Diffusive greenhouse gases fluxes from the surface of the Three Gorges Reservoir: Study at a site in Fuling

To investigate the water-air diffusive greenhouse gases (GHGs) fluxes from the Three Gorges Reservoir (TGR), a field experiment on carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes from water surface was carried out from March 2011 to August 2012 by floating static chamber method. The results showed that CO₂ was released to the atmosphere all the time and was less in autumn than in other seasons (P < 0.05). CH₄ was also released to the atmosphere throughout the year but more in summer than other three seasons (P < 0.05). N₂O flux was higher in autumn than other seasons (P < 0.05), and N₂O was absorbed from the atmosphere mainly in summer. Moreover, correlation analysis illustrated that CO₂ flux had significantly negative correlation with wind velocity (P < 0.05), whereas positive correlation with pH (P < 0.01) had been found. There was no significant correlation between CH₄ (or N₂O) flux and the measured environmental variables respectively (P > 0.05). Additionally, the annual fluxes of CO₂, CH₄ and N₂O were 140.45 ± 12.57 mg CO₂·m^?2 h^?1, 1.35 ± 0.14 mg CH₄·m^?2 h^?1 and 34.34 ± 11.64 μg N₂O·m^?2 h^?1, respectively. When compared to other reservoirs worldwide, the CO₂ and N₂O fluxes from TGR were higher than those from boreal and temperate reservoirs, but much lower than those from tropical reservoirs. CH₄ flux was lower than those from boreal, temperate and most tropical reservoirs. In our study, the surface area of the TGR emitted 1.42 × 10⁶ t CO₂, 1.19 × 10⁴ t CH₄ and 589.93 t N₂O in a year. The total GWP was 17.68 t CO₂-eq ha^?1 yr^?1, of which CO₂ flux was dominant (74.38%). Therefore, CO₂ was the main contributor of GHGs fluxes in our study and thus future researches should focus on how to reduce CO₂ fluxes from the surface of the TGR. TGR has a considerable contribution to regional GHG emissions.