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.
Highlights
Riverine dissolved salts have many sources such as atmosphere inputs, including sea salt aerosols and rainwater; products from the chemical weathering of rocks, including silicates, carbonates, evaporites, and sulfides; and anthropogenic inputs [1]
The results showed that water in the Yarlung Tsangpo River Basin is alkaline, with a pH value of ~8.0
The mean [Ca]carbonate and [Mg]carbonate contributions were 601.7 and 227.6 μmol/L, respectively; this accounted for 55.9% (39.7%–62.7%) of the total cation content after excluding the precipitation contribution. These results demonstrated that carbonates were the major mineral type affecting the water chemistry in the Yarlung Tsangpo River Basin
Summary
Riverine dissolved salts have many sources such as atmosphere inputs, including sea salt aerosols and rainwater; products from the chemical weathering of rocks, including silicates, carbonates, evaporites, and sulfides; and anthropogenic inputs [1]. Establishing a long-term dataset of water chemistry and identifying the changes of the impacts of various natural processes on the water ionic chemistry are necessary. For this purpose, stoichiometry based on the ion content can provide simple methods (e.g., forward and inverse models) to create these datasets [9]. Stoichiometry based on the ion content can provide simple methods (e.g., forward and inverse models) to create these datasets [9] These methods have been applied in many river basins around the world [10,11,12,13,14,15]
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