长江口潮滩湿地-大气界面碳通量特征

Characteristics of carbon fluxes through intertidal flat wetland-atmosphere interface of Yangtze estuary

选择长江河口崇明东滩为典型研究区域,使用原位静态箱-气相色谱法,对长江河口潮滩湿地-大气界面碳通量(CH4和CO2)进行了为期一年的现场观测实验.结果表明,观测期内,崇明东滩低潮滩(CM-3)表现为碳的吸收汇,平均碳通量为-13.23mg·m-·2h-1,且有明显的变化特征,8月为碳吸收的高峰期,2月碳的通量值最低;虽然低潮滩CH4年平均排放通量仅为0.04mg·m-2·h-1,在碳通量中所占比例很小,但却是大气CH4的持续排放源.中潮滩(CM-2)为大气CH4的排放源,在7月达到排放高峰;对CO2而言,光照条件下(明箱)以吸收为主,而无光照时(暗箱)中潮滩是CO2的排放源.中潮滩湿地-大气界面碳的年平均交换通量为51.79mg·m-·2h-1,显著高于低潮滩,植被和有机质含量的不同是导致两者差异的主要原因.温度和光照是影响碳通量及其季节变化的重要因素.海三棱藨草植株和中、低潮滩藻类的光合作用均显著促进了潮滩对大气碳的吸收.

Using static closed chamber-GC technique, carbon （CH4 and CO2） fluxes through intertidal flat wetland-atmosphere interface of the Yangtze estuary were measured continuously for one year at Chongming east intertidal flat （CM）. The results showed that, the low tidal-flat of CM （CM-3） was the sink of carbon, its average flux was -13.23 mg·m^-2·h^-1, and carbon flux had significant variation characteristics, the maximum and minimum carbon uptake flux were in August and February respectively. Although the average emission flux of CH4 from CM-3 occupied little proportion of the carbon flux, CM-3 sediment was the continual source of atmospheric methane. The middle tidal-flat of CM （ CM-2 ） was source of atmospheric methane and the maximum emission flux occurred in July; Carbon dioxide were uptaked under sunshine condition and emitted in darkness; average carbon flux through wetland-atmosphere interface was 51.79 mg·m^-2·h^-1 in CM-2. It was higher than in CM-3 observably all-year because of difference of vegetation and contents of sediment organic carbon. Temperature and sunshine intensity are major impact factors which control the carbon fluxes and their variation. The photosynthesis of both Scirpus mariqueter and benthos alga evidently increased uptake of carbon.