Behavior of phosphorus adsorption on the Yellow River sediments

Adsorption behavior of phorsphorus on Yellow River sediments was determined in laboratory. The modified Langmuir isotherm equation was used to describe phosphate (P) sorption on the Yellow River sediments. The maximum P sorption capacity (PAC) and P-binding energy constant (k) were obtained by the modified Langmuir isotherm model. The zero equilibrium P concentration (EPC0) was subsequently calculated by the corresponding formulae, which was used to predict whether bed sediments are acting as a source or sink of soluble reactive phosphate.The correlation between chemical-physical properties of the sediments and their phosphorus characteristics was analyzed. The EPC0 of the sediments ranged from 0.003 1 to 0.109 3 mg·L-1,which was positively correlated to the contents of native adsorbed P (NAP). The sediments played a dual role of sink and source of P at different geographical sites. Sediment from Hukou and Zhangjiawan were sinks of phosphorus, while other sediments were sources of the river water. However, both the sorption and desorption capacities were low at the conditions tested here. The NAP was linearly related to the contents of organic matter in sediment. In addition, solid concentration (Cs) effect exists obviously in P adsorption experiment and the hysteresis and EPC0 became bigger as Cs increased.