Effects of various ion solutions on phosphorus adsorption in the sediments of a water body that originated from agricultural land subsidence and submergence caused by coal mining activities

Extensive subsidence and submergence of agricultural land has been caused by coal mining activities in the Huainan Coal Mine Area, China. Considering the site-specific regional water chemistry, we investigated the influence of ion solutions on phosphorus (P) adsorption behavior in the sediments of a 20-year-old body of water. The P isothermal adsorption was measured in four different types of ion solutions, prepared through additions of sodium chloride (NaCl), calcium chloride (CaCl2), sodium bicarbonate (NaHCO3), a mixture of sodium bicarbonate and calcium chloride (NaHCO3 + CaCl2), and ultra pure water (deionized water with specific resistivity reaching the value of 18 M Omega cm) as a control. The sediments parameters analyzed included P-fractions, organic matter (OM), iron oxides, clay, and others, with the aim of analyzing their individual effects on P adsorption. Cationic calcium (Ca2+) was to found to enhance P adsorption ability, while a weakly alkaline environment (simulated through NaHCO3 addition) reduced it. The effects of ion solutions on P adsorption potential were in the order CaCl2 > NaHCO3 + CaCl2 > NaCl > ultra pure water > NaHCO3. The two-dimensional structure of lake sediments overlying inundated agricultural soil could be responsible for the observed differences between sediment properties and P adsorption features in different layers of sediments.