南极普里兹湾及邻近南大洋水体N_2O分布特征

利用中国第25、26次南极科学考察航次获得南极普里兹湾及邻近南大洋附近水样,采用顶空气相色谱法分析其中N_2O含量,结果表明普里兹湾陆架水体N_2O浓度较低,介于13.2―17.4 nmol·L~(-1),且呈现不饱和状态,饱和度异常值为-7%;而普里兹湾附近南大洋水体中N_2O浓度较高,介于15.5―23.3 nmol·L-1,除表面一层极薄的不饱和层外,中层至底层水体相对工业革命前大气浓度为高度过饱和状态。该区域N_2O的分布格局与复杂的水团特性和水文过程有密切关系。N_2O含量不饱和的普里兹湾陆架水(SW)和绕极深层流(CDW)混合下沉形成南极底层水(AABW),可能为温室气体N_2O提供向深层海洋输运的通路。这个过程为大气N_2O提供了一个汇的机制,使南极近岸水体成为大气N_2O的汇区。

DISTRIBUTION OF N2O in PRYDZ BAY AND ADJACENT SOUTHERN OCEAN

Water samples collected from Prydz Bay and the adjacent Southern Ocean during the 25th and 26th Chinese Antarctic Research Expeditions were analyzed for N₂O concentration using the static headspace gas chromatography method. The concentration of N₂O over the Prydz Bay continental shelf was found to be relatively low, with a range of 13.2—17.4 nmol·L^?1, and it was undersaturated compared with the current atmospheric mixing ratio, with saturation anomaly centers at ?7%. However, higher concentrations of N₂O, with a range of 15.5—23.3 nmol·L^?1, were found in the Southern Ocean. The subsurface to bottom waters all showed oversaturation against the atmospheric mixing ratio prior to the industrial revolution. It was established that the distribution pattern of N₂O within the study area was related to the complex hydrographic characteristics of the region. Prydz Bay shelf water with undersaturated N₂O might mix with Circumpolar Deep Water and sink to the bottom of the Southern Ocean, forming Antarctic Bottom Water. This could act as a pathway for N₂O transportation into deep water, providing a sink for atmospheric N₂O.