Phosphorus Bioavailability and Speciation dynamics within fluvial suspended sediments
Bibliographic record
Abstract
Eutrophication of agricultural catchment streams remains a global problem despite increasingly stringent regulations. Long term, sustained release of bioavailable phosphorus (P) from legacy P stored in fluvial sediments may impact downstream water quality, hence greater understanding is required regarding P speciation dynamics and potential release mechanisms from fluvial sediments to the water column.This study examined the dynamic P fractions, speciation and bioavailability of suspended fluvial sediments from two geologically contrasting agricultural catchment streams (Ballyboughal (BB) and Tintern Abbey (TTA)) using a combination of complimentary techniques including sequential chemical fractionations (SCF), Dual Culture Diffusion Apparatus mesocosm experiments (DCDA), X-ray fluorescence spectroscopy (XRF) and X-ray Absorption Near-edge Structure (XANES) spectroscopy. Results from the SCF of fluvial suspended sediments pre- and post DCDA microcosm experiment’s revealed that loosely bound P (PH2O), exchangeable P against OH– ions (PNaOH), and organic P (POrg) are the major P fraction contributors to the bioavailable P fraction which would promote algal growth. Other P fractions including acid-soluble P principally associated with calcium phosphate compounds (PHCl) and ferric bound P (PCBD) showed relatively lower mineralisation to bioavailable P. Significantly, P K-edge XANES spectra enabled identification of seasonal and spatial P speciation dynamics and the existence of major P fractions including Fe-P and Ca-P associated mineral phases along with organic P compounds. Additionally, SCF, XRF and Ca K-edge XANES show contrasting Ca associated phases between both catchments, with calcite dominant in the BB sediments and Ca humic-complexes predominant in the TTA sediments. Contrasting Ca-P fraction transformation mechanisms of the two catchments are indicated by P redistributions in SCF and the reduction of elemental Ca amounts from XRF analysis. Calcium (Ca) K-edge XANES shows the BB catchment has a large amount of calcite while TTA was shown to contain organic Ca compounds, likely in the form of Ca-humic-complexes. This study provides a conjunctive method for future studies and validation of P speciation and bioavailability assessment associated with fluvial suspended sediments from agricultural catchments streams. The results contribute to future catchment scale sedimentary fluvial P modelling and enhanced catchment management strategies to improved water quality.
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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 | 0.001 | 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".