The effects of drying on phosphorus sorption and speciation in subtropical river sediments
Bibliographic record
Abstract
The present study investigated whether drying and desiccation substantially increase the biologically available phosphorus (P) in riverbed sediments from a dry subtropical river. Sequential extraction and batch equilibrium experiments were undertaken on sediments with contrasting organic matter content, percentage fines and P content. The response of sediments to drying differed predominately as a result of drying time rather than as a result of the different physiochemical properties and total P content of the sediments. For both in situ and laboratory drying, major changes in P speciation occurred in the surface-layer sediment (0–2 cm) where NH4Cl-P (loosely sorbed P) was higher in partially dried and desiccated sediments than in wet sediments. Conversely, NaOH-nrP (labile organic and poly-P) was significantly lower (P < 0.05) in partially dried and desiccated sediments than in wet sediments, suggesting that a substantial transformation from a relatively unavailable organic form to a readily available inorganic form of P had occurred with drying. The equilibrium phosphate concentration (EPC0), which is a measure of the potential for sediments to function as a source or a sink of phosphate (PO43–), was higher in sediments desiccated in situ and in the laboratory than in submerged and partially dried sediments. Together with the speciation results, the higher EPC0 indicates that the potential for sediments to release P during the next flow event is substantially increased as a result of desiccation. The lower EPC0 in partially dried sediments suggested that the degree of drying may be an important factor in terms of the long-term potential for sediments to act as a source or a sink of PO43– after rewetting. The results from the present study have important implications because natural or anthropogenic processes which lead to riverbed drying may increase the flux of bioavailable P from bed sediments when flow returns.
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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".