黄河沉积物对磷的吸附行为

研究了黄河流域9个沉积物对磷的吸附行为,用修改后的Langmuir等温吸附模型对吸附实验数据进行了拟合,得到最大吸附容量PAC、Langmuir吸附平衡常数k.利用所得拟合参数通过公式计算方法得到EPC_0,以此判断沉积物是磷"源"还是磷"汇",分析了沉积物组成及其理化性质与磷吸附特征的关系.结果表明,各沉积物的吸附,解吸平衡磷浓度EPC_0范围在0.0031～0.109 3 mg/L,,其值也较低,与可解吸的内源磷含量正相关,与地理位置没有表现出相关性.在本研究条件下,在壶口张家湾断面,沉积物对磷表现为"汇";而其他沉积物对磷表现为"源",但释放量和吸附量不大.黄河沉积物对磷的最大吸附容量PAC的范围为0.073～0.454 mg/L,吸附能力较弱,沉积物的最大吸附容量与沉积物的有机质有较好的正相关关系.此外,沉积物对磷的吸附存在明显的固体浓度C_S效应,吸附滞后角随着C_S的增加而增大,随着同体浓度的增加,沉积物对P的吸附量逐渐降低,但EPCC_0值却增大,体现了颗粒物在磷循环中的两性作用.

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(EPC_0) 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 EPC_0 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(C_s) effect exists obviously in P adsorption experiment and the hysteresis and EPC_0 became bigger as C_s increased.