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Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment
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Microbially Induced Soil Colloidal Phosphorus Mobilization Under Anoxic Conditions
Kamel M Eltohamy1,2, Daniel Menezes-Blackburn3, Erwin Klumpp4
1Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
Environmental Science & Technology
|April 22, 2024
Summary
Anoxic conditions significantly increase colloidal phosphorus (Pcoll) in soils, transforming small particles into larger aggregates. Microbial activity, particularly fungi, drives this release, enhancing phosphorus mobility and transport into floodwaters.
Area of Science:
- Soil Science
- Environmental Chemistry
- Microbiology
Background:
- Colloidal phosphorus (Pcoll) dynamics are critical for understanding soil nutrient cycling and water quality.
- Anoxic conditions, common in flooded soils, can significantly alter phosphorus speciation and mobility.
- Previous research has focused less on the specific behavior of Pcoll under fluctuating redox conditions.
Purpose of the Study:
- To investigate the behavior and transformation of colloidal phosphorus (Pcoll) in acidic floodplain soil under induced anoxic conditions.
- To quantify the changes in Pcoll size distribution and aggregation during a simulated flooding event.
- To elucidate the role of microbial communities in Pcoll mobilization and transport.
Main Methods:
- Incubation of acidic floodplain soil under controlled oxic and anoxic conditions for 30 days.
- Measurement of pore-water colloidal phosphorus (Pcoll) concentrations and size fractions using advanced analytical techniques.
- Analysis of colloidal morphology and aggregation using electron microscopy.
- Microbial community analysis via 16S rRNA and ITS sequencing to identify key players in Pcoll dynamics.
Main Results:
- A rapid shift from oxic to anoxic conditions caused a significant increase in pore-water Pcoll, exceeding soluble P by over 2.7-fold.
- Colloidal fractions shifted from dispersed (<220 nm) to aggregated forms (>220 nm), indicating enhanced aggregation under anoxia.
- Electron microscopy confirmed the transformation of dispersed colloids into larger, aggregated particles.
- Microbial activity, with a notable contribution from fungi over bacteria, was identified as the primary driver of anoxia-induced Pcoll release and aggregation.
Conclusions:
- Anoxia profoundly impacts colloidal phosphorus (Pcoll) behavior in soils, leading to increased concentrations and aggregation.
- Microbial communities, especially fungi, play a crucial role in mediating Pcoll mobilization and transport under flooded conditions.
- These microbially-driven changes in Pcoll dynamics have significant implications for phosphorus release from soils into aquatic ecosystems.
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