| Non-point source pollution (NPSP) has been become one of the most important environmental focuses recently. The pollutants, such as municipal solid waster (MSW), fertilizers, pesticides, heavy metal, and so on, which can do harmful to human' physical health straightly, enter into water environment, so could accuse eutrophication pollution and other negative effect. Eutrophication pollution will cause alga propagation in excess, so that fish and water plant will die largely. And the aquatic ecosystem will be destroyed severely and lose the normal functions of zoology. The routines, by which the pollutants transfer from land to water environment, are various. Precipitation runoff, subsurface water infiltrating, nitrogen forms letting straight, all can put pollutants into water environment. NPSP has many characteristics, contrast with point source pollution. For instance, indeterminacy of time, way and quantity brought much difficulty to the management of NPSP. Randomicity, universality, space-time variability and harm potentiality, all are the characteristics of polluting process. So the control measures to NPSP are more complex than to point source pollution.As the cadency of controlling point source faster, the more important role the NPSP acting on the management of water environment. More pollutants were brought into rivers and lakes through NPSP than point source pollution did in the world, China included. The quality of drinking water resource is being menaced dominatingly by NPSP in many cities in China. And this phenomenon is becoming more outstanding than ever. Quantities of studies have been done in this field. Many effective control measures were listed for NPSP. However, there are still many differentiae among all kinds of effect factors in different areas, which results in investigating in concrete place under the necessity.This paper takes the Three Gorge Reservoir Areas (TGRA) as target to study NPSP. The reason lies on the important status and the contaminate position in this area. With the construction step accelerating of Three-Gorge Project and the reservoir commencing sluice, it is the urgent affairs to protect the environment and ecosystem in the TGRA. The quality and security of the reservoir is closely linked with region environmental conditions. Only if the reservoir runs in gear, can the dam maintain working safely. Lots of municipal construction was set up in order to decrease pollutants output, such as landfill sites, sewage disposal plants, and so on, The economic measures and law lever also were introduced into the battle against pollution. As a result, point source pollutants are dropped off dramatically and these wasters' fatalness because feebleness accordingly. However, because of the pollution characteristics, the management for NPSP is much difficulty and the quantity of pollutants can not be diminished easily in TGRA. Recently, the current velocity are cut down 2/3 contrast with that of before sluice. Water quality study points out the content of variouspollutants have added on a large scale. Parts of the whole water area reach the level of eutrofication, and the concentration of heavy metal exceeds the environmental criteria vastly. NPSP has given rise to a series of negative effect to this region's ecosystem. The results of environmental monitoring have demonstrated much more it is important to control non-point source pollutants.Due to the influence of various factors, NPSP is characterized by random process, complex mechanism. According the progress of research in TGRA, several factors can affect NPSP, including gross of pollutants, competency of environmental self-purification, terrain and physiognomy, soil and vegetation, climate and hydrology, land use method, farming activity and the level of farm management. Such factors either influencing the pollution source or contaminate process would be changed by human, the main body of environment. So the environmental ideology status for inhabitants should be a kind of macroscopical factor. Strictly speaking...
|
PDF Full Text Request