秋、冬季渤海溶解N_(2)O的分布和通量及其影响因素

Distributions and fluxes of dissolved nitrous oxide in the Bohai Sea in autumn and winter and their influencing factors

通过2019年10月和12月对渤海海域进行的调查及样品采集,分析溶解N_(2)O的分布和影响因素,并估算其海-气交换通量。结果表明:秋季表层海水溶解N_(2)O浓度为(8.2±0.5)nmol/L,饱和度为(97.5±4.7)%;冬季浓度为(11.0±0.8)nmol/L,饱和度为(93.8±4.5)%。渤海表层海水溶解N_(2)O浓度呈现明显的季节性差异,冬季浓度高于秋季,且高值区均集中在黄河口以及莱州湾附近。秋季渤海溶解N_(2)O处于接近饱和状态,冬季则处于不饱和状态。温度、陆源淡水输入以及沉积物-水界面交换对渤海溶解N_(2)O的分布有重要影响。2019年10月和12月黄河向渤海输入N_(2)O的量分别约为4.2×10^(4)mol和1.1×10^(4)mol,是渤海N_(2)O的重要来源,而秋、冬季渤海底层的沉积物既可能是渤海水体N_(2)O的源,也可能是其汇。秋季和冬季渤海N_(2)O海-气交换通量分别为(-0.3±0.7)μmol/(m^(2)·d)和(-1.1±1.6)μmol/(m^(2)·d),与其他已报道海域相比,渤海N_(2)O的海-气交换通量较低。初步估算秋季和冬季两季节渤海从大气吸收N_(2)O的量为4.41×10^(-4)Tg,是大气N_(2)O的汇。

Distributions and air-sea fluxes of dissolved N_(2)O in the Bohai Sea were investigated in October and December 2019. Dissolved N_(2)O concentrations in surface waters were(8.2±0.5) nmol/L [(97.5%±4.7)%saturation] in autumn and(11.0±0.8) nmol/L [(93.8±4.5)% saturation] in winter. Generally, surface N_(2)O concentrations in winter were higher than in autumn. High N_(2)O concentrations were observed mainly near the Yellow River Estuary and Laizhou bay. N_(2)O in the Bohai Sea was close to saturation in autumn and undersaturated in winter. Temperature, riverine input and sediment-water exchange are major factors affecting distributions of dissolved N_(2)O in the Bohai Sea. The freshwater input from the Yellow River was an important source of N_(2)O in the Bohai Sea, with fluxes of about 4.2×10^(4) mol in October 2019 and 1.1×10^(4) mol in December 2019. Sediment can act as either a source or a sink of water column N_(2)O in autumn and winter. The air-sea fluxes of the Bohai Sea were about(-0.3±0.7) μmol/(m^(2)·d) in autumn and(-1.1±1.6) μmol/(m^(2)·d) in winter, and were lower than from other coastal seas of China. The Bohai Sea acted as a N_(2)O sink of the atmosphere in autumn and winter with a total influx of 4.41×10^(-4)Tg.