Silicate weathering and CO 2 consumption deduced from the seven Chinese rivers originating in the Qinghai-Tibet Plateau

Abstract

We present river chemical data for the seven Chinese rivers (the Jinsha Jiang, Yalong Jiang, Min Jiang, Dadu He, Lancang Jiang, Nu Jiang and Huang He) originating in the Qinghai–Tibet Plateau. Our sampling locations are near sites where the seven rivers flow down the plateau. Water samples were collected in both high-water periods (summer) and low-water periods (winter). Our study shows that most of the Ca, Mg and HCO 3 in the seven rivers are derived from the carbonate weathering and only small fractions (10%) of the cations are derived from silicate weathering. The chemical erosion rates of silicate and carbonate range from 1.1 mm ka − 1 to 3.4 mm ka − 1 and from 7.5 mm ka − 1 to 29.9 mm ka − 1 respectively. The long term CO 2 consumption by silicate weathering in the seven Chinese river basins ranges from 0.7 × 10 5 mol km − 2 a − 1 to 3.7 × 10 5 mol km − 2 a − 1 . Based on our analysis of chemical data from the seven Chinese rivers and the previously published data of the Ganges, Brahmaputra and Indus, the main ten rivers originating in the Himalaya and Qinghai–Tibet Plateau consume 328 × 10 9 mol a − 1 of atmospheric CO 2. This is only 3.8% of the CO 2 consumption derived from global silicate weathering (8700 × 10 9 mol a − 1 ), indicating that the chemical weathering of the Himalaya and Qinghai–Tibet Plateau makes a very small contribution to the reduction of the global atmospheric CO 2 concentration.