Abstract:

The chemistry of major elements (Ca，K，Na，Mg，Cl-，SO2-4 and alkalinity) from the Changjiang River was examined with data obtained from the main stream and its main tributaries in April 2003.HCO-3 was the most abundant anion of the Changjiang River and account for 60%~90% of total anion，concentrations of anions follows the order HCO-3>SO2-4>Cl-.Among the cations，Ca2+ was predominant and account for 40%~80% of total cation.Concentrations of cations vary in the order Ca2+>Na+>Mg2+>K+.Weathering and erosion were primary importance in affecting river chemistry，which accelerated by anthropogenic activities (e.g.farming).According to the principal composition analysis of river water，water chemistry was mainly controlled by the dissolution of calcite.Silicate weathering played a minor role in the contribution to the river fluxes，while atmosphere input of major elements to the Changjiang River was very limited.The result showed that the dissolved load of the Changjiang River relative to water discharge and in absolute terms was very high compared with other major rivers in the world.High levels of major elements were often observed in rivers in temperate climate zones，whereas rivers in tropical climate zones had abundant water discharge，but relatively low levels of major elements.

Key words: Changjiang River/ major elements/ concentration/distribution