Analysis on the present situation of water environment in the Changjiang estuary

The present situation and distribution characteristics of water quality in the Changjiang estuary is analyzed using the W value method, according to the hydrological and water quality data measured during the comprehensive harnessment and development plan of the Changjiang estuary at the end of 2002. It shows that the water quality of the Changjiang estuary generally reaches the third water quality standard, while the water quality in some specific sections is in the fourth or fifth water quality standard. Quite a few water quality parameters are above the standard in various degrees. The main pollutants are TN, COD_(Mn), total lead, chlorine ion, oil, and so on. It also indicates that the water quality of the northern branch is worse than that of the southern branch, northern harbor and southern harbor, and the water quality of the southern bank of the southern branch is worse than that of the northern bank. The water quality of sections in urban areas is worse than that in rural areas. The water quality seems better in high-tide period than in low-tide period, in riffles than in pools, and upstream than downstream. The pollutants affecting the water quality include organic and inorganic matter. The pollution sources include domestic ones and industrial ones, static ones and mobile ones, and pointed ones and non-pointed ones. The pollutants can be taken into the estuary along with the runoff or tidal flows.