Methane Oxidation in the Water Column of Xiangxi Bay, Three Gorges Reservoir

Four field campaigns are carried out to quantify the methane (CH 4 ) oxidation rate in Xiangxi Bay (XXB) of the Three Gorges Reservoir (TGR), China. The water depth of the sampling site varied from 13 to 30 m resulting from the water level fluctuation of the TGR. The CH 4 oxidation rates are measured in situ as the decline of dissolved CH 4 concentration versus time in incubated, and those rates. The CH 4 oxidation rates range from 1.18 × 10 −3 to 3.69 × 10 −3  µmol L −1  h −1 , with higher values and stronger variation during summer. A static floating chamber method is used to measure CH 4 emitted to the atmosphere resulting in an annual mean flux of 4.79 µmol m −2  h −1 . The CH 4 emission rate is significantly negatively correlated with the water level. The results show that a large fraction of CH 4 is consumed in the water column with a range of 28.97–55.90 µmol m −2  h −1 , accounting for ≈69–98% of the total CH 4 input into the water column, and more than 90% is consumed outside the summer, when the water level is lowest. Water depth, which is dominated by water level of the TGR, is a potentially important driver for CH 4 oxidation and atmospheric emission in the tributary bay.