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Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading
Published on: March 6, 2014
Colloidal and dissolved phosphorus in sandy soils as affected by phosphorus saturation
Katrin Ilg1, Jan Siemens, Martin Kaupenjohann
1Department of Soil Science, Institute of Ecology, Berlin University of Technology, Salzufer 11-12, D-10587 Berlin, Germany. katrin.ilg@tu-berlin.de
Journal of Environmental Quality
|April 22, 2005
Summary
Excess phosphorus (P) in soils increases dissolved and colloidal P concentrations, raising concerns for water quality. Critical levels of phosphorus saturation (DPS) were identified, indicating a risk of P release into drainage systems.
Area of Science:
- Soil Science
- Environmental Chemistry
- Agronomy
Background:
- Fertilization exceeding crop needs leads to phosphorus (P) accumulation in soils.
- This accumulation can increase dissolved and colloidal P concentrations in soil drainage.
- Understanding phosphorus release mechanisms is crucial for managing water quality.
Purpose of the Study:
- To determine if increasing degrees of phosphorus saturation (DPS) elevate dissolved and colloidal P concentrations.
- To identify critical DPS levels associated with P release from soils.
- To investigate factors influencing colloidal P mobilization.
Main Methods:
- Soils (Typic Haplorthods) from four fertilization experiments were analyzed.
- Oxalate-extractable P, iron (Fe), and aluminum (Al) quantified DPS.
- Dissolved and colloidal P, Fe, Al, and carbon (C) measured in water and KCl extracts.
- Turbidity and zeta potential assessed colloidal properties.
Main Results:
- Dissolved P concentrations increased sharply at DPS > 0.1.
- Colloidal P concentrations rose with increasing DPS due to colloid mobilization and increased P content.
- In subsoils, 94% of water-extractable P was bound to colloids.
- Ionic strength and Ca(2+) influenced colloidal P release, with KCl extraction showing a stronger DPS-colloidal P relationship than water extraction.
Conclusions:
- Soil phosphorus accumulation increases both dissolved and colloidal P concentrations.
- There is a significant risk of colloidal P mobilization from soils with high DPS.
- Colloidal P, dominant in subsoil drainage, can be released from soils with relatively low DPS, posing a threat to water bodies.
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