资源环境科技发展态势分析平台

The river‐reservoir continuum drives a separation of sedimentation along the longitudinal hydrodynamic gradients, potentially causing imbalanced stoichiometric sedimentation. However, there are still uncertainties regarding the contribution of imbalanced stoichiometric sedimentation to methane emissions along this continuum. A two‐year field survey and in situ experiments were conducted in China's Three Gorges Reservoir (TGR), a river‐valley dammed reservoir. Sediments were trapped and collected to analyze for particulate carbon (C), nitrogen (N) and phosphorus (P) concentrations of different sizes in the summer flooded and winter dry seasons along the main stem. Large amount of sediments were deposited in the mid‐part of the TGR, particularly in the summer flood season. Hydrodynamic gradients structured imbalanced stoichiometric sedimentation patterns. Averaged particulate C:N:P proportions in the sediment layer along the upper, mid and lower part of the TGR in the first 30 years of reservoir operation were estimated to be 68:7:1, 97:8:1, 151:13:1 respectively. The mid‐part of the TGR, being the “control point" of methane accumulation based on seasons, exhibited the shift in stoichiometry and the stable isotope signatures indicating that there was likely a shift in sources of POM. P, specifically in smaller size particles (<10 μm), seemed to be the potential key driver that regulates particulate C:N:P in the sediment of the TGR. Its sedimentation, primarily in the mid‐part of the TGR, contributed to the significant decreases in particulate C/P ratios, and could possibly regulate long‐term CH₄ accumulation in the reservoir.