Air-water CO2 Exchange Fluxes and Its Controlling Mechanism in Modaomen Estuary of the Pearl River, China

The seasonal and spatial characterization of dissolved CO2 and its control mechanism in the Modaomen Estuary of the Pearl River (China) were determined by the four underway surveys in April, July, October 2013 and January 2014, respectively. The partial pressure of carbon dioxide (pCO(2) ) was various among different seasons, which may be attributed to the variational runoff among wet and dry seasons. The pCO(2) is wet season (April and July) was greatly higher than that of dry season (October and January). The runoff may be regarded as the mainly source of CO2 in the estuary, while the contribution of in situ biologic respiration in the estuary may be limited. The outgassing fluxes of CO2 in the Modaomen Estuary were approximately 30.80 mol C m(-2) yr(-1). Approximately 2% dissolved inorganic carbon (DIC) in the runoff was emitted into atmosphere during transportation processes in the estuary. The runoff was the key factor for the seasonal variation of CO2 outgassing fluxes in the Modaomen Estuary.