An investigation of chromium and strontium sources in MacAskill Brook Watershed and MacAskill Reservoir, Nova Scotia, Canada: implications for watershed and reservoir management
Bibliographic record
Abstract
This thesis details an integrated paleolimnological—groundwater—soils study in northeastern Cape Breton focussed on identifying the sources of chromium (Cr) and strontium (Sr) within the watershed surrounding a reservoir. The sources of these metals and their pathway into the water in the reservoir is of interest because both metals present a management challenge. The sludge produced as a waste product of water treatment contains elevated Cr, which is an environmental concern and a significant treatment expense. The introduction of freshwater mussels is being considered as a treatment for elevated water colour and because shellfish are known to bioaccumulate Sr. An understanding of the source(s) of Sr is required to determine the environmental implications of this strategy.MacAskill Reservoir is a constructed 329 ha reservoir that drains a 3763 ha watershed and is a potable water source for about 24 000 people. The reservoir watershed is underlain by Carboniferous strata and has been the focus of extensive underground coal mining and surface processing; both coal and marine sediments are considered significant geogenic Sr and potential Cr sources. The overlying glacial till and related soils were generated in part from nearby marine-derived sedimentary strata (sources of Cr and Sr) and nearby ultramafic deposits (source of Cr). Anthropogenic activities in the region (junkyards, coal-powered generation stations, agricultural fields and fertilizers) must also be considered as possible sources of Cr and Sr. To provide as comprehensive an assessment as possible, surface water, groundwater, soils, and paleolimnological samples from a nearby lake and the reservoir were assessed.This study determined that Cr is most prevalent in watershed soils and that Sr appears in the highest concentrations in groundwater. Glacial till underlying the watershed appears to be the primary source of both metals, though local bedrock may also contribute to elevated Sr in water samples. Paleolimnological data indicates that Sr and Cr were probably not transported atmospherically to the site in detectable concentrations. Due to the acidic water and soil in the area, the Cr is reduced in the soil as the stable Cr(III) rather than mobilized in the water column as the more toxic Cr(VI). Cr in the soil is suspected to be elevated because of the glacial till transported from the Boisdale Hills, where mine tailings indicate concentrations greater than 440 mg/kg. Elevated Sr in groundwater is associated with chemical sedimentary rocks in the watershed, particularly the coal-bearing measures that have been mined extensively.The risk of Cr and Sr release into surface and groundwater systems and subsequently into the reservoir can be reduced by limiting landscape disturbances, particularly the wetlands located on the northwestern side of the watershed. Legacy coal workings also have significant potential to release Cr and Sr into water systems and require further assessment and monitoring to better understand the risk. As well, long-term monitoring of the watercourse and reservoir limnology may help determine how seasonality impacts Cr and Sr release into the reservoir.
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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 | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| 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 | 0.000 |
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".