Chemical weathering and its associated CO2 consumption on the Tibetan Plateau: A case of the Lhasa River Basin

In order to study chemical weathering and its effects on CO2 consumption and climate change on the Tibetan Plateau, hydrochemical data were collected bi-monthly, over a hydrological year between November 2019 to October 2020, at selected hydrological monitoring stations across the Lhasa River Basin. Combined with 513CDIC and 534Sso data, the hydrochemistry of the river basin and its major influencing factors were investigated. Mass-balance and forward-model approaches were applied to calculate the end-member contribution, chemical weathering rate, and atmospheric CO2 consumption flux in the river basin. The main ionic species in river water were Ca2+ and HCO;i~, and the hydrochemical type was HC03-Ca. The cation contribution percentages from atmospheric input, human activities, silicate weathering, and carbonate weathering were 6%, 4%, 21% and 70%, respectively. Chemical weathering is largely caused by sulfuric acid corrosion, where coal strata and sulfide deposits each contributed 50% sulfides, as evidenced by the chemical composition of river water, and 2 consumption flux were 5.20 t*km 2 -a-1 and 118 x 10J mol'km *a_1 respectively for silicate, and 22. 5 t • kirT2 • a-1 and 202 x 103 mol • kirT2 • a-1 respectively for carbonate, excluding the impact of sulfuric acid. With sulfuric acid involvement, the annualized weathering rate for car bonate increased by 31% to 29. 4 t* kirT2 • a-1, and CO2 consumption flux for carbonate and silicate combined reduced by 35% to 207 x 103 mol •kirT2 •a-1. This work revealed that sulfuric acid-mediated weathering can change the regional carbon cycle and should be taken into consideration in carbon cycling modeling. © 2023 Science Frontiers editorial department. All rights reserved.