| Abstract: | Dissolved and particulate, organic and inorganic N, P and Si weremeasured in the main stream and 15 major tributaries of the Changjiang (YangtzeRiver) in April–May 1997. The nutrient concentrations are related towaterdischarge, suspended particulate matter, anthropogenic activities etc. Thenutrient levels were quite low in the upper reaches, and significantlyincreasedin the main stream in a region of 2000–3000 km inland from the rivermouth. The northern tributaries contribute more nutrients to the Changjiangthanthe southern tributaries. Based on atomic ratios of N, P and Si, the limitingnutrient in the Changjiang drainage basin was P. The nutrient yields in theChangjiang and its major tributaries indicated high rates of transport ofnutrients within the watersheds. Concentrations of nitrate in the Changjianghave increased, but there have been no systematic trends for phosphate andsilicic acid since 1980. The DIN/P ratios and DIN/Si ratios increased. TheDIN/Pand DIN/Si ratios may be expected to continue to increase after construction ofthe  Three Gorges Dam , which will exercise a great deal ofinfluence on theecological environment of the Changjiang estuary and its adjacent sea. |
