Mathematical model of phosphate release rate from sediments considering the effect of dissolved oxygen in overlying water

Abstract

A quantative model of phosphate release rate from sediment considering the effect of DO in overlying water was developed and compared with the experimental data. The model considered the diffusion, adsorption and desorption of phosphate; the diffusion, oxygenation and hydroxide formation of ferrous iron; and the bacterial oxygen consumption. The phosphate release flux was obtained as a linear decreasing function of DO in the overlying water. The critical concentration of DO in the overlying water at which the phosphate release is stopped was expressed as a function of the thickness of the oxygenation layer which depends on the ferrous iron oxygenation rate constant, the bacterial oxygen consumption rate constant and the ferrous iron diffusion coefficient. The prediction by the present model when the bacterial oxygen consumption rate was small, was favorably compared with the observed data in Lake Teganuma.