Change of Contributions from Different Natural Processes to the Ionic Budget in the Yarlung Tsangpo River

Abstract

Understanding the geochemistry of natural waters is helpful for grasping how the water environment responds to climate and environment changes. The basin of the Yarlung Tsangpo River, the most important river in the Tibetan Plateau, was selected as the study area. Based on our field sampling data and the previously published data of major ions in the river, we distinguished the different sources of the riverine ionic budget. Subsequently, the changes in their contributions were determined over the past four decades. The results indicate that carbonate weathering was the main source of the dissolved ions in the Yarlung Tsangpo River. Consequently, an increasing trend was found in the Ca2+, Mg2+, and HCO3− concentrations in the river water. Conversely, silicate weathering, the secondary source of ions, declined after 2000. More notably, the sulfide oxidation process was considerably enhanced over the study period, which resulted in a two-fold increase in SO42− in the riverine water.