[Characteristics of phosphorus sorption on Yellow River sediments from Inner Mongolia reach]

Sorption behavior of phosphorus on sediment samples taken from Inner Mongolia reach of the Yellow River in 6 different geographical sites was determined in laboratory, and the correlation between chemical-physical properties of the sediments and their phosphorus sorption characteristics was analyzed. The maximum sorption capacities were 43.64-85.46 mg/kg. The zero equilibrium P concentration (EPC0) of the sediments ranged from 0.0003 to 0.0198 mg/L, 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. Sediments from Shizuishan, Wulateqianqi and Qingshuihe along the Yellow River were sources of phosphorus, while sediments from Wuhai, Linhe and Baotou cross sections were sinks of phosphorus, at the typical P concentrations of the river water. However, both the sorption and desorption capacities were low at the conditions tested here. The Langmuir sorption constant (k) was positively correlated to the cation exchange capacity (CEC), organic matter and clay mineral content, but negatively correlated to the particle size of the sediments. The maximum sorption capacity of phosphorus was remarkably correlated to the active Fe content. Active Fe played a key role in holding phosphorus on the sediments.