Defining the sources and evolution of nitrate in coal mine rock with stable isotopes of nitrate and ammonium
Bibliographic record
Abstract
Elevated concentrations of nitrate (NO 3 ˉ) are present in many surface waters associated with coal mining throughout the world. Its presence is generally attributed to blasting using ANFO (NH 4 NO 3 and fuel oil) to access the coal. A recent study conducted by our group shows the nitrification of naturally occurring exchangeable ammonium (NH 4 + -ex) in waste rock can be a major source of NO 3 − compared to contributions from NO 3 − and the nitrification of NH 4 + originating from blast products. Here we show that neither the concentrations of nitrogen species nor the δ 15 N-NO 3 − and δ 15 N-NH 4 + values can be used to differentiate the sources of NO 3 − . However, the measured δ 18 O-NO 3 ˉ values of NH 4 NO 3 (+24.3±1.7 ‰) and NO 3 ˉ produced from nitrification of both sources of NH 4 + (-4.7 ‰) under oxic laboratory conditions enabled the distinction between these two sources of NO 3 ˉ. Fitting the results of a simple mixing model to the experimental data allowed the concentrations of NO 3 ˉ derived from NH 4 NO 3 in fresh-blasted mine rock to be estimated. The results of this study show the application of δ 18 O-NO 3 ˉ is a valuable technique to characterize the source(s) and evolution of NO 3 − draining from mine rock piles. • Nitrate in mine rock is often attributed to blasting using ammonium nitrate • Nitrification of geogenic ammonium is major source of nitrate in coal mine rock • The nitrogen-15 isotopes cannot be used to differentiate the sources of nitrate. • Oxygen-18 isotopes of nitrate can be used to differentiate between sources of nitrate • Nitrate concentrations from potential sources can be estimated using a mixing model
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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".