Using N and O isotope fractionation for evaluating denitrification in aquatic systems
Bibliographic record
Abstract
ABSTRACT The increasing prevalence of nitrate contamination in surface waters, groundwater, and ocean waters, represents a critical environmental challenge, particularly in regions with intensive agriculture and aquaculture. Denitrification, the microbial reduction of nitrate to dinitrogen gas, plays a pivotal role in mitigating this contamination and regulating the global nitrogen cycle. Stable isotope analysis provides critical insights into nitrate transformation pathways, distinguishing denitrification from anaerobic ammonium oxidation (anammox), another N-loss process, or internal recycling processes such as dissimilatory nitrate reduction to ammonium (DNRA). This review highlights the importance of isotopic tools for assessing nitrate attenuation in natural and anthropogenic-impacted systems and explores the use of nitrogen (δ 15 N) and oxygen (δ 18 O) isotopic fractionation to trace denitrification and to quantify its extent in diverse aquatic environments. The nitrogen (N) and oxygen (O) isotopic fractionation during denitrification is evaluated at organism and ecosystem levels. Also, environmental factors modulating isotopic composition of N compounds in groundwater, rivers, lakes, riparian zones, coastal wetlands and oxygen-deficient marine regions are explored. Advances in isotope biogeochemistry and analytical techniques improve our ability to assess the transport and fate of nitrate, integrating isotopic data with hydrological and biogeochemical models. A precise characterization of N and O isotopic enrichment factors for denitrification supports improved predictions of nitrogen cycling dynamics under changing environmental conditions. These approaches enhance understanding of nitrogen removal processes and help refine estimates of nitrogen fluxes at local, regional and global scales. By providing a quantitative framework for evaluating denitrification and related processes, this review contributes to developing more effective strategies for managing nitrogen pollution and mitigating its impacts on aquatic ecosystems.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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".