Urbanization exacerbates riverine greenhouse gas (CO2, CH4, N2O) emissions on the Qinghai-Tibet Plateau.

As the "Asian Water Tower" and a global climate-sensitive zone, the Qinghai-Tibet Plateau (QTP) river greenhouse gas (GHG) emissions affect regional climate feedbacks and the global carbon cycle, while urbanization's impact on these emissions remains unclear. The Huangshui River Basin, the eastern QTP's largest population-carrying unit and most urbanized area, provides this study with crucial geographical significance. Based on seasonal in-situ observations and land-use analysis in the basin, we revealed the characteristics and mechanisms of GHG emissions from urban rivers on the QTP. Urban rivers were identified as GHG hotspots with average fluxes of N2O, CO2, and CH4 were 9.45 ± 4.83 μmol m-2 d-1, 10.39 ± 8.32 mmol m-2 d-1, and 0.13 ± 0.09 mmol m-2 d-1 respectively, which were 1.6, 2.3 and 3.6 times higher than those from non-urban rivers. Unique seasonal patterns were observed in the QTP: N2O and CO2 fluxes peaked in spring, driven by nutrient inputs from snowmelt, whereas CH4 emissions were higher in summer under high-temperature and low-oxygen conditions that promote methanogenesis. Structural equation modeling demonstrated that urbanization indirectly influenced N2O, CO2, and CH4 emissions by altering riverine inputs of TN, TP, salinity, and DOC. Overall, nutrient inputs exerted a strong stimulatory impact on GHG emissions, while salinity exhibited an inhibitory influence. This study fills gaps in GHG emissions within urbanized basins of the QTP and provides scientific guidance for managing GHG dynamics and guiding GHG emission reduction strategies for the ecological vulnerability of plateau watersheds undergoing rapid urbanization.