Isotopic characterization of nitrate, ammonium and sulfate in stack PM2.5 emissions in the Athabasca Oil Sands Region, Alberta, Canada
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Bibliographic record
Abstract
Stable isotope techniques may be a suitable tool for tracing industrial emissions in the atmosphere and the environment provided that the isotopic compositions of industrial emissions are distinct. We determined the isotopic compositions of nitrate, ammonium and sulfate in PM<sub>2.5</sub> emitted from two industrial stacks at a large upgrader site in the Athabasca oil sands region (AOSR), northeastern Alberta, Canada, and compared them to the nitrogen and sulfur isotopic compositions of source materials and upgrading by-products. We found distinct isotopic compositions of nitrate and ammonium in PM<sub>2.5</sub> compared to those reported for atmospheric nitrate and ammonium in the literature. Nitrate in PM<sub>2.5</sub> had δ<sup>15</sup>N values of 9.4‰ (Stack A) and 16.1 ± 1.2‰ (Stack B) that were significantly enriched in <sup>15</sup>N compared to the feedstock materials (∼2.5‰), by-products of upgrading (−0.3–1.3‰), and atmospheric N<sub>2</sub> (0‰). δ<sup>15</sup>N of ammonium in PM<sub>2.5</sub> showed a large range with values between − 4.5 to +20.1‰ (Stack B). We report the first measurements of the triple oxygen isotopic composition of industrial emitted nitrate. Nitrate emitted as PM<sub>2.5</sub> is not mass-independently enriched in <sup>17</sup>O resulting in Δ<sup>17</sup>O = 0.5 ± 0.9‰ (Stack B) and is therefore distinct from atmospheric nitrate, constituting an excellent indicator of industrial derived nitrate. δ<sup>18</sup>O values of nitrate in PM<sub>2.5</sub> (36.0 and 17.6 ± 1.8‰ for Stack A and B, respectively) were also significantly lower than δ<sup>18</sup>O values of atmospheric nitrates and hence isotopically distinct. δ<sup>34</sup>S values of sulfate in PM<sub>2.5</sub> were with 7.3 ± 0.3‰ (Stack A) and 9.4 ± 2.0‰ (Stack B) slightly enriched in <sup>34</sup>S compared to δ<sup>34</sup>S in bitumen (4.3 ± 0.3‰) and coke (3.9 ± 0.2‰). δ<sup>18</sup>O values of sulfate in PM<sub>2.5</sub> were 18.9 ± 2.9‰ and 14.2 ± 2.8‰ for Stack A and Stack B, respectively. The isotopic composition of sulfate in PM<sub>2.5</sub> was not sufficiently different from δ<sup>34</sup>S and δ<sup>18</sup>O values of sulfate in long-range atmospheric deposition in industrial countries to serve as a quantitative indicator for industrial emitted PM<sub>2.5</sub>. We conclude that δ<sup>18</sup>O and Δ<sup>17</sup>O values of nitrate in stack-emitted PM<sub>2.5</sub> are excellent, and δ<sup>15</sup>N values of nitrate and ammonium are suitable indicators for identifying and tracing of PM<sub>2.5</sub> nitrate and ammonium emitted from two stacks in the AOSR in the surrounding terrestrial and aquatic ecosystems.
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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 it