Phosphorus fractions and phosphate sorption-release characteristics relevant to the soil composition of water-level-fluctuating zone of Three Gorges Reservoir

The phosphorus fractions and phosphate sorption and release characteristics of the surface soil in the water-level-fluctuating zone of Three Gorges Reservoir were investigated. The results indicated that the total phosphorus (TP) contents in the soils varied from 0.39 mg/g to 0.81 mg/g; inorganic phosphorus (IP) was the major fraction of TP; Calcium bound phosphorus (Ca–P) was the main fraction of IP. For all the soils samples, the rank order P-fractions was Ca–P > organic phosphorus (OP) > Phosphorus bound to Al, Fe, and Mn oxides and oxyhydroxides (Fe/Al–P). Phosphate sorption on the sediments was mainly occurred within 2 h and then reached to equilibrium in 12 h. The phosphate sorption rate was closely related to the content of fine particles. The phosphate sorption capacity was ranged from 137.79 mg/kg to 1975.50 mg/kg and the phosphate sorption efficiency was ranged from 47.34 l/kg to 230.88 l/kg; there was no significant correlation between soil compositions and the maximum phosphate sorption capacity, phosphate sorption efficiency. The amounts of phosphate (P) released from the soils were strongly in positive correlations with the contents of Fe/Al–P and OP. It indicated that Fe/Al–P and OP were mainly released fractions, and they can release P easily.

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► We investigate the contents of phosphorus fractions in submerged soils.
► We study the phosphate sorption and release on the soils.
► The rank order P-fractions was Ca–P > OP> Fe/Al–P.
► Phosphate sorption reaches equilibrium in 12 h and Fe/Al–P and OP were main released fractions.