Characteristics of Water Quality in the Changjiang River: Observations Conducted in 1998 and 1999
长江干流主要营养盐含量的变化特征——1998~1999年日中合作调查结果分析

In order to better understand the biogeochemical process of the Changjiang (Yangtze) River and pollutant load flowed into the East China Sea from the river and provide scientific basis for eco-environmental and water resources protection, field surveys along the Changjiang River from Chongqing to Shanghai (about 2300 km long) were carried out in autumns of 1998 and 1999 through the international cooperative study between the National Institute for Environmental Studies (NIES), Japan and the Changjiang Water Resources Commission, China. In this paper, the preliminary results of water quality conducted in the joint survey were presented. From the concentration variations of SS, DOC, T-P, NH 4 -N, NO 3 -N and DT-N along the main course of the Changjiang River during both surveys of 1998 and 1999, it is evident that the concentrations of SS and nutrients in the autumn of 1999 were higher than that in the summer of 1998, because the influence of non-point pollutant source and the discharge and water level during the survey period in 1999 was much higher than that in 1998. On the other hand, the general tendency of the nutrient distribution increased from upstream to downstream along the main course of the Changjiang; the concentrations of nutrients were evidently higher in the downstream of big cities than that in the upstream of these big cities. Water quality was improved after passing through the Gezhouba Dam. It was also found that the BOD and NH 4 -N concentrations increased sharply after passing Dongting and Poyang lakes.