Distributions and sea-to-air fluxes of methane and nitrous oxide in the North East China Sea in summer

The methane (CH4) and nitrous oxide (N2O) in the north East China Sea were measured during September 5 to 25 of 2003. The vertical profiles of CH4 along four sections of the East China Sea showed high spatial variability due to the influence of complex water masses and the variable controlling factors. The vertical profiles of N2O were less variable and were characterized by an increase from the surface to the bottom water, and were influenced mainly by the hydrographic conditions and biological production. CH4 saturations in the surface waters ranged from 148% to 2490% with the average of 487 ± 555%, while the N2O saturations ranged from 94% to 382% with an average of 191 ± 74%. The sea-to-air CH4 fluxes were estimated to be 20.9 ± 54.8 µmol m− 2 d− 1 using the LM86 equations, and 36.3 ±95.7 µmol m− 2 d− 1 using the W92 equation. The sea-to-air N2O fluxes were estimated to be 9.8 ± 16.0 µmol m− 2 d− 1 using the LM86 equations and 17.1 ± 26.4 µmol m− 2 d− 1 using the W92 equation. Both the saturations and fluxes of CH4 and N2O showed obvious spatial variations, which furthermore suggests that the northern region of the East China Sea is a net source of atmospheric CH4 and N2O.