XU Zhi-fang¹ , TANG Yang ^{2, 3}
( 1. Key Laboratory of Engineering Geomechanics , Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 
2.State Key Laboratory of Environmental Geochemistry , Institute of Geochemistry , Chinese Academy of Sciences , Guiyang 550002, China; 3. Graduate School of Chinese Academy of Sciences , Beijing 100049, China )

Abstract: The upper Hanjiang River basin is the water source area of the Middle Route of South to North Water Transfer Project of China. The chemical and strontium isotopic composit ions of the river water are determined with a main purpose t o underst and the chemical weathering processes and anthropogenic influences. The ionic composition of river waters is characterized by dominance of Ca²⁺, HCO₃^-, and followed by Mg²⁺ and SO₄^2-. Analyses of the stoichiometry of the river water show that the water chemistry is controlled by carbonate dissolution. High concent rations of major anions ( Cl^- , NO₃^-,  and SO₄^2-) are ascribed to both extensive influences from agriculture and domestic activities over the drainage basin. Chemical and Sr isotopic compositions ( ⁸⁷Sr/ ⁸⁶Sr) of river water indicate that at least three major reservoirs ( silicate, limestone and dolomite) contribute to the dissolved loads. The chemical weathering rates are estimated to be around 38. 6 and 4. 4 t/ km2/ a for carbonates and silicates, respectively, and the total chemical weathering rate is higher than the global mean value.

Key words: South to north water transfer project ; water source area; hydrogeochemistry; chemical weathering

*Corresponding Author, E-Mail: zfxu@mail.iggcas.ac.cn

Bulletin of Mineralogy, Petrology and Geochemistry Vol. 30, No.1, 2011, page 26-30

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