Study on the release fluxes of carbon source gases under different operating conditions in the middle reach of the main stream of the Three Gorges Reservoir
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Abstract:
The input of large quantities of organic carbon sources from the land, and the discharge of carbon sources such as CO2 and CH4 caused by the operation and damming in the Three Gorges Reservoir Area have become the hot spots of recent research. In order to reveal the variation characteristics of CO2 and CH4 concentrations in different flow levels in the Three Gorges Reservoir Area, this study took the middle reach of the main stream of the Three Gorges Reservoir as the research objects. Samples were taken from Zhongxian County (ZX), Wanzhou (WZ), Fuling (FL)monthly from August 2017 to November 2018 to analyze and study the characteristics of CO2 and CH4 fluxes at the water-air interface under different operating conditions. Results showed that during the research period, CO2concentration of the ZX, WZ and FL was between 0.008 6 mmol/L and 0.115 3 mmol/L, 0.003 5 mmol/L and 0.116 8 mmol/L, and 0.006 3 mmol/L and 0.098 6 mmol/L, respectively. The concentration of CO2 at these three sampling points tended to be consistent and reached its peak during the drain period from April to May and its lowest point in the low water level operation period from June to September. CH4 flux exhibited the feature of a sink during the operation at a low water level, but at FL it reached the maximum value as a source in the discharge period. The CO2 fluxes at the three locations showed the feature of a source during the discharge period, but during low water level operation period, CO2 flux indicated the switch between a source and a sink. CO2 flux was at a medium level and CH4 flux was at a lower-middle level compared with those of other reservoirs in the world.
