Abstract:

In the hypergene earth system, the chemical weathering is the predominant driving force of a chemical cycle and it affects the compositions of rock, water, soil and atmosphere greatly. Dissolved materials mainly derived from chemical weathering of rocks in river basin, with the combinations of precipitation and the impact of human activities. In this work, the characteristics of chemical compositions of the rivers in Poyang Lake drainage basin and their influencing factors are studied based on the systematic sample collections and chemical composition analysis of river water samples from this area. The results indicate that the Cl-, SO2-4 ion of river water have significantly increased and gradually acidified in the study area in comparison with those in the eighties of the last century. Compared with other main rivers worldwide, the ratios of Ca2+/Na+, Mg2+/Na+, HCO-3/Na+ are lower, which reveal the influences of strong evaporite weathering and human activities. The compositional ionic characteristics of the river water were mainly controlled by rock weathering in the study area, whereas the contribution ratio of precipitation is 10.3% and agricultural activities is 4.9%. The contribution of mining activities to Raohe river ions is 8.9% in wet period while 14.6% in dry season.

Key words: total dissolved solids, major ions, chemical weathering, Poyang Lake Basin