| The middle and upper reaches of Wenyu River was chosen as a case study area, and the temp-spatial difference of surface water quality was systematically studied by water sampling from June to August of 2009. It was found that distinct seasonal variations was exhibited on surface water quality in the study area. In the mountain regions, TP, TN, NO-3-N, NH+4-N and TOC concentration in the water increase from June to July, and then decline remarkably, whereas the DO and COD concentration in the water display an opposite pattern. However, in the piedmont plains of Wenyu River middle reaches, TN, TP, PO3-4-P and COD concentration decrease sharply from June to July and then increase substantially in August, while DO concentration shows a decline tendency from June to August. Furthermore, from the upper stream mountains to middle reaches of Wenyu river, self-purification capacity of surface water is reduced with its nutrient pollution aggravates, and the water pollution process and its formation mechanism are different. Altogether, the process of water pollution in the mountainous areas has a pulse pollution process in the rainy season, and the surface run-off in the rainy season may aggravate the pollution process by bring a large volume of non-point source pollutants into surface water from the land. Because of various types of pollution sources in the piedmont regions, the water pollution processes are unstable and peak surface run-offs in the rainy season may dilute the surface water pollutions. The results provide a scientific basis for ecological function regionalization. |
