Ecohydrological dynamics of a degrading subarctic peatland: Implications for Arsenic mobility
Bibliographic record
Abstract
A peatland from subarctic Canada (Handle Lake 62°29’26.44”N, 114°23’18.23”W) is a degrading permafrost peatland chosen for detailed study due to a legacy of regional arsenic (As) contamination as a result of almost 8 decades of gold mining. The fate of permafrost peatlands and their element stores is unknown due to complex feedbacks between peat accumulation, hydrology, and vegetation that affect redox state and element mobility. We combine palynology with study of plant macrofossils, testate amoebae, organic matter composition, and bulk geochemistry preserved in a ca. 4180-4972 cal year old peat monolith retrieved from the Handle Lake peatland to reconstruct the ecohydrological dynamics to assess future trajectories of permafrost peat, and contaminant storage or release, in response to current and future warming. Sphagnum riparium macrofossils are rare in modern peat habitats and sub-fossils are rare in paleoecological records. Plant macrofossils of this taxon occur in an 11-cm thick layer together with Sphagnum angustifolium between 43 cm (ca. 3390-3239 cal BP) and 25 cm depth (ca. 2755-2378 cal BP) in the monolith. The S. riparium sub-fossils are present with the hydrophilous testate amoebae species Archerella flavum, Hyalosphenia papilio and Difflugia globulosa that are used to quantitatively reconstruct a water table depth of 0-4 cm below the peat surface. Sub-fossils of S. riparium disappear at ca. 2755-2378 cal BP, likely due to an autogenic trophic shift and succession towards more acidophilic conditions favourable to species such as Sphagnum fuscum and Sphagnum russowii. We interpret the occurrence of S. riparium as an indicator of wet and minerotrophic conditions linked to peatland development form rich fen to oligotrophic bog. Because S. riparium is a key pioneer species of disturbed peatlands that have experienced permafrost degradation it will likely be favoured in northern regions experiencing rapid climate warming. In the palynological record the proportion of Sphagnum-type A spores increases (up to 80%) between ca. 3390-3239 cal BP and ca. 2755-2378 cal BP concurrent with a decline in other Sphagnum-type spores. A peak in micro- and macroscopic charcoal occurs between ca. 3557-3286 cal BP and ca. 3275-2771 cal BP, concurrent with a decline in Picea pollen and an increase in Alnus pollen. Regionally, between ca. 3500 and ca. 2500 cal BP Neoglacial climate prevailed with post-Neoglacial warming at ca. 2500 cal BP. It is therefore possible that regional fire occurrence stimulated permafrost degradation at ca. 3500 cal BP. Background As in the active layer monotlith is ~20-30 ppm. The upper 10 cm of the peat are impacted by aerial deposition of As from ore processing and concentrations range up to ~360 ppm. An increase in the concentration of As in the monolith from ~15-20 ppm at the base of the monolith to ~30-40 ppm during this interval may reflect water table depth dynamics that affected the mobility and fate of this redox sensitive element and/or downward mobility from layers impacted by contamination from mineral processing. Degradation of this permafrost within the Handle Lake peatland will release the currently stored As and other contaminants to the regional environment.
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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 | 0.000 |
| 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".