained for PAHs and PCBs analysis are not included in the table. (i) Notes: Articles in regional newspaper (La Tribune) mentioning two cases of contamination on the Saint-François River in 1955 and 1963. "La rivière Saint-François, polluée sur une distance de 45 milles." La Tribune, Sherbrooke, 25 octobre 1955. "La rivière Saint-François est couverte de grandes mares d'huile—Origine inconnue." La Tribune, Sherbrooke, 17 mai 1963.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".