Understanding how inland lake system environmental gradients on the Qinghai-Tibet Plateau impact the geographical patterns of carbon and water sources or sink

On the Qinghai-Tibet Plateau (QTP), salinity, area, and altitude are the three main environmental gradients, and they are also likely to be the main influencing factors of lake water and carbon (C) sources. We collected water samples from lake and river systems on the QTP to determine their associative physical, chemical, biological, and isotopic indicators. Firstly, the ionic composition of individual lake systems on the QTP varied significantly, and evaporation was the main controlling factor respective to most of their chemical characteristics. Secondly, glacial meltwater (8%), rainwater (26%), soil water (28%), and the evaporation effect (38%) were the main controlling factors of lake water on the QTP. Atmospheric exchange (72%), soil organic matter (SOM) (1%), and rock weathering (19%) were the main dissolved inorganic carbon (DIC) sources of lake water on the QTP. Thirdly, salinity and altitude were the main influencing factors of lake water and C sources, especially salinity. Findings from this study are intended to supplement the knowledge base on C and water coupling effects in plateau lake systems while also improving our understanding on the response of inland lake systems to climate change globally.