The mobility of anthropogenic<sup>129</sup>I in a shallow sand aquifer at Sturgeon Falls, Ontario, Canada
Bibliographic record
Abstract
Summary The transport and partitioning of 129 I has been examined for a shallow groundwater flow system at Sturgeon Falls in northeastern Ontario. Recharge into a sandy surficial postglacial deltaic aquifer occurs in the vicinity of a seasonally-wet boreal forest. Concentrations of stable iodine, 129 I, tritium, radiocarbon, stable isotopes and major ions were measured on samples of groundwater and precipitation. The present-day tritium profile delineates the position of the early 1960's above-ground nuclear weapons pulse at a depth of approximately 12 m. The concentrations of stable iodine for groundwaters above, near and below the above-ground nuclear weapons pulse range from 0.07 to 1.7 ppb. Over that same interval 129 I concentrations decreased from 1.9 × 10 6 atoms/L at 9 m, to approximately 1.9 × 10 5 atoms/L in tritium-depleted waters at 35 m, below the present-day depth of the recharging above-ground nuclear weapons peak at approximately 12.7 m. No substantial increases in the levels of 129 I were evident in waters sampled near the location of the above-ground nuclear weapons peak. The 129 I values in the lower aquifer are 1 to 2 orders of magnitude greater than published estimates of pre-bomb 129 I (10 3 to 10 4 atoms/L), and indicate contribution of 129 I from the fissiogenic decay of 238 U in the basal granite bedrock or from leaching of 129 I from the aquifer grains. A precipitation sample collected at Sturgeon Falls had concentrations of stable iodine and 129 I of 0.2 ppb and 8.5 × 10 7 atoms/L, respectively. Concentrations of 129 I in Sturgeon Falls groundwaters are lower than those reported in other studies in central Canada, suggesting that the levels of 129 I in these groundwaters may have been attenuated by complexation or ion exchange with organic materials in the near-surface soil horizons. Such processes have been documented during a previous study on the behavior of 129 I in a shallow aquifer near a low-level, radioactive waste management area. Along a 30 cm soil profile at piezometer nest 28 at the Sturgeon Falls study site, the concentrations of 129 I ranged from approximately 4.3 × 10 8 atoms/g in the uppermost soil litter layer to 5.6 × 10 7 atoms/g in the siltier bottom soil horizons. Over that same profile, stable iodine varied from 4.7 ppm in the upper layers to 3.9 ppm in the lower layers.
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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) | 0.004 | 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".