Characteristics of Phosphorus Fractions in Different Sediments of River, Pond and Constructed Wetlands in North of China

In order to better understand phosphorus (P) cycling in wetland ecosystem, the characteristics of phosphorus fractions in sediments of Heituwa construction wetland system were investigated using soil organic phosphorus (Po) fractionation scheme. For seven sediments, total phosphorus (TP) varied from 531.9 to 1177.3 mg kg^-1 and inorganic phosphorus (Pi) was the main P fraction which accounting for 88.5 to 95.6% of TP, the concentrations of Po in different sediments changes significantly in contrast to Pi, the maximum is more than five times the minimum, The concentrations of TP, Pi and Po in sediments were all decreased from Yongding river to stabilization pond and to the inlets of the surface flow constructed wetlands, but increased along the wetland flow directions, it suggests that wetland mineral soils had a greater P retention capacity than organic soils and wetlands act as P (especially Pi) sinks during growing season, The content of Po in sediments has a approximately value in September and November but all Po fractions except labile Po showed significant seasonal variations, it indicates a significant Po cyclic process within the organic phosphorus fractions, There were significant and positive correlations between OM with TP, Pi, Po and P fractions except moderately labile Po, OM and P biogeochemical cycles were closely associated in sediments. This study indicates that the Po in sediment play an importance role in wetland ecosystem and suggested more attention should be paid to Po in further research and management of constructed wetlands.