Characterization of the Effects of Redox Condition on Fe(III)/Fe(II) Transformation in a Small Karstic Aquifer: Poocher Swamp Freshwater Lens, South Australia
Bibliographic record
Abstract
The presence of iron in potable water supply aquifers poses a major water quality problem and may render the supply unsuitable for domestic or industrial uses, unless appropriate treatments is undertaken. Evaluation of redox conditions in groundwater is a prerequisite for studies involving Fe(III)/Fe(II) transformation in aquifers. This study characterizes the redox conditions, geochemical evolution and distribution of iron in a small karstic freshwater aquifer, the Poocher Swamp freshwater lens, located in south-east of South Australia. The freshwater lens is formed as a result of flows from Tatiara Creek that enter Poocher Swamp and recharge the aquifer through two sinkholes located in the northwest section of the swamp. Stable isotopes of water molecules, δ2H and δ18O, indicate that both Tatiara Creek and Poocher Swamp waters are isotopically more enriched due to evaporation than the pristine water of the aquifer. The Na+/Cl- ion ratio >0.85 for Tatiara Creek, Poocher Swamp and wells within the lens suggest additional sodium source(s) are involved in the evolution of groundwater chemistry. This study use redox potential, dissolved oxygen (DO) and dissolved organic carbon (DOC) contents to describe Fe(III)/Fe(II) transformation in the groundwater, and relate this to iron distribution within the lens. Three distinct redox zones are present in the freshwater lens; anoxic zone up to one kilometre from Poocher Swamp where dissolved oxygen (DO) is <1 mg.L-1, redox potential (Eh) <100 mV, and iron (Fe) in groundwater 2.3-9.3 mgL-1. Following the anoxic zone is the suboxic zone (from 1to1.5 km from Poocher Swamp), where DO is <1 mg.L-1, Eh is about 110-275 mV and Fe is 0.4-0.6 mg.L-1. The oxic zone is 1.5 to 2.3 km from Poocher Swamp and is characterized by high DO (2-4 mg.L-1), higher Eh (>300 mV) and low in Fe (<0.015 mg.L-1). Only 0.4 km2 of the 13 km2 area of the freshwater lens is oxygenated, thus limiting further developments of the lens as potable water supply source.
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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 | 0.000 | 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) | 0.001 | 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".