Effects of pH and salinity on phosphorus sorption and desorption in the surface sediments of the mainstream of the Haihe River

Phosphorus speciation analysis using sequential extracting methods was combined with phosphorus sorption and desorption experiments to understand the effects of pH and salinity on phosphorus sorption and desorption in the surface sediments of the Haihe River.The results showed that Ca-P and Re-P were the two main fractions of P in the surface sediment of the mainstream of the Haihe River.A modified Langmuir isotherm fitted the phosphorus sorption well(R2 0.90),and the sorption capacity of sediments from eight locations of Haihe River mainstream were high,which indicated that the Haihe River mainstream sediments will be a source of phosphorus in the future.The pH effect on phosphorus sorption from sediments was U-shaped,so phosphorus desorption from sediments increased with pH,due to displacement of PO3-4 adsorbed on sediment surfaces by OH-.Phosphorus sorption decreased with increasing salinity,and phosphorus desorption decreased with increasing salinity,resulting from stronger anion competition.