Experimental research on the effect of water velocity on phosphorus release from sediments of a plateau cold water type river

Abstract

The release of phosphorus from sediment is an important source of endogenous phosphorus in water bodies and is an important factor affecting the total phosphorus content in river system. Water velocity is key factor affecting the rate of phosphorus release from sediments. In this paper, the effects of water velocity on the release of phosphorus from sediments in a plateau cold water type river were investigated. The ecological environment of plateau cold water rivers is sensitive and fragile. The changes in environmental conditions can easily lead to changes in the overall water quality of rivers. Therefore, exploring the release process of phosphorus in plateau cold water rivers under changes in hydrodynamic conditions is important for protecting the ecological environment of plateau rivers. The results showed that the release of total phosphorus from sediments followed a first-order kinetic process, when the flow velocity was lower than the threshold velocity of sediments. The total phosphorus release coefficient of sediment linearly increased with increases in water flow velocity. The total phosphorus release coefficient of sediment was related to the flow velocity by k_TP20=3.03v/v_c+0.08v<v_c at 20 °C. The release equilibrium concentration of total phosphorus from the sediment was increased with the increase of velocity. The relationship between the balance concentration of total phosphorus release and water velocity was expressed as C_s20=0.10v/v_c+0.04v<v_c at 20 °C. The results could provide a quantitative basis for the source term expression of phosphorus release kinetics in the mathematical model of phosphorus transport in the plateau cold water type river.

Keywords: Phosphorus release; Plateau river; Release coefficient; Sediment; Water velocity.