『Abstract
　The Xijiang River, the mainstream of the Zhujiang (Pearl) River, which is the second largest river in China in terms of discharge, flows through a large carbonate rock region in South China. The chemical and Sr isotopic compositions of the Xijiang waters were determined during the high-flow season in order to understand the chemical weathering processes, associated CO2 consumption and anthropogenic influences within the carbonate-dominated basin. The major ion compositions of the river waters are characterized by the dominance of Ca²⁺, Mg²⁺, HCO3^- and are significantly rich in SO4^2-. The SO4^2- is mainly derived from the oxidation of sulfide minerals and acid precipitation caused by coal combustion. Chemical and Sr isotopic compositions of the river waters indicate that four reservoirs (carbonates, silicates, evaporites and anthropogenic inputs) contribute to the total dissolved loads. The chemical weathering rates of carbonates and silicates for the Xijiang basin are estimated to be approximately 78.5 and 7.45 ton km^-2a^-1, respectively. The total chemical weathering rate of rocks for the Xijiang basin is approximately 86.1 ton km^-2a^-1 or 42 mm ka^-1, which is much higher than global mean values. The budgets of CO2 consumption by carbonate and silicate weathering are estimated to be 284×10⁹ and 54.3×10⁹ mol a^-1, respectively. It would appear that H2SO4 is involved as a proton donor in weathering reactions in the Xijiang basin; calculated results show that the contribution of cations from rock weathering induced by H2SO4 accounts for approximately 11.2％. Results from this study show that the flux of CO2 released into the atmosphere is approximately 0.1×10⁶ mol C km^-2a^-1 or 0.41×10¹² g C a^-1 produced by H2SO4-induced carbonate weathering in the basin. When extrapolated to the entire surface area of carbonate in SW China, the flux of CO2 released to the atmosphere by H2SO4-induced carbonate weathering is about 1.41×10¹² g C a^-1.』

1. Introduction
2. Natural setting of the Xijiang drainage basin
　2.1. Geography and geology
　2.2. Climate, land cover, and human activities
3. Sampling strategies and analytical methods
4. Results
　4.1. Major elements
　4.2. Strontium concentrations and isotopes
5. Discussion
　5.1. Sources of solutes
　　5.1.1. Atmospheric inputs of sea-originating solutes
　　5.1.2. Anthropogenic inputs
　　5.1.3. Rock weathering inputs
　5.2. Chemical budget and chemical weathering rate estimation
　5.3. Sulfuric acid as weathering agent
6. Conclusions
Acknowledgments
References