Abstract:

To study the responses of isothermal adsorption and desorption of phosphorus at sediment surface to oxygen-consuming organic matters, the sediments sampled from Jinhai Bay of Weihai City were used as materials. The glucose represented the oxygen-consuming organic matters. Sediments were exposed to oxygen-consuming organic matters with different concentrations for 30 hours and the apparent isothermal adsorption capacity of phosphate at the sediment surface were determined and analyzed. Without exogenous PO₄-P, the apparent isothermal adsorption capacity of phosphate at the sediment surface was negative, -2.31±0.63, -42.70±0.98, -7.84±0.83, -3.54±0.39 mg/kg respectively when the concentrations of oxygen-consuming organic matters were 0.00, 0.20, 0.40, 0.80 mg/L. With exogenous PO₄-P, the apparent isothermal adsorption capacity of phosphate varied between positive and negative. The apparent isothermal adsorption capacity of phosphate at the sediment surface under the same concentration of oxygen-consuming organic matters was -5.47±13.90, -13.29±0.97, -13.85±4.36, -0.44±6.44 mg/kg respectively when the initial concentration of phosphate was 2.26 mg/L. The apparent isothermal adsorption capacity of phosphate at the sediment surface under the same concentration of oxygen-consuming organic matters was -59.74±7.33, 28.51±29.28, 87.72±48.19, -30.70±31.52 mg/kg respectively when the initial concentration of phosphate was 6.78 mg/L. The apparent isothermal adsorption capacity of phosphate at the sediment surface under the same concentration of oxygen-consuming organic matters was -13.15±12.17, -7.57±21.09, -55.05±2.79, 87.38±107.33 mg/kg respectively when the initial concentration of phosphate was 9.04 mg/L. The apparent isothermal adsorption capacity of phosphate at the sediment surface under the same concentration of oxygen-consuming organic matters was 67.62±12.80, 257.53±51.72, 122.08±138.24, 201.67±105.42 mg/kg respectively when the initial concentration of phosphate was 11.30 mg/L. Thus, organic matters have double effects on adsorption and desorption of phosphate at sediment surface with exogenous PO₄-P, and the effects depend on the concentration of oxygen-consuming organic matters and the initial concentration of PO₄-P.

Key words: sediment, phosphorus, oxygen-consumed organic matters, adsorption, desorption