Characteristics of water chemistry and its indication of chemical weathering in Jinshajiang, Lancangjiang and Nujiang drainage basins

• DOI: 10.1007/s12665-015-5115-y
• Publication Date: 2016-03-18T22:04:30Z
• Authors: Li-Li Zhang; Zhi-Qi Zhao; Wei Zhang; Zheng-Hua Tao; Lu Huang; Jun-Xiong Yang; Qi-Xin Wu; Cong-Qiang Liu
• Keywords: 13. Climate action; 15. Life on land; 01 natural sciences; 6. Clean water; 0105 earth and related environmental sciences

We present major ion compositions for water samples from Jinshajiang, Lancangjiang, and Nujiang drainage basins of China, collected in a water-rich period. This was done to determine natural chemical weathering rates on the eastern Himalayan and Qinghai-Tibet Plateau (HQTP), where anthropogenic impacts are considered small. The major ion distribution of the mainstream samples primarily reflects the weathering of carbonates, which accounts for ~46 % of total cations in the samples of Lancangjiang and Nujiang. Evaporite dissolution prevailed in the mainstream samples of Jinshajiang, as evidenced by high total dissolved solids (TDS) (364–479 mg/L) and Cl, SO4, and Na-dominant major element composition. Silicate weathering contributed <16 % of total cations TDS in the studied rivers. Some samples of the Nujiang near the Tengchong Volcano showed distinctive silicate weathering signatures. Chemical erosion rates of carbonate were 22.5 and 42.7 t km−2 a−1 at Lancangjiang and Nujiang, respectively. At Jinshajiang, evaporite dissolution was important, with a weathering rate 29.5 t km−2 a−1. The contributions of silicate weathering to total dissolved materials were minor, with weathering rates of 1.8, 2.2, and 5.1 t km−2 a−1 at Jinshajiang, Lancangjiang, and Nujiang, respectively. Net CO2 consumption by silicate weathering was 96 × 103 mol km−2 a−1 on average, which is much less than values of the Indus, Ganges, and Brahmaputra draining the HQTP front, and the Amazon and Orinoco draining the Andes Mountains. However, total chemical denudation fluxes (including silicate, carbonate, and evaporite weathering) of the three rivers varied between 44.5 and 70.4 t km−2 a−1, higher than published global mean values. This may indicate more intense chemical denudation for the three rivers draining the HQTP than those in the other areas of the world.