Using Aeration to Enhance Phosphorus Adsorption and Immobilization by the Sediment and LMB
2020
Song, Xiaojun | Li, Dapeng | Xu, Chutian | Huang, Yong
Dissolved oxygen (DO) in the overlying water is important in influencing internal phosphorus (P) release. However, the potentially associative effect of DO on the P adsorption and immobilization by La-modified bentonite (LMB) has not been quantified. This 80-day incubation experiment showed the synergistic effect of DO and LMB in the overlying water, which caused the reduction of dissolved inorganic phosphorus (DIP) by 51% (DO = 5 mg L⁻¹) and 77% (DO = 7 mg L⁻¹) on average, respectively, compared with the DO of 3 mg L⁻¹. In addition, the DIP in the pore water decreased from 1.12 mg P L⁻¹ (control) to 0.014 mg P L⁻¹ (5 mg L⁻¹) and 0.004 mg P L⁻¹ (7 mg L⁻¹). Besides, the Fe²⁺ and NH₄⁺ concentrations were also reduced significantly in the pore water, suggesting the rise in the redox potential in the sediment, which helped P immobilization. Chemical P-fractionation experiments indicate that the Fe-P reduction in sediment was the most significant, reduced by 14%, followed by NH₄Cl-P (12%), causing a reduction by 13% (3 mg L⁻¹), 23% (5 mg L⁻¹) and 27% (7 mg L⁻¹) of mobile P in the surface 7-cm sediment, respectively. However, the released P ions were rapidly adsorbed by the Al ions and Ca ions, as well as their compounds, thereby leading to the obvious rise in inert P in the sediment. Accordingly, it was suggested that DO and LMB had a synergistic effect on external P adsorption and immobilization.
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