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Updated: May 27, 2025
06:42
Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment
Published on: July 22, 2019
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A conceptual model for dissolved P mobilization from legacy sources.
D M Nash1,2, R W Mc Dowell3,4, P J A Kleinman5
1School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, Australia.
Journal of Environmental Quality
|February 20, 2025
Summary
Agricultural phosphorus runoff is a problem. This study models dissolved phosphorus mobilization, suggesting current P indices need updates to better manage water quality, especially on low slopes.
Area of Science:
- Environmental Science
- Soil Science
- Water Resource Management
Background:
- Excessive phosphorus (P) in freshwater limits resource amenity, particularly in agricultural catchments.
- P fertilizers and manure increase soil fertility but contribute to P exports.
- Current P indices aim to reduce P exports but impacts on receiving waters are inconsistent.
Purpose of the Study:
- Propose a model for dissolved P mobilization in surface runoff.
- Examine modifications to P indices to better accommodate dissolved P.
- Address the inconsistency between P export declines and water quality improvements.
Main Methods:
- Developed a two-phase model of dissolved P mobilization (entrainment) in surface runoff.
- Analyzed P mobilization via dissolution, advection, diffusion, and hydrodynamic dispersion.
- Validated the model using runoff monitoring data under natural and simulated rainfall.
Main Results:
- Dissolved P mobilization occurs in two phases: initial dissolution/advection, followed by diffusion/dispersion.
- The second phase, occurring after labile P is depleted, is responsible for most dissolved P exports.
- Low-slope areas, with prolonged soil-water interaction, exhibit higher dissolved P concentrations.
- Current P indices do not adequately represent dissolved P mobilization from low-slope areas.
Conclusions:
- A mechanistic model of dissolved P mobilization is proposed, accounting for two mobilization phases.
- Existing P indices require modification for improved dissolved P management, especially on low slopes.
- Enhanced P indices should incorporate greater mechanistic complexity and compartmentalization while retaining usability.
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