PENG Haixia1, LIU Longhai1,2, TAO Zhen1, LV Xiaoxi1, LI Shanchi1,3, DENG Haojun1, GAO Quanzhou1,4,*
(1. School of Geography and Planning, and Guangdong Provincial Key Laboratory for Urbanization and Geo-simulation, Sun Yat-sen University, Guangzhou 510275, China;
2. Guangzhou Baiyun District Water Authority, 510405, China;
3. Guangzhou Institute of Forestry and Landscape Architecture, 510405, China;
4. Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Exploration，Guangzhou 510275, China)
Abstract: The Xizhijiang River Basin (XRB), a silicate rock dominated basin in South China, was selected to study the relationship between chemical weathering and riverine hydrochemical compositions of small and medium rivers in the humid subtropical mountainous area. The water samples from the main stream and the tributaries were collected in January and July 2011 and analyzed. The graphic method and the forward model were used to analyze and calculate the hydrochemical compositions in the XRB. The results showed that the main cation and anion in runoffs of the XRB were Na+ and HCO3-, respectively, both accounted for more than 55% of total ions. The chemical weathering of silicate was the most important source (45.8%), followed by the human activity (24.7%) and the chemical weathering of carbonate (22.0%), the contribution from atmospheric input to cations was relatively small (7.5%). The seasonal variation of the hydrochemical compositions was significant for tributaries influenced by carbonate chemical weathering and human activities, while the seasonal variation was not significant for tributaries influenced by the silicate chemical weathering. Silicate and carbonate chemical weathering rates in the XRB were 8.27 t/(km2？a) and 56.95 t/(km2？a), respectively, and the CO2 consumption rates were 0.80×105 mol/(km2？a) and 8.52×105 mol/(km2？a), respectively.
Key words: chemical weathering; hydrochemical compositions; source of ions; seasonal variation; the Xizhijaing River Basin
EARTH AND ENVIRONMENT Vol.46, No.6, Tot No.326, 2018, Page 513-523
