[Comparative study on water-air CO2, CH4 flux in two tributaries in the Three Gorges Reservoir, China]

The Three Gorges Reservoir (TGR) is a huge reservoir under the subtropical climate condition. It shows great spatio-temporal heterogeneity on biogeochemical cycling of carbon in the TGR's aquatic ecosystem. 1 a field monitoring on water-air CO2 and CH4 fluxes was conducted from June, 2010 to May, 2011 in Longxi River and Pengxi River, the 2 typical tributaries in the Three Gorges Reservoir. Comparative study showed that annual CO2 diffusive fluxes in the Longxi River and Pengxi River were (7.30 +/- 1.89) mmol x (m2 x h)(-1) and (0.71 +/- 0.46) mmol x (m2 x h)(-1), respectively, and the CH4 diffusive fluxes were (0.11 +/- 0.095) mmol x (m2 x h)(-1) and (0.007 4 +/- 0.001 7) mmol x (m2 x h)(-1). Higher intensities and seasonal variance of CO2 and CH4 fluxes were observed in Longxi River compared to those in Pengxi River. Through a comparative analysis of the environmental and watershed parameters in both rivers, it was found that the unstable hydraulic conditions and habitat of Longxi River prohibited the growth of phytoplankton, reducing its capability of carbon assimilation. The higher pollution load in the basin and the higher organic matters and total nitrogen in the impounding soil of Longxi River also resulted in the higher level of greenhouse gas fluxes compared to those in the Pengxi River. More studies shall be conducted to elucidate the variance of CH4 flux and its controlling factors in both rivers.