Phosphorus sorption and desorption characteristics of wetland soils from a subtropical reservoir

Abstract

Water-level regulation results in alternating exposure and inundation of soils in reservoir fluctuation zones, which may significantly influence the phosphorus sorption and desorption processes in the soil. The present study investigated the phosphorus sorption and desorption properties of wetland soils in China's Danjiangkou Reservoir using a batch equilibrium technique. Results showed that the maximum phosphorus sorption ranged from 435 to 1429 mg kg−1, with an average of 771 mg kg−1. The maximum phosphorus sorption was found to be significantly related to amorphous iron (r = 0.883, P < 0.01) and pH (r = −0.333, P < 0.05), and the binding constant k was strongly correlated with the amorphous iron (r = 0.475, P < 0.01) and organic matter (r = −0.455, P < 0.01). The phosphorus desorption percentage varied from 8 to 44%, with a mean value of 24%. The present study implies that short-term inundation in reservoir fluctuation zones would result in soil phosphorus desorption to some extent, in spite of the considerable absorption ability in the exposure period. These results are useful for assessing the phosphorus retention capacity of wetland soils and optimising management strategies for water conservation in reservoir regions.