[Phosphorus sorption capacities of the pond sediments in a headstream agricultural watershed].

The land uses in watersheds have important influence on the sediments of lakes and wetlands. Field and laboratory experiments were conducted to research the phosphorus adsorption by the pond sediments in the pond system in a headstream watershed. Being scattered in different ambient land uses and receiving soil particles from various sources, the pond system provides an excellent research example for the phosphorus sorption characteristics. It was found that the pond sediments had strong phosphorus sorption capacities. The phosphorus adsorption maximum (Smax) ranged from 228 to 974 mg x kg(-1), equilibrium phosphorus concentration (EPC0) ranged from 0.004 to 0.032mg L(-1). The mean degree of phosphorus saturation (DPS) of the pond sediments was only 9.5%. The situation of the ponds can influence the physico-chemical properties of sediments and their sorption characteristics. For Smax, Hill pond >Nonirrigation pond> Rice pond> River pond> Village pond. On the contrary, for EPC0, Hill pond< Nonirrigation pond< Rice pond < River pond < Village pond. The phosphorus adsorption maximum (Smax) was significantly correlated ly correlated with the KCl-extractable phosphorus (KCl-P, r2 = 0.83, p < 0.001). Multiple regression analysis shows that Fe(ox) and KCl-P are the key factors, which can influence phosphorus sorption of the pond sediments.