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 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) | 0.000 | 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 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".