Regulators of Phosphorus Retention and Release

Abiotic phosphorus retention by wetland soils is regulated by various physicochemical properties including pH, redox potential, iron, aluminum, and calcium content of soils, organic matter content, phosphorus loading, and ambient phosphorus content of soils. 

FIGURE 9,33 Relationship between oxalate-extractable iron and aluminum and phosphate sorption maximum of mineral wetland soils. (Adapted from Reddy et al., 1995.) 

FIGURE 9.34 Relationship between oxalate-extractable aluminum and phosphate sorption in mineral and peat-based wetlands. (Adapted from Richardson, 1985.) 

FIGURE 9.35 Influence of Eh and pH on phosphorus solubility in mineral wetland soil. (Adapted from Patrick et ah, 1973.) 

Under alkaline conditions, reduction of FeP04 occurs and P released potentially reacts with Ca + forming CaHP04. Similarly, Fe + reacts with COf and precipitates as FeCOj. 

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