Studies On Distrbutions And Sea-to-Air Fluxes Of Dissolved Nitrous Oxide And Methane In The South China Sea,Yellow Sea And Yangtze River Estuary

N2O and CH4 are important atmospheric trace gases, which play significant roles in the global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric N2O and CH4, especially coastal regions which appear to correlate with human activity closely, hence they are responsible for a large part of the oceanic N2O and CH4 emissions. Studies on the biogeochemistry of dissolved N2O and CH4 in different sea waters will be helpful to estimate the contribution of oceanic emissions to the atmospheric N2O and CH4 on a global scale, and to predict the influence of oceanic emissions on the global climate. In the present dissertation, distributions and fluxes of N2O and CH4 in the South China Sea (SS) , the Yellow Sea (YS) and the Yangtze River Estuaries, are studied.Distributions and fluxes of nitrous oxide and methane were determined during the survey on the northern part of SS in April- May 2005. The results show that the average nitrous oxide concentrations in the surface, 500m, 1000m and 1500m waters in the SS are 11.4±5.28, 26.6±8.14, 26.5±7.27 and 26.0±6.47 nmol/L, respectively. N2O enrichment in the deep waters is found at most stations of the SS, which underlines that there exists important sources of nitrous oxide in deep waters or bottom sediments. The distributions of nitrous oxide in the surface waters are influenced by the bottom waters transport, and the concentrations in both surface and deep layers waters appear the same distributions: nitrous oxide concentrations decrease from onshore to offshore and the lowest concentration occurs in the center of the SS. Liss and Merlivat relationship (LM86) and Wanninkhof relationship (W92) were employed to estimate the sea-to-air N2O fluxes based on the in situ wind speeds and the measured nitrous oxide concentrations in the surface waters. The results show...