冬季九龙江河口表层水体N_2O分布特征及海气通量的初步研究

Distribution of N_2O in the Jiulongjiang River Estuary and estimation of its air-sea flux during winter

氧化亚氮（N2O）因其强温室效应和潜在的臭氧破坏作用备受关注.大量研究显示河口区域,特别是人为氮源输入影响严重的区域是N2O的重要源区.随着氮肥施用量的快速增加,中国大陆河口区域对全球N2O收支势必有较大的贡献.本文研究了2009年冬季九龙江口表层水N2O浓度的分布特征及其影响因素,并评估了其海气通量.研究结果显示,冬季九龙江河口表层水体N2O浓度从盐度低至0.3时的81.7±1.7 nmol/dm3下降至盐度为27.2时的14.1±0.2 nmol/dm3,相应盐度下其饱和度分别为754%和138%;九龙江河口为大气N2O的强源区.与NO3-N、NO2-N、NH4-N等营养盐浓度的分布特征相比较可推测,2009年冬季N2O在九龙江河口的混合过程中呈不保守状态,部分N2O可能通过海气混合过程从水体迁移出.N2O的海气通量呈由高盐处向低盐处递增的趋势,变化范围在3~94μmol/（m2.d）之间.

N2O is considered as one of the most important greenhouse gases and also has the potential to deplete stratospheric ozone.Estuaries,especially those affected by human activity,are regarded as potential sources of atmospheric N2O.N2O in surface water was sampled at seven stations in the winter of 2009 along the south coast of the Jiulongjiang River Estuary,and a gas chromatograph was employed to analyze the concentration of N2O and the concentrations of DO and nutrients（NO3-N,NO2 N,NH4-N） were also measured.This work offers a snapshot of the N2O concentration and distribution characteristics for the Jiulongjiang River Estuary and its relationship with biogenic elements,and assesses the air-sea flux of N2O.The results show that the concentration of N2O in the Jiulongjiang River Estuary decreases from 81.7±1.7 nmol/dm3（754% saturation） at salinity of 0.3 to 14.1±0.2 nmol/dm3（138% saturation） at salinity of 27.2 in winter.Comparing with the distribution of nutrients,it is seen that N2O mixing is non-conservative,and air-sea exchange is a mechanism for the removal of N2O.The study area behaves as a significant N2O source.Air-sea flux has a progressive trend from a high-salinity area to a low-salinity area,ranging from 3 to 94 μmol/（m2·d）.