This paper presents a theoretical analysis of a pulsed bicomponent contaminant emission into a free-surface wetland flow.The basic equations are for the bicomponent contaminant transport in the wetland flow under the combined action of advection,mass dispersion,and ecological reaction at the phase averaged scale.The effect of the ecological reaction is separated from the hydro-dynamic effect via a set of widely used transforms.The analytical solution for the evolution of the depth-averaged concentration is rigorously derived,with a limiting case covering the known solution for the single component contaminant transport.It is found that the depth-averaged species concentration of the bicomponent contaminant can approach an equilibrium state determined by the distri-bution coefficient.
Previous studies on river health evaluation mainly focused on characterizations at a river-corridor scale and ignored the complex interactions between the river ecosystem and other components of the river basin.Based on the consideration of the interactions among rivers,associated river basin and habitats,an assessment framework with multi-scale indicators was developed.An index system divided among these three scales to characterize the health of river ecosystems in China’s Liao River Basin was established.Set pair analysis was applied to integrate the multi-scale indicators and determine the health classes.The evaluation results indicated that the rivers in the western and eastern zones of the Liao River were classified as sick,and rivers in the main stream of the Liao and Huntai rivers were classified as unhealthy.An excessive level of disturbances,such as large pollution loads and dense construction of water conservation projects within the river basin,were the main causes of the river health deterioration.
