Divergence characteristics and driving mechanisms of dissolved greenhouse gases in karst and non-karst reservoirs
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In the context of global climate change, the mechanisms driving reservoir greenhouse gas emissions and their responses to geological settings continue to be understudied aspects of global carbon cycle research. Focusing on typical karst (Dalongdong) and non-karst (Qingshitan) reservoirs in China, this research employs stratified sampling, in situ monitoring, and multiparameter analysis to elucidate the spatiotemporal driving mechanisms and key controlling factors of dissolved greenhouse gases (CH 4 , CO 2 , N 2 O) across different geological backgrounds. The results indicate that: (1) Both karst and non‐karst reservoirs exhibit thermal stratification during the strong and weak stratification periods, with dissolved greenhouse gas concentrations increasing markedly with depth. (2) During the strong and weak stratification periods, karst reservoirs experience a sharp increase in greenhouse gas concentrations in the bottom layer under anoxic conditions, due to the combined effects of thermal stratification, carbonate dissolution, groundwater recharge, and water body bio-metabolic activity; in contrast, the accumulation of greenhouse gases in the bottom layer of non-karst reservoirs is primarily regulated by biological metabolism and nitrogen cycling processes. (3) PCA reveals that greenhouse gas concentrations in karst reservoirs are primarily governed by the CO 2 -HCO 3 - -CO 3 2- -CaCO 3 carbonate equilibrium system, along with secondary contributions from nutrients and biological processes, whereas in non-karst reservoirs, they are dictated by the oxidizing conditions of the water and nitrogen cycling, further affected by salinity and temperature-driven nutrient and algal dynamics. This study reveals the spatiotemporal differences in reservoir greenhouse gas concentrations and their key driving mechanisms under different geological backgrounds, providing theoretical support for a deeper understanding of reservoir carbon cycling and ecological environmental management.
