Evaluation of the sources of nitrogen compounds and their influence on the biological communities in the hyporheic zone of the Sagittario River, Italy: an isotopic and biological approac
Bibliographic record
Abstract
In groundwater-dependent ecosystems (GDEs) a significant contribution of nitrogen contamination of the surface waters arises from groundwater input by shallow and deep flow systems. In general, nitrogen surface-groundwater exchanges and processes at the hyporheic scale are difficult to monitor. In order to have a better understanding about these interactions, it is proposed to use stable isotopes (15N-NO3-, 18O-NO3-, 15N-NH4+) as environmental tracers to identify the sources and fate of the nitrogen compounds in groundwater in the Sagittario River basin, central Italy. The detrimental effect of the groundwater ammonium on the meiofaunal organisms is also evaluated in the hyporheic zone, where N-NH4+ concentrations reach a maximum value of 0.6 mg L-1. The main source of the nitrogen contamination originates from agricultural and urban activities at the catchment scale. The nitrogen compounds reach the gaining stretches of the hyporheic zone along the streambed as nitrate associated to a shallow flow system and ammonium related to a deep flow system. δ15N data demonstrate that sewage and fertilizers including manure are the main sources of NO3- and NH4+, the latter being the major pollutant in the study area. δ18O-NO3- data are consistent with the nitrification of ammonium to nitrate, along with the contribution from inorganic fertilizers. Furthermore, δ15N-NO3- and δ18O-NO3- data reveal that denitrification does not play any role on nitrate attenuation in the shallow aquifer and near the discharge areas to the river. The meiofaunal communities, represented by the Crustacea Copepoda selected as the target group, were shown to be sensitive to the high concentration of ammonium found at several hyporheic sites. The statistical analyses indicated a significant reduction of species abundance in the sites polluted by N-NH4+ concentrations > 0.0653 mg L-1.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".