Refinement of the Anion Exchange Membrane Method for Soluble Phosphorus Measurement
- L. R. Cooperband *,
- P. M. Gale and
- N. B. Comerford
The proper use of anion exchange membranes (AEMs) to assess phosphorus availability in situ requires a more thorough understanding of their function under a wide range of soil biophysical conditions. We evaluated the ability of AEMs to sorb selected organic P compounds, determined possible interference of low-molecular-weight organic acids and humic substances on AEM-P sorption, and assessed the efficiency of AEM-P sorption in the presence of wetland sediments and soil-sediment microbes. We collected soils, swamp water, and sediments from a cypress swamp-pine flatwoods ecosystem in north central Florida. Membranes recovered nearly 100% of both ortho and organic P in a study using aqueous solutions of ortho P and organic P compounds. Membrane sorption of ortho P with varying concentrations of oxalate and protocatechuate was close to 100%. There was a reduction of 15 µg P per membrane when AEMs were placed inside low-molecular-weight-cutoff dialysis tubing (<1000 MWCO) in P-spiked swamp water; however, there was no significant tubing effect in non-spiked swamp water. In an experiment exploring effects on AEM-P sorption of P additions to swamp water with or without sediments, AEMs recovered six times more P than measured in non-spiked swamp water with sediments. When swamp water was treated with chloroform, AEMs sorbed an equal or greater amount of ortho P than ortho P measured in swamp water with no AEMs. Results suggest that AEMs can be used to measure soluble and readily desorbable P in low-P status soils and sediments with organic acids.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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